WorldWideScience

Sample records for underlying test statistics

  1. Empirical Statistical Power for Testing Multilocus Genotypic Effects under Unbalanced Designs Using a Gibbs Sampler

    Directory of Open Access Journals (Sweden)

    Chaeyoung Lee

    2012-11-01

    Full Text Available Epistasis that may explain a large portion of the phenotypic variation for complex economic traits of animals has been ignored in many genetic association studies. A Baysian method was introduced to draw inferences about multilocus genotypic effects based on their marginal posterior distributions by a Gibbs sampler. A simulation study was conducted to provide statistical powers under various unbalanced designs by using this method. Data were simulated by combined designs of number of loci, within genotype variance, and sample size in unbalanced designs with or without null combined genotype cells. Mean empirical statistical power was estimated for testing posterior mean estimate of combined genotype effect. A practical example for obtaining empirical statistical power estimates with a given sample size was provided under unbalanced designs. The empirical statistical powers would be useful for determining an optimal design when interactive associations of multiple loci with complex phenotypes were examined.

  2. 100 statistical tests

    CERN Document Server

    Kanji, Gopal K

    2006-01-01

    This expanded and updated Third Edition of Gopal K. Kanji's best-selling resource on statistical tests covers all the most commonly used tests with information on how to calculate and interpret results with simple datasets. Each entry begins with a short summary statement about the test's purpose, and contains details of the test objective, the limitations (or assumptions) involved, a brief outline of the method, a worked example, and the numerical calculation. 100 Statistical Tests, Third Edition is the one indispensable guide for users of statistical materials and consumers of statistical information at all levels and across all disciplines.

  3. Statistical Indexes for Monitoring Item Behavior under Computer Adaptive Testing Environment.

    Science.gov (United States)

    Zhu, Renbang; Yu, Feng; Liu, Su

    A computerized adaptive test (CAT) administration usually requires a large supply of items with accurately estimated psychometric properties, such as item response theory (IRT) parameter estimates, to ensure the precision of examinee ability estimation. However, an estimated IRT model of a given item in any given pool does not always correctly…

  4. Testing statistical hypotheses

    CERN Document Server

    Lehmann, E L

    2005-01-01

    The third edition of Testing Statistical Hypotheses updates and expands upon the classic graduate text, emphasizing optimality theory for hypothesis testing and confidence sets. The principal additions include a rigorous treatment of large sample optimality, together with the requisite tools. In addition, an introduction to the theory of resampling methods such as the bootstrap is developed. The sections on multiple testing and goodness of fit testing are expanded. The text is suitable for Ph.D. students in statistics and includes over 300 new problems out of a total of more than 760. E.L. Lehmann is Professor of Statistics Emeritus at the University of California, Berkeley. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences, and the recipient of honorary degrees from the University of Leiden, The Netherlands and the University of Chicago. He is the author of Elements of Large-Sample Theory and (with George Casella) he is also the author of Theory of Point Estimat...

  5. Statistical test of anarchy

    International Nuclear Information System (INIS)

    Gouvea, Andre de; Murayama, Hitoshi

    2003-01-01

    'Anarchy' is the hypothesis that there is no fundamental distinction among the three flavors of neutrinos. It describes the mixing angles as random variables, drawn from well-defined probability distributions dictated by the group Haar measure. We perform a Kolmogorov-Smirnov (KS) statistical test to verify whether anarchy is consistent with all neutrino data, including the new result presented by KamLAND. We find a KS probability for Nature's choice of mixing angles equal to 64%, quite consistent with the anarchical hypothesis. In turn, assuming that anarchy is indeed correct, we compute lower bounds on vertical bar U e3 vertical bar 2 , the remaining unknown 'angle' of the leptonic mixing matrix

  6. Testing statistical hypotheses of equivalence

    CERN Document Server

    Wellek, Stefan

    2010-01-01

    Equivalence testing has grown significantly in importance over the last two decades, especially as its relevance to a variety of applications has become understood. Yet published work on the general methodology remains scattered in specialists' journals, and for the most part, it focuses on the relatively narrow topic of bioequivalence assessment.With a far broader perspective, Testing Statistical Hypotheses of Equivalence provides the first comprehensive treatment of statistical equivalence testing. The author addresses a spectrum of specific, two-sided equivalence testing problems, from the

  7. Statistical tests to compare motif count exceptionalities

    Directory of Open Access Journals (Sweden)

    Vandewalle Vincent

    2007-03-01

    Full Text Available Abstract Background Finding over- or under-represented motifs in biological sequences is now a common task in genomics. Thanks to p-value calculation for motif counts, exceptional motifs are identified and represent candidate functional motifs. The present work addresses the related question of comparing the exceptionality of one motif in two different sequences. Just comparing the motif count p-values in each sequence is indeed not sufficient to decide if this motif is significantly more exceptional in one sequence compared to the other one. A statistical test is required. Results We develop and analyze two statistical tests, an exact binomial one and an asymptotic likelihood ratio test, to decide whether the exceptionality of a given motif is equivalent or significantly different in two sequences of interest. For that purpose, motif occurrences are modeled by Poisson processes, with a special care for overlapping motifs. Both tests can take the sequence compositions into account. As an illustration, we compare the octamer exceptionalities in the Escherichia coli K-12 backbone versus variable strain-specific loops. Conclusion The exact binomial test is particularly adapted for small counts. For large counts, we advise to use the likelihood ratio test which is asymptotic but strongly correlated with the exact binomial test and very simple to use.

  8. Statistical hypothesis testing with SAS and R

    CERN Document Server

    Taeger, Dirk

    2014-01-01

    A comprehensive guide to statistical hypothesis testing with examples in SAS and R When analyzing datasets the following questions often arise:Is there a short hand procedure for a statistical test available in SAS or R?If so, how do I use it?If not, how do I program the test myself? This book answers these questions and provides an overview of the most commonstatistical test problems in a comprehensive way, making it easy to find and performan appropriate statistical test. A general summary of statistical test theory is presented, along with a basicdescription for each test, including the

  9. Nonparametric Statistics Test Software Package.

    Science.gov (United States)

    1983-09-01

    25 I1l,lCELL WRITE (NCF,12 ) IvE (I ,RCCT(I) 122 FORMAT(IlXt 3(H5 9 1) IF( IeLT *NCELL) WRITE (NOF1123 J PARTV(I1J 123 FORMAT( Xll----’,FIo.3J 25 CONT...the user’s entries. Its purpose is to write two types of files needed by the program Crunch: the data file, and the option file. 211 Iuill rateLchiavar...data file and communicate the choice of test and test parameters to Crunch. After a data file is written, Lochinvar prompts the writing of the

  10. Improvement of Statistical Decisions under Parametric Uncertainty

    Science.gov (United States)

    Nechval, Nicholas A.; Nechval, Konstantin N.; Purgailis, Maris; Berzins, Gundars; Rozevskis, Uldis

    2011-10-01

    A large number of problems in production planning and scheduling, location, transportation, finance, and engineering design require that decisions be made in the presence of uncertainty. Decision-making under uncertainty is a central problem in statistical inference, and has been formally studied in virtually all approaches to inference. The aim of the present paper is to show how the invariant embedding technique, the idea of which belongs to the authors, may be employed in the particular case of finding the improved statistical decisions under parametric uncertainty. This technique represents a simple and computationally attractive statistical method based on the constructive use of the invariance principle in mathematical statistics. Unlike the Bayesian approach, an invariant embedding technique is independent of the choice of priors. It allows one to eliminate unknown parameters from the problem and to find the best invariant decision rule, which has smaller risk than any of the well-known decision rules. To illustrate the proposed technique, application examples are given.

  11. Statistical decisions under nonparametric a priori information

    International Nuclear Information System (INIS)

    Chilingaryan, A.A.

    1985-01-01

    The basic module of applied program package for statistical analysis of the ANI experiment data is described. By means of this module tasks of choosing theoretical model most adequately fitting to experimental data, selection of events of definte type, identification of elementary particles are carried out. For mentioned problems solving, the Bayesian rules, one-leave out test and KNN (K Nearest Neighbour) adaptive density estimation are utilized

  12. The insignificance of statistical significance testing

    Science.gov (United States)

    Johnson, Douglas H.

    1999-01-01

    Despite their use in scientific journals such as The Journal of Wildlife Management, statistical hypothesis tests add very little value to the products of research. Indeed, they frequently confuse the interpretation of data. This paper describes how statistical hypothesis tests are often viewed, and then contrasts that interpretation with the correct one. I discuss the arbitrariness of P-values, conclusions that the null hypothesis is true, power analysis, and distinctions between statistical and biological significance. Statistical hypothesis testing, in which the null hypothesis about the properties of a population is almost always known a priori to be false, is contrasted with scientific hypothesis testing, which examines a credible null hypothesis about phenomena in nature. More meaningful alternatives are briefly outlined, including estimation and confidence intervals for determining the importance of factors, decision theory for guiding actions in the face of uncertainty, and Bayesian approaches to hypothesis testing and other statistical practices.

  13. Similar tests and the standardized log likelihood ratio statistic

    DEFF Research Database (Denmark)

    Jensen, Jens Ledet

    1986-01-01

    When testing an affine hypothesis in an exponential family the 'ideal' procedure is to calculate the exact similar test, or an approximation to this, based on the conditional distribution given the minimal sufficient statistic under the null hypothesis. By contrast to this there is a 'primitive......' approach in which the marginal distribution of a test statistic considered and any nuisance parameter appearing in the test statistic is replaced by an estimate. We show here that when using standardized likelihood ratio statistics the 'primitive' procedure is in fact an 'ideal' procedure to order O(n -3...

  14. Polarimetric Segmentation Using Wishart Test Statistic

    DEFF Research Database (Denmark)

    Skriver, Henning; Schou, Jesper; Nielsen, Allan Aasbjerg

    2002-01-01

    A newly developed test statistic for equality of two complex covariance matrices following the complex Wishart distribution and an associated asymptotic probability for the test statistic has been used in a segmentation algorithm. The segmentation algorithm is based on the MUM (merge using moments......) approach, which is a merging algorithm for single channel SAR images. The polarimetric version described in this paper uses the above-mentioned test statistic for merging. The segmentation algorithm has been applied to polarimetric SAR data from the Danish dual-frequency, airborne polarimetric SAR, EMISAR...

  15. Teaching Statistics in Language Testing Courses

    Science.gov (United States)

    Brown, James Dean

    2013-01-01

    The purpose of this article is to examine the literature on teaching statistics for useful ideas that teachers of language testing courses can draw on and incorporate into their teaching toolkits as they see fit. To those ends, the article addresses eight questions: What is known generally about teaching statistics? Why are students so anxious…

  16. A simplification of the likelihood ratio test statistic for testing ...

    African Journals Online (AJOL)

    The traditional likelihood ratio test statistic for testing hypothesis about goodness of fit of multinomial probabilities in one, two and multi – dimensional contingency table was simplified. Advantageously, using the simplified version of the statistic to test the null hypothesis is easier and faster because calculating the expected ...

  17. SPSS for applied sciences basic statistical testing

    CERN Document Server

    Davis, Cole

    2013-01-01

    This book offers a quick and basic guide to using SPSS and provides a general approach to solving problems using statistical tests. It is both comprehensive in terms of the tests covered and the applied settings it refers to, and yet is short and easy to understand. Whether you are a beginner or an intermediate level test user, this book will help you to analyse different types of data in applied settings. It will also give you the confidence to use other statistical software and to extend your expertise to more specific scientific settings as required.The author does not use mathematical form

  18. A Statistical Perspective on Highly Accelerated Testing

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Edward V. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-01

    Highly accelerated life testing has been heavily promoted at Sandia (and elsewhere) as a means to rapidly identify product weaknesses caused by flaws in the product's design or manufacturing process. During product development, a small number of units are forced to fail at high stress. The failed units are then examined to determine the root causes of failure. The identification of the root causes of product failures exposed by highly accelerated life testing can instigate changes to the product's design and/or manufacturing process that result in a product with increased reliability. It is widely viewed that this qualitative use of highly accelerated life testing (often associated with the acronym HALT) can be useful. However, highly accelerated life testing has also been proposed as a quantitative means for "demonstrating" the reliability of a product where unreliability is associated with loss of margin via an identified and dominating failure mechanism. It is assumed that the dominant failure mechanism can be accelerated by changing the level of a stress factor that is assumed to be related to the dominant failure mode. In extreme cases, a minimal number of units (often from a pre-production lot) are subjected to a single highly accelerated stress relative to normal use. If no (or, sufficiently few) units fail at this high stress level, some might claim that a certain level of reliability has been demonstrated (relative to normal use conditions). Underlying this claim are assumptions regarding the level of knowledge associated with the relationship between the stress level and the probability of failure. The primary purpose of this document is to discuss (from a statistical perspective) the efficacy of using accelerated life testing protocols (and, in particular, "highly accelerated" protocols) to make quantitative inferences concerning the performance of a product (e.g., reliability) when in fact there is lack-of-knowledge and uncertainty concerning

  19. Teratology testing under REACH.

    Science.gov (United States)

    Barton, Steve

    2013-01-01

    REACH guidelines may require teratology testing for new and existing chemicals. This chapter discusses procedures to assess the need for teratology testing and the conduct and interpretation of teratology tests where required.

  20. Statistical treatment of fatigue test data

    International Nuclear Information System (INIS)

    Raske, D.T.

    1980-01-01

    This report discussed several aspects of fatigue data analysis in order to provide a basis for the development of statistically sound design curves. Included is a discussion on the choice of the dependent variable, the assumptions associated with least squares regression models, the variability of fatigue data, the treatment of data from suspended tests and outlying observations, and various strain-life relations

  1. Statistical test theory for the behavioral sciences

    CERN Document Server

    de Gruijter, Dato N M

    2007-01-01

    Since the development of the first intelligence test in the early 20th century, educational and psychological tests have become important measurement techniques to quantify human behavior. Focusing on this ubiquitous yet fruitful area of research, Statistical Test Theory for the Behavioral Sciences provides both a broad overview and a critical survey of assorted testing theories and models used in psychology, education, and other behavioral science fields. Following a logical progression from basic concepts to more advanced topics, the book first explains classical test theory, covering true score, measurement error, and reliability. It then presents generalizability theory, which provides a framework to deal with various aspects of test scores. In addition, the authors discuss the concept of validity in testing, offering a strategy for evidence-based validity. In the two chapters devoted to item response theory (IRT), the book explores item response models, such as the Rasch model, and applications, incl...

  2. Simplified Freeman-Tukey test statistics for testing probabilities in ...

    African Journals Online (AJOL)

    This paper presents the simplified version of the Freeman-Tukey test statistic for testing hypothesis about multinomial probabilities in one, two and multidimensional contingency tables that does not require calculating the expected cell frequencies before test of significance. The simplified method established new criteria of ...

  3. New Graphical Methods and Test Statistics for Testing Composite Normality

    Directory of Open Access Journals (Sweden)

    Marc S. Paolella

    2015-07-01

    Full Text Available Several graphical methods for testing univariate composite normality from an i.i.d. sample are presented. They are endowed with correct simultaneous error bounds and yield size-correct tests. As all are based on the empirical CDF, they are also consistent for all alternatives. For one test, called the modified stabilized probability test, or MSP, a highly simplified computational method is derived, which delivers the test statistic and also a highly accurate p-value approximation, essentially instantaneously. The MSP test is demonstrated to have higher power against asymmetric alternatives than the well-known and powerful Jarque-Bera test. A further size-correct test, based on combining two test statistics, is shown to have yet higher power. The methodology employed is fully general and can be applied to any i.i.d. univariate continuous distribution setting.

  4. Analysis of Preference Data Using Intermediate Test Statistic Abstract

    African Journals Online (AJOL)

    PROF. O. E. OSUAGWU

    2013-06-01

    Jun 1, 2013 ... West African Journal of Industrial and Academic Research Vol.7 No. 1 June ... Keywords:-Preference data, Friedman statistic, multinomial test statistic, intermediate test statistic. ... new method and consequently a new statistic ...

  5. Comparing statistical tests for detecting soil contamination greater than background

    International Nuclear Information System (INIS)

    Hardin, J.W.; Gilbert, R.O.

    1993-12-01

    The Washington State Department of Ecology (WSDE) recently issued a report that provides guidance on statistical issues regarding investigation and cleanup of soil and groundwater contamination under the Model Toxics Control Act Cleanup Regulation. Included in the report are procedures for determining a background-based cleanup standard and for conducting a 3-step statistical test procedure to decide if a site is contaminated greater than the background standard. The guidance specifies that the State test should only be used if the background and site data are lognormally distributed. The guidance in WSDE allows for using alternative tests on a site-specific basis if prior approval is obtained from WSDE. This report presents the results of a Monte Carlo computer simulation study conducted to evaluate the performance of the State test and several alternative tests for various contamination scenarios (background and site data distributions). The primary test performance criteria are (1) the probability the test will indicate that a contaminated site is indeed contaminated, and (2) the probability that the test will indicate an uncontaminated site is contaminated. The simulation study was conducted assuming the background concentrations were from lognormal or Weibull distributions. The site data were drawn from distributions selected to represent various contamination scenarios. The statistical tests studied are the State test, t test, Satterthwaite's t test, five distribution-free tests, and several tandem tests (wherein two or more tests are conducted using the same data set)

  6. Kepler Planet Detection Metrics: Statistical Bootstrap Test

    Science.gov (United States)

    Jenkins, Jon M.; Burke, Christopher J.

    2016-01-01

    This document describes the data produced by the Statistical Bootstrap Test over the final three Threshold Crossing Event (TCE) deliveries to NExScI: SOC 9.1 (Q1Q16)1 (Tenenbaum et al. 2014), SOC 9.2 (Q1Q17) aka DR242 (Seader et al. 2015), and SOC 9.3 (Q1Q17) aka DR253 (Twicken et al. 2016). The last few years have seen significant improvements in the SOC science data processing pipeline, leading to higher quality light curves and more sensitive transit searches. The statistical bootstrap analysis results presented here and the numerical results archived at NASAs Exoplanet Science Institute (NExScI) bear witness to these software improvements. This document attempts to introduce and describe the main features and differences between these three data sets as a consequence of the software changes.

  7. Statistical tests for person misfit in computerized adaptive testing

    NARCIS (Netherlands)

    Glas, Cornelis A.W.; Meijer, R.R.; van Krimpen-Stoop, Edith

    1998-01-01

    Recently, several person-fit statistics have been proposed to detect nonfitting response patterns. This study is designed to generalize an approach followed by Klauer (1995) to an adaptive testing system using the two-parameter logistic model (2PL) as a null model. The approach developed by Klauer

  8. Modified Distribution-Free Goodness-of-Fit Test Statistic.

    Science.gov (United States)

    Chun, So Yeon; Browne, Michael W; Shapiro, Alexander

    2018-03-01

    Covariance structure analysis and its structural equation modeling extensions have become one of the most widely used methodologies in social sciences such as psychology, education, and economics. An important issue in such analysis is to assess the goodness of fit of a model under analysis. One of the most popular test statistics used in covariance structure analysis is the asymptotically distribution-free (ADF) test statistic introduced by Browne (Br J Math Stat Psychol 37:62-83, 1984). The ADF statistic can be used to test models without any specific distribution assumption (e.g., multivariate normal distribution) of the observed data. Despite its advantage, it has been shown in various empirical studies that unless sample sizes are extremely large, this ADF statistic could perform very poorly in practice. In this paper, we provide a theoretical explanation for this phenomenon and further propose a modified test statistic that improves the performance in samples of realistic size. The proposed statistic deals with the possible ill-conditioning of the involved large-scale covariance matrices.

  9. Test for the statistical significance of differences between ROC curves

    International Nuclear Information System (INIS)

    Metz, C.E.; Kronman, H.B.

    1979-01-01

    A test for the statistical significance of observed differences between two measured Receiver Operating Characteristic (ROC) curves has been designed and evaluated. The set of observer response data for each ROC curve is assumed to be independent and to arise from a ROC curve having a form which, in the absence of statistical fluctuations in the response data, graphs as a straight line on double normal-deviate axes. To test the significance of an apparent difference between two measured ROC curves, maximum likelihood estimates of the two parameters of each curve and the associated parameter variances and covariance are calculated from the corresponding set of observer response data. An approximate Chi-square statistic with two degrees of freedom is then constructed from the differences between the parameters estimated for each ROC curve and from the variances and covariances of these estimates. This statistic is known to be truly Chi-square distributed only in the limit of large numbers of trials in the observer performance experiments. Performance of the statistic for data arising from a limited number of experimental trials was evaluated. Independent sets of rating scale data arising from the same underlying ROC curve were paired, and the fraction of differences found (falsely) significant was compared to the significance level, α, used with the test. Although test performance was found to be somewhat dependent on both the number of trials in the data and the position of the underlying ROC curve in the ROC space, the results for various significance levels showed the test to be reliable under practical experimental conditions

  10. Explorations in Statistics: Hypothesis Tests and P Values

    Science.gov (United States)

    Curran-Everett, Douglas

    2009-01-01

    Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This second installment of "Explorations in Statistics" delves into test statistics and P values, two concepts fundamental to the test of a scientific null hypothesis. The essence of a test statistic is that it compares what…

  11. Testing for Statistical Discrimination based on Gender

    DEFF Research Database (Denmark)

    Lesner, Rune Vammen

    . It is shown that the implications of both screening discrimination and stereotyping are consistent with observable wage dynamics. In addition, it is found that the gender wage gap decreases in tenure but increases in job transitions and that the fraction of women in high-ranking positions within a firm does......This paper develops a model which incorporates the two most commonly cited strands of the literature on statistical discrimination, namely screening discrimination and stereotyping. The model is used to provide empirical evidence of statistical discrimination based on gender in the labour market...... not affect the level of statistical discrimination by gender....

  12. Statistical Decision Theory Estimation, Testing, and Selection

    CERN Document Server

    Liese, Friedrich

    2008-01-01

    Suitable for advanced graduate students and researchers in mathematical statistics and decision theory, this title presents an account of the concepts and a treatment of the major results of classical finite sample size decision theory and modern asymptotic decision theory

  13. Testing for Statistical Discrimination based on Gender

    OpenAIRE

    Lesner, Rune Vammen

    2016-01-01

    This paper develops a model which incorporates the two most commonly cited strands of the literature on statistical discrimination, namely screening discrimination and stereotyping. The model is used to provide empirical evidence of statistical discrimination based on gender in the labour market. It is shown that the implications of both screening discrimination and stereotyping are consistent with observable wage dynamics. In addition, it is found that the gender wage gap decreases in tenure...

  14. Distinguish Dynamic Basic Blocks by Structural Statistical Testing

    DEFF Research Database (Denmark)

    Petit, Matthieu; Gotlieb, Arnaud

    Statistical testing aims at generating random test data that respect selected probabilistic properties. A distribution probability is associated with the program input space in order to achieve statistical test purpose: to test the most frequent usage of software or to maximize the probability of...... control flow path) during the test data selection. We implemented this algorithm in a statistical test data generator for Java programs. A first experimental validation is presented...

  15. Extending the Reach of Statistical Software Testing

    National Research Council Canada - National Science Library

    Weber, Robert

    2004-01-01

    .... In particular, as system complexity increases, the matrices required to generate test cases and perform model analysis can grow dramatically, even exponentially, overwhelming the test generation...

  16. A critique of statistical hypothesis testing in clinical research

    Directory of Open Access Journals (Sweden)

    Somik Raha

    2011-01-01

    Full Text Available Many have documented the difficulty of using the current paradigm of Randomized Controlled Trials (RCTs to test and validate the effectiveness of alternative medical systems such as Ayurveda. This paper critiques the applicability of RCTs for all clinical knowledge-seeking endeavors, of which Ayurveda research is a part. This is done by examining statistical hypothesis testing, the underlying foundation of RCTs, from a practical and philosophical perspective. In the philosophical critique, the two main worldviews of probability are that of the Bayesian and the frequentist. The frequentist worldview is a special case of the Bayesian worldview requiring the unrealistic assumptions of knowing nothing about the universe and believing that all observations are unrelated to each other. Many have claimed that the first belief is necessary for science, and this claim is debunked by comparing variations in learning with different prior beliefs. Moving beyond the Bayesian and frequentist worldviews, the notion of hypothesis testing itself is challenged on the grounds that a hypothesis is an unclear distinction, and assigning a probability on an unclear distinction is an exercise that does not lead to clarity of action. This critique is of the theory itself and not any particular application of statistical hypothesis testing. A decision-making frame is proposed as a way of both addressing this critique and transcending ideological debates on probability. An example of a Bayesian decision-making approach is shown as an alternative to statistical hypothesis testing, utilizing data from a past clinical trial that studied the effect of Aspirin on heart attacks in a sample population of doctors. As a big reason for the prevalence of RCTs in academia is legislation requiring it, the ethics of legislating the use of statistical methods for clinical research is also examined.

  17. [The research protocol VI: How to choose the appropriate statistical test. Inferential statistics].

    Science.gov (United States)

    Flores-Ruiz, Eric; Miranda-Novales, María Guadalupe; Villasís-Keever, Miguel Ángel

    2017-01-01

    The statistical analysis can be divided in two main components: descriptive analysis and inferential analysis. An inference is to elaborate conclusions from the tests performed with the data obtained from a sample of a population. Statistical tests are used in order to establish the probability that a conclusion obtained from a sample is applicable to the population from which it was obtained. However, choosing the appropriate statistical test in general poses a challenge for novice researchers. To choose the statistical test it is necessary to take into account three aspects: the research design, the number of measurements and the scale of measurement of the variables. Statistical tests are divided into two sets, parametric and nonparametric. Parametric tests can only be used if the data show a normal distribution. Choosing the right statistical test will make it easier for readers to understand and apply the results.

  18. The research protocol VI: How to choose the appropriate statistical test. Inferential statistics

    Directory of Open Access Journals (Sweden)

    Eric Flores-Ruiz

    2017-10-01

    Full Text Available The statistical analysis can be divided in two main components: descriptive analysis and inferential analysis. An inference is to elaborate conclusions from the tests performed with the data obtained from a sample of a population. Statistical tests are used in order to establish the probability that a conclusion obtained from a sample is applicable to the population from which it was obtained. However, choosing the appropriate statistical test in general poses a challenge for novice researchers. To choose the statistical test it is necessary to take into account three aspects: the research design, the number of measurements and the scale of measurement of the variables. Statistical tests are divided into two sets, parametric and nonparametric. Parametric tests can only be used if the data show a normal distribution. Choosing the right statistical test will make it easier for readers to understand and apply the results.

  19. statistical tests for frequency distribution of mean gravity anomalies

    African Journals Online (AJOL)

    ES Obe

    1980-03-01

    Mar 1, 1980 ... STATISTICAL TESTS FOR FREQUENCY DISTRIBUTION OF MEAN. GRAVITY ANOMALIES. By ... approach. Kaula [1,2] discussed the method of applying statistical techniques in the ..... mathematical foundation of physical ...

  20. Statistical Tests for Mixed Linear Models

    CERN Document Server

    Khuri, André I; Sinha, Bimal K

    2011-01-01

    An advanced discussion of linear models with mixed or random effects. In recent years a breakthrough has occurred in our ability to draw inferences from exact and optimum tests of variance component models, generating much research activity that relies on linear models with mixed and random effects. This volume covers the most important research of the past decade as well as the latest developments in hypothesis testing. It compiles all currently available results in the area of exact and optimum tests for variance component models and offers the only comprehensive treatment for these models a

  1. Bayesian models based on test statistics for multiple hypothesis testing problems.

    Science.gov (United States)

    Ji, Yuan; Lu, Yiling; Mills, Gordon B

    2008-04-01

    We propose a Bayesian method for the problem of multiple hypothesis testing that is routinely encountered in bioinformatics research, such as the differential gene expression analysis. Our algorithm is based on modeling the distributions of test statistics under both null and alternative hypotheses. We substantially reduce the complexity of the process of defining posterior model probabilities by modeling the test statistics directly instead of modeling the full data. Computationally, we apply a Bayesian FDR approach to control the number of rejections of null hypotheses. To check if our model assumptions for the test statistics are valid for various bioinformatics experiments, we also propose a simple graphical model-assessment tool. Using extensive simulations, we demonstrate the performance of our models and the utility of the model-assessment tool. In the end, we apply the proposed methodology to an siRNA screening and a gene expression experiment.

  2. Testing for statistical discrimination in health care.

    Science.gov (United States)

    Balsa, Ana I; McGuire, Thomas G; Meredith, Lisa S

    2005-02-01

    To examine the extent to which doctors' rational reactions to clinical uncertainty ("statistical discrimination") can explain racial differences in the diagnosis of depression, hypertension, and diabetes. Main data are from the Medical Outcomes Study (MOS), a 1986 study conducted by RAND Corporation in three U.S. cities. The study compares the processes and outcomes of care for patients in different health care systems. Complementary data from National Health And Examination Survey III (NHANES III) and National Comorbidity Survey (NCS) are also used. Across three systems of care (staff health maintenance organizations, multispecialty groups, and solo practices), the MOS selected 523 health care clinicians. A representative cross-section (21,480) of patients was then chosen from a pool of adults who visited any of these providers during a 9-day period. We analyzed a subsample of the MOS data consisting of patients of white family physicians or internists (11,664 patients). We obtain variables reflecting patients' health conditions and severity, demographics, socioeconomic status, and insurance from the patients' screener interview (administered by MOS staff prior to the patient's encounter with the clinician). We used the reports made by the clinician after the visit to construct indicators of doctors' diagnoses. We obtained prevalence rates from NHANES III and NCS. We find evidence consistent with statistical discrimination for diagnoses of hypertension, diabetes, and depression. In particular, we find that if clinicians act like Bayesians, plausible priors held by the physician about the prevalence of the disease across racial groups could account for racial differences in the diagnosis of hypertension and diabetes. In the case of depression, we find evidence that race affects decisions through differences in communication patterns between doctors and white and minority patients. To contend effectively with inequities in health care, it is necessary to understand

  3. CONFIDENCE LEVELS AND/VS. STATISTICAL HYPOTHESIS TESTING IN STATISTICAL ANALYSIS. CASE STUDY

    Directory of Open Access Journals (Sweden)

    ILEANA BRUDIU

    2009-05-01

    Full Text Available Estimated parameters with confidence intervals and testing statistical assumptions used in statistical analysis to obtain conclusions on research from a sample extracted from the population. Paper to the case study presented aims to highlight the importance of volume of sample taken in the study and how this reflects on the results obtained when using confidence intervals and testing for pregnant. If statistical testing hypotheses not only give an answer "yes" or "no" to some questions of statistical estimation using statistical confidence intervals provides more information than a test statistic, show high degree of uncertainty arising from small samples and findings build in the "marginally significant" or "almost significant (p very close to 0.05.

  4. A statistical procedure for testing financial contagion

    Directory of Open Access Journals (Sweden)

    Attilio Gardini

    2013-05-01

    Full Text Available The aim of the paper is to provide an analysis of contagion through the measurement of the risk premia disequilibria dynamics. In order to discriminate among several disequilibrium situations we propose to test contagion on the basis of a two-step procedure: in the first step we estimate the preference parameters of the consumption-based asset pricing model (CCAPM to control for fundamentals and to measure the equilibrium risk premia in different countries; in the second step we measure the differences among empirical risk premia and equilibrium risk premia in order to test cross-country disequilibrium situations due to contagion. Disequilibrium risk premium measures are modelled by the multivariate DCC-GARCH model including a deterministic crisis variable. The model describes simultaneously the risk premia dynamics due to endogenous amplifications of volatility and to exogenous idiosyncratic shocks (contagion, having controlled for fundamentals effects in the first step. Our approach allows us to achieve two goals: (i to identify the disequilibria generated by irrational behaviours of the agents, which cause increasing in volatility that is not explained by the economic fundamentals but is endogenous to financial markets, and (ii to assess the existence of contagion effect defined by exogenous shift in cross-country return correlations during crisis periods. Our results show evidence of contagion from the United States to United Kingdom, Japan, France, and Italy during the financial crisis which started in 2007-08.

  5. Statistical hypothesis tests of some micrometeorological observations

    International Nuclear Information System (INIS)

    SethuRaman, S.; Tichler, J.

    1977-01-01

    Chi-square goodness-of-fit is used to test the hypothesis that the medium scale of turbulence in the atmospheric surface layer is normally distributed. Coefficients of skewness and excess are computed from the data. If the data are not normal, these coefficients are used in Edgeworth's asymptotic expansion of Gram-Charlier series to determine an altrnate probability density function. The observed data are then compared with the modified probability densities and the new chi-square values computed.Seventy percent of the data analyzed was either normal or approximatley normal. The coefficient of skewness g 1 has a good correlation with the chi-square values. Events with vertical-barg 1 vertical-bar 1 vertical-bar<0.43 were approximately normal. Intermittency associated with the formation and breaking of internal gravity waves in surface-based inversions over water is thought to be the reason for the non-normality

  6. HOW TO SELECT APPROPRIATE STATISTICAL TEST IN SCIENTIFIC ARTICLES

    Directory of Open Access Journals (Sweden)

    Vladimir TRAJKOVSKI

    2016-09-01

    Full Text Available Statistics is mathematical science dealing with the collection, analysis, interpretation, and presentation of masses of numerical data in order to draw relevant conclusions. Statistics is a form of mathematical analysis that uses quantified models, representations and synopses for a given set of experimental data or real-life studies. The students and young researchers in biomedical sciences and in special education and rehabilitation often declare that they have chosen to enroll that study program because they have lack of knowledge or interest in mathematics. This is a sad statement, but there is much truth in it. The aim of this editorial is to help young researchers to select statistics or statistical techniques and statistical software appropriate for the purposes and conditions of a particular analysis. The most important statistical tests are reviewed in the article. Knowing how to choose right statistical test is an important asset and decision in the research data processing and in the writing of scientific papers. Young researchers and authors should know how to choose and how to use statistical methods. The competent researcher will need knowledge in statistical procedures. That might include an introductory statistics course, and it most certainly includes using a good statistics textbook. For this purpose, there is need to return of Statistics mandatory subject in the curriculum of the Institute of Special Education and Rehabilitation at Faculty of Philosophy in Skopje. Young researchers have a need of additional courses in statistics. They need to train themselves to use statistical software on appropriate way.

  7. Testing and qualification of confidence in statistical procedures

    Energy Technology Data Exchange (ETDEWEB)

    Serghiuta, D.; Tholammakkil, J.; Hammouda, N. [Canadian Nuclear Safety Commission (Canada); O' Hagan, A. [Sheffield Univ. (United Kingdom)

    2014-07-01

    This paper discusses a framework for designing artificial test problems, evaluation criteria, and two of the benchmark tests developed under a research project initiated by the Canadian Nuclear Safety Commission to investigate the approaches for qualification of tolerance limit methods and algorithms proposed for application in optimization of CANDU regional/neutron overpower protection trip setpoints for aged conditions. A significant component of this investigation has been the development of a series of benchmark problems of gradually increased complexity, from simple 'theoretical' problems up to complex problems closer to the real application. The first benchmark problem discussed in this paper is a simplified scalar problem which does not involve extremal, maximum or minimum, operations, typically encountered in the real applications. The second benchmark is a high dimensional, but still simple, problem for statistical inference of maximum channel power during normal operation. Bayesian algorithms have been developed for each benchmark problem to provide an independent way of constructing tolerance limits from the same data and allow assessing how well different methods make use of those data and, depending on the type of application, evaluating what the level of 'conservatism' is. The Bayesian method is not, however, used as a reference method, or 'gold' standard, but simply as an independent review method. The approach and the tests developed can be used as a starting point for developing a generic suite (generic in the sense of potentially applying whatever the proposed statistical method) of empirical studies, with clear criteria for passing those tests. Some lessons learned, in particular concerning the need to assure the completeness of the description of the application and the role of completeness of input information, are also discussed. It is concluded that a formal process which includes extended and detailed benchmark

  8. Radio resource allocation over fading channels under statistical delay constraints

    CERN Document Server

    Le-Ngoc, Tho

    2017-01-01

    This SpringerBrief presents radio resource allocation schemes for buffer-aided communications systems over fading channels under statistical delay constraints in terms of upper-bounded average delay or delay-outage probability. This Brief starts by considering a source-destination communications link with data arriving at the source transmission buffer. The first scenario, the joint optimal data admission control and power allocation problem for throughput maximization is considered, where the source is assumed to have a maximum power and an average delay constraints. The second scenario, optimal power allocation problems for energy harvesting (EH) communications systems under average delay or delay-outage constraints are explored, where the EH source harvests random amounts of energy from renewable energy sources, and stores the harvested energy in a battery during data transmission. Online resource allocation algorithms are developed when the statistical knowledge of the random channel fading, data arrivals...

  9. Testing the Difference of Correlated Agreement Coefficients for Statistical Significance

    Science.gov (United States)

    Gwet, Kilem L.

    2016-01-01

    This article addresses the problem of testing the difference between two correlated agreement coefficients for statistical significance. A number of authors have proposed methods for testing the difference between two correlated kappa coefficients, which require either the use of resampling methods or the use of advanced statistical modeling…

  10. Statistics

    CERN Document Server

    Hayslett, H T

    1991-01-01

    Statistics covers the basic principles of Statistics. The book starts by tackling the importance and the two kinds of statistics; the presentation of sample data; the definition, illustration and explanation of several measures of location; and the measures of variation. The text then discusses elementary probability, the normal distribution and the normal approximation to the binomial. Testing of statistical hypotheses and tests of hypotheses about the theoretical proportion of successes in a binomial population and about the theoretical mean of a normal population are explained. The text the

  11. Corrections of the NIST Statistical Test Suite for Randomness

    OpenAIRE

    Kim, Song-Ju; Umeno, Ken; Hasegawa, Akio

    2004-01-01

    It is well known that the NIST statistical test suite was used for the evaluation of AES candidate algorithms. We have found that the test setting of Discrete Fourier Transform test and Lempel-Ziv test of this test suite are wrong. We give four corrections of mistakes in the test settings. This suggests that re-evaluation of the test results should be needed.

  12. Asympotic efficiency of signed - rank symmetry tests under skew alternatives.

    OpenAIRE

    Alessandra Durio; Yakov Nikitin

    2002-01-01

    The efficiency of some known tests for symmetry such as the sign test, the Wilcoxon signed-rank test or more general linear signed rank tests was studied mainly under the classical alternatives of location. However it is interesting to compare the efficiencies of these tests under asymmetric alternatives like the so-called skew alternative proposed in Azzalini (1985). We find and compare local Bahadur efficiencies of linear signed-rank statistics for skew alternatives and discuss also the con...

  13. EVALUATION OF A NEW MEAN SCALED AND MOMENT ADJUSTED TEST STATISTIC FOR SEM.

    Science.gov (United States)

    Tong, Xiaoxiao; Bentler, Peter M

    2013-01-01

    Recently a new mean scaled and skewness adjusted test statistic was developed for evaluating structural equation models in small samples and with potentially nonnormal data, but this statistic has received only limited evaluation. The performance of this statistic is compared to normal theory maximum likelihood and two well-known robust test statistics. A modification to the Satorra-Bentler scaled statistic is developed for the condition that sample size is smaller than degrees of freedom. The behavior of the four test statistics is evaluated with a Monte Carlo confirmatory factor analysis study that varies seven sample sizes and three distributional conditions obtained using Headrick's fifth-order transformation to nonnormality. The new statistic performs badly in most conditions except under the normal distribution. The goodness-of-fit χ(2) test based on maximum-likelihood estimation performed well under normal distributions as well as under a condition of asymptotic robustness. The Satorra-Bentler scaled test statistic performed best overall, while the mean scaled and variance adjusted test statistic outperformed the others at small and moderate sample sizes under certain distributional conditions.

  14. Caveats for using statistical significance tests in research assessments

    DEFF Research Database (Denmark)

    Schneider, Jesper Wiborg

    2013-01-01

    controversial and numerous criticisms have been leveled against their use. Based on examples from articles by proponents of the use statistical significance tests in research assessments, we address some of the numerous problems with such tests. The issues specifically discussed are the ritual practice......This article raises concerns about the advantages of using statistical significance tests in research assessments as has recently been suggested in the debate about proper normalization procedures for citation indicators by Opthof and Leydesdorff (2010). Statistical significance tests are highly...... argue that applying statistical significance tests and mechanically adhering to their results are highly problematic and detrimental to critical thinking. We claim that the use of such tests do not provide any advantages in relation to deciding whether differences between citation indicators...

  15. Finding differentially expressed genes in high dimensional data: Rank based test statistic via a distance measure.

    Science.gov (United States)

    Mathur, Sunil; Sadana, Ajit

    2015-12-01

    We present a rank-based test statistic for the identification of differentially expressed genes using a distance measure. The proposed test statistic is highly robust against extreme values and does not assume the distribution of parent population. Simulation studies show that the proposed test is more powerful than some of the commonly used methods, such as paired t-test, Wilcoxon signed rank test, and significance analysis of microarray (SAM) under certain non-normal distributions. The asymptotic distribution of the test statistic, and the p-value function are discussed. The application of proposed method is shown using a real-life data set. © The Author(s) 2011.

  16. Statistical analysis and planning of multihundred-watt impact tests

    International Nuclear Information System (INIS)

    Martz, H.F. Jr.; Waterman, M.S.

    1977-10-01

    Modular multihundred-watt (MHW) radioisotope thermoelectric generators (RTG's) are used as a power source for spacecraft. Due to possible environmental contamination by radioactive materials, numerous tests are required to determine and verify the safety of the RTG. There are results available from 27 fueled MHW impact tests regarding hoop failure, fingerprint failure, and fuel failure. Data from the 27 tests are statistically analyzed for relationships that exist between the test design variables and the failure types. Next, these relationships are used to develop a statistical procedure for planning and conducting either future MHW impact tests or similar tests on other RTG fuel sources. Finally, some conclusions are given

  17. Planar-channeling spatial density under statistical equilibrium

    International Nuclear Information System (INIS)

    Ellison, J.A.; Picraux, S.T.

    1978-01-01

    The phase-space density for planar channeled particles has been derived for the continuum model under statistical equilibrium. This is used to obtain the particle spatial probability density as a function of incident angle. The spatial density is shown to depend on only two parameters, a normalized incident angle and a normalized planar spacing. This normalization is used to obtain, by numerical calculation, a set of universal curves for the spatial density and also for the channeled-particle wavelength as a function of amplitude. Using these universal curves, the statistical-equilibrium spatial density and the channeled-particle wavelength can be easily obtained for any case for which the continuum model can be applied. Also, a new one-parameter analytic approximation to the spatial density is developed. This parabolic approximation is shown to give excellent agreement with the exact calculations

  18. Testing Under Fire: Chicago's Problem.

    Science.gov (United States)

    Byrd, Manford, Jr.

    The history and development of city-wide testing programs in Chicago since 1936 are reviewed and placed in context with the impact on testing of Sputnik and the passage of the National Defense Education Act of 1958. Current testing problems include the time lag between events and curricular changes and new test construction, the time lag between…

  19. Two independent pivotal statistics that test location and misspecification and add-up to the Anderson-Rubin statistic

    NARCIS (Netherlands)

    Kleibergen, F.R.

    2002-01-01

    We extend the novel pivotal statistics for testing the parameters in the instrumental variables regression model. We show that these statistics result from a decomposition of the Anderson-Rubin statistic into two independent pivotal statistics. The first statistic is a score statistic that tests

  20. Kolmogorov complexity, pseudorandom generators and statistical models testing

    Czech Academy of Sciences Publication Activity Database

    Šindelář, Jan; Boček, Pavel

    2002-01-01

    Roč. 38, č. 6 (2002), s. 747-759 ISSN 0023-5954 R&D Projects: GA ČR GA102/99/1564 Institutional research plan: CEZ:AV0Z1075907 Keywords : Kolmogorov complexity * pseudorandom generators * statistical models testing Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.341, year: 2002

  1. Common pitfalls in statistical analysis: The perils of multiple testing

    Science.gov (United States)

    Ranganathan, Priya; Pramesh, C. S.; Buyse, Marc

    2016-01-01

    Multiple testing refers to situations where a dataset is subjected to statistical testing multiple times - either at multiple time-points or through multiple subgroups or for multiple end-points. This amplifies the probability of a false-positive finding. In this article, we look at the consequences of multiple testing and explore various methods to deal with this issue. PMID:27141478

  2. Significance levels for studies with correlated test statistics.

    Science.gov (United States)

    Shi, Jianxin; Levinson, Douglas F; Whittemore, Alice S

    2008-07-01

    When testing large numbers of null hypotheses, one needs to assess the evidence against the global null hypothesis that none of the hypotheses is false. Such evidence typically is based on the test statistic of the largest magnitude, whose statistical significance is evaluated by permuting the sample units to simulate its null distribution. Efron (2007) has noted that correlation among the test statistics can induce substantial interstudy variation in the shapes of their histograms, which may cause misleading tail counts. Here, we show that permutation-based estimates of the overall significance level also can be misleading when the test statistics are correlated. We propose that such estimates be conditioned on a simple measure of the spread of the observed histogram, and we provide a method for obtaining conditional significance levels. We justify this conditioning using the conditionality principle described by Cox and Hinkley (1974). Application of the method to gene expression data illustrates the circumstances when conditional significance levels are needed.

  3. Timed Testing under Partial Observability

    DEFF Research Database (Denmark)

    David, Alexandre; Larsen, Kim Guldstrand; Li, Shuhao

    2009-01-01

    observability of SUT using a set of predicates over the TGA state space, and specify the test purposes in Computation Tree Logic (CTL) formulas. A recently developed partially observable timed game solver is used to generate winning strategies, which are used as test cases. We propose a conformance testing...

  4. Comparison of Statistical Methods for Detector Testing Programs

    Energy Technology Data Exchange (ETDEWEB)

    Rennie, John Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Abhold, Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-10-14

    A typical goal for any detector testing program is to ascertain not only the performance of the detector systems under test, but also the confidence that systems accepted using that testing program’s acceptance criteria will exceed a minimum acceptable performance (which is usually expressed as the minimum acceptable success probability, p). A similar problem often arises in statistics, where we would like to ascertain the fraction, p, of a population of items that possess a property that may take one of two possible values. Typically, the problem is approached by drawing a fixed sample of size n, with the number of items out of n that possess the desired property, x, being termed successes. The sample mean gives an estimate of the population mean p ≈ x/n, although usually it is desirable to accompany such an estimate with a statement concerning the range within which p may fall and the confidence associated with that range. Procedures for establishing such ranges and confidence limits are described in detail by Clopper, Brown, and Agresti for two-sided symmetric confidence intervals.

  5. Statistical inferences for bearings life using sudden death test

    Directory of Open Access Journals (Sweden)

    Morariu Cristin-Olimpiu

    2017-01-01

    Full Text Available In this paper we propose a calculus method for reliability indicators estimation and a complete statistical inferences for three parameters Weibull distribution of bearings life. Using experimental values regarding the durability of bearings tested on stands by the sudden death tests involves a series of particularities of the estimation using maximum likelihood method and statistical inference accomplishment. The paper detailing these features and also provides an example calculation.

  6. Robust inference from multiple test statistics via permutations: a better alternative to the single test statistic approach for randomized trials.

    Science.gov (United States)

    Ganju, Jitendra; Yu, Xinxin; Ma, Guoguang Julie

    2013-01-01

    Formal inference in randomized clinical trials is based on controlling the type I error rate associated with a single pre-specified statistic. The deficiency of using just one method of analysis is that it depends on assumptions that may not be met. For robust inference, we propose pre-specifying multiple test statistics and relying on the minimum p-value for testing the null hypothesis of no treatment effect. The null hypothesis associated with the various test statistics is that the treatment groups are indistinguishable. The critical value for hypothesis testing comes from permutation distributions. Rejection of the null hypothesis when the smallest p-value is less than the critical value controls the type I error rate at its designated value. Even if one of the candidate test statistics has low power, the adverse effect on the power of the minimum p-value statistic is not much. Its use is illustrated with examples. We conclude that it is better to rely on the minimum p-value rather than a single statistic particularly when that single statistic is the logrank test, because of the cost and complexity of many survival trials. Copyright © 2013 John Wiley & Sons, Ltd.

  7. Log-concave Probability Distributions: Theory and Statistical Testing

    DEFF Research Database (Denmark)

    An, Mark Yuing

    1996-01-01

    This paper studies the broad class of log-concave probability distributions that arise in economics of uncertainty and information. For univariate, continuous, and log-concave random variables we prove useful properties without imposing the differentiability of density functions. Discrete...... and multivariate distributions are also discussed. We propose simple non-parametric testing procedures for log-concavity. The test statistics are constructed to test one of the two implicati ons of log-concavity: increasing hazard rates and new-is-better-than-used (NBU) property. The test for increasing hazard...... rates are based on normalized spacing of the sample order statistics. The tests for NBU property fall into the category of Hoeffding's U-statistics...

  8. Accelerated testing statistical models, test plans, and data analysis

    CERN Document Server

    Nelson, Wayne B

    2009-01-01

    The Wiley-Interscience Paperback Series consists of selected books that have been made more accessible to consumers in an effort to increase global appeal and general circulation. With these new unabridged softcover volumes, Wiley hopes to extend the lives of these works by making them available to future generations of statisticians, mathematicians, and scientists. "". . . a goldmine of knowledge on accelerated life testing principles and practices . . . one of the very few capable of advancing the science of reliability. It definitely belongs in every bookshelf on engineering.""-Dev G.

  9. A statistical design for testing apomictic diversification through linkage analysis.

    Science.gov (United States)

    Zeng, Yanru; Hou, Wei; Song, Shuang; Feng, Sisi; Shen, Lin; Xia, Guohua; Wu, Rongling

    2014-03-01

    The capacity of apomixis to generate maternal clones through seed reproduction has made it a useful characteristic for the fixation of heterosis in plant breeding. It has been observed that apomixis displays pronounced intra- and interspecific diversification, but the genetic mechanisms underlying this diversification remains elusive, obstructing the exploitation of this phenomenon in practical breeding programs. By capitalizing on molecular information in mapping populations, we describe and assess a statistical design that deploys linkage analysis to estimate and test the pattern and extent of apomictic differences at various levels from genotypes to species. The design is based on two reciprocal crosses between two individuals each chosen from a hermaphrodite or monoecious species. A multinomial distribution likelihood is constructed by combining marker information from two crosses. The EM algorithm is implemented to estimate the rate of apomixis and test its difference between two plant populations or species as the parents. The design is validated by computer simulation. A real data analysis of two reciprocal crosses between hickory (Carya cathayensis) and pecan (C. illinoensis) demonstrates the utilization and usefulness of the design in practice. The design provides a tool to address fundamental and applied questions related to the evolution and breeding of apomixis.

  10. Statistical Estimation of Heterogeneities: A New Frontier in Well Testing

    Science.gov (United States)

    Neuman, S. P.; Guadagnini, A.; Illman, W. A.; Riva, M.; Vesselinov, V. V.

    2001-12-01

    Well-testing methods have traditionally relied on analytical solutions of groundwater flow equations in relatively simple domains, consisting of one or at most a few units having uniform hydraulic properties. Recently, attention has been shifting toward methods and solutions that would allow one to characterize subsurface heterogeneities in greater detail. On one hand, geostatistical inverse methods are being used to assess the spatial variability of parameters, such as permeability and porosity, on the basis of multiple cross-hole pressure interference tests. On the other hand, analytical solutions are being developed to describe the mean and variance (first and second statistical moments) of flow to a well in a randomly heterogeneous medium. Geostatistical inverse interpretation of cross-hole tests yields a smoothed but detailed "tomographic" image of how parameters actually vary in three-dimensional space, together with corresponding measures of estimation uncertainty. Moment solutions may soon allow one to interpret well tests in terms of statistical parameters such as the mean and variance of log permeability, its spatial autocorrelation and statistical anisotropy. The idea of geostatistical cross-hole tomography is illustrated through pneumatic injection tests conducted in unsaturated fractured tuff at the Apache Leap Research Site near Superior, Arizona. The idea of using moment equations to interpret well-tests statistically is illustrated through a recently developed three-dimensional solution for steady state flow to a well in a bounded, randomly heterogeneous, statistically anisotropic aquifer.

  11. Your Chi-Square Test Is Statistically Significant: Now What?

    Science.gov (United States)

    Sharpe, Donald

    2015-01-01

    Applied researchers have employed chi-square tests for more than one hundred years. This paper addresses the question of how one should follow a statistically significant chi-square test result in order to determine the source of that result. Four approaches were evaluated: calculating residuals, comparing cells, ransacking, and partitioning. Data…

  12. Statistical test for the distribution of galaxies on plates

    International Nuclear Information System (INIS)

    Garcia Lambas, D.

    1985-01-01

    A statistical test for the distribution of galaxies on plates is presented. We apply the test to synthetic astronomical plates obtained by means of numerical simulation (Garcia Lambas and Sersic 1983) with three different models for the 3-dimensional distribution, comparison with an observational plate, suggest the presence of filamentary structure. (author)

  13. CUSUM-based person-fit statistics for adaptive testing

    NARCIS (Netherlands)

    van Krimpen-Stoop, Edith; Meijer, R.R.

    1999-01-01

    Item scores that do not fit an assumed item response theory model may cause the latent trait value to be estimated inaccurately. Several person-fit statistics for detecting nonfitting score patterns for paper-and-pencil tests have been proposed. In the context of computerized adaptive tests (CAT),

  14. CUSUM-based person-fit statistics for adaptive testing

    NARCIS (Netherlands)

    van Krimpen-Stoop, Edith; Meijer, R.R.

    2001-01-01

    Item scores that do not fit an assumed item response theory model may cause the latent trait value to be inaccurately estimated. Several person-fit statistics for detecting nonfitting score patterns for paper-and-pencil tests have been proposed. In the context of computerized adaptive tests (CAT),

  15. Testing Cases under Title VII.

    Science.gov (United States)

    Rothschild, Michael; Werden, Gregory J.

    This paper discusses Congressional and judicial attempts to deal with the problem of employment practices which lead to discriminatory outcomes but which may not be discriminatory in intent. The use of paper and pencil tests as standards for hiring and promotion is focused on as an example of this type of employment practice. An historical account…

  16. THE ATKINSON INDEX, THE MORAN STATISTIC, AND TESTING EXPONENTIALITY

    OpenAIRE

    Nao, Mimoto; Ricardas, Zitikis; Department of Statistics and Probability, Michigan State University; Department of Statistical and Actuarial Sciences, University of Western Ontario

    2008-01-01

    Constructing tests for exponentiality has been an active and fruitful research area, with numerous applications in engineering, biology and other sciences concerned with life-time data. In the present paper, we construct and investigate powerful tests for exponentiality based on two well known quantities: the Atkinson index and the Moran statistic. We provide an extensive study of the performance of the tests and compare them with those already available in the literature.

  17. [Clinical research IV. Relevancy of the statistical test chosen].

    Science.gov (United States)

    Talavera, Juan O; Rivas-Ruiz, Rodolfo

    2011-01-01

    When we look at the difference between two therapies or the association of a risk factor or prognostic indicator with its outcome, we need to evaluate the accuracy of the result. This assessment is based on a judgment that uses information about the study design and statistical management of the information. This paper specifically mentions the relevance of the statistical test selected. Statistical tests are chosen mainly from two characteristics: the objective of the study and type of variables. The objective can be divided into three test groups: a) those in which you want to show differences between groups or inside a group before and after a maneuver, b) those that seek to show the relationship (correlation) between variables, and c) those that aim to predict an outcome. The types of variables are divided in two: quantitative (continuous and discontinuous) and qualitative (ordinal and dichotomous). For example, if we seek to demonstrate differences in age (quantitative variable) among patients with systemic lupus erythematosus (SLE) with and without neurological disease (two groups), the appropriate test is the "Student t test for independent samples." But if the comparison is about the frequency of females (binomial variable), then the appropriate statistical test is the χ(2).

  18. 688,112 statistical results : Content mining psychology articles for statistical test results

    NARCIS (Netherlands)

    Hartgerink, C.H.J.

    2016-01-01

    In this data deposit, I describe a dataset that is the result of content mining 167,318 published articles for statistical test results reported according to the standards prescribed by the American Psychological Association (APA). Articles published by the APA, Springer, Sage, and Taylor & Francis

  19. A Third Moment Adjusted Test Statistic for Small Sample Factor Analysis.

    Science.gov (United States)

    Lin, Johnny; Bentler, Peter M

    2012-01-01

    Goodness of fit testing in factor analysis is based on the assumption that the test statistic is asymptotically chi-square; but this property may not hold in small samples even when the factors and errors are normally distributed in the population. Robust methods such as Browne's asymptotically distribution-free method and Satorra Bentler's mean scaling statistic were developed under the presumption of non-normality in the factors and errors. This paper finds new application to the case where factors and errors are normally distributed in the population but the skewness of the obtained test statistic is still high due to sampling error in the observed indicators. An extension of Satorra Bentler's statistic is proposed that not only scales the mean but also adjusts the degrees of freedom based on the skewness of the obtained test statistic in order to improve its robustness under small samples. A simple simulation study shows that this third moment adjusted statistic asymptotically performs on par with previously proposed methods, and at a very small sample size offers superior Type I error rates under a properly specified model. Data from Mardia, Kent and Bibby's study of students tested for their ability in five content areas that were either open or closed book were used to illustrate the real-world performance of this statistic.

  20. Test Statistics and Confidence Intervals to Establish Noninferiority between Treatments with Ordinal Categorical Data.

    Science.gov (United States)

    Zhang, Fanghong; Miyaoka, Etsuo; Huang, Fuping; Tanaka, Yutaka

    2015-01-01

    The problem for establishing noninferiority is discussed between a new treatment and a standard (control) treatment with ordinal categorical data. A measure of treatment effect is used and a method of specifying noninferiority margin for the measure is provided. Two Z-type test statistics are proposed where the estimation of variance is constructed under the shifted null hypothesis using U-statistics. Furthermore, the confidence interval and the sample size formula are given based on the proposed test statistics. The proposed procedure is applied to a dataset from a clinical trial. A simulation study is conducted to compare the performance of the proposed test statistics with that of the existing ones, and the results show that the proposed test statistics are better in terms of the deviation from nominal level and the power.

  1. The MAX Statistic is Less Powerful for Genome Wide Association Studies Under Most Alternative Hypotheses.

    Science.gov (United States)

    Shifflett, Benjamin; Huang, Rong; Edland, Steven D

    2017-01-01

    Genotypic association studies are prone to inflated type I error rates if multiple hypothesis testing is performed, e.g., sequentially testing for recessive, multiplicative, and dominant risk. Alternatives to multiple hypothesis testing include the model independent genotypic χ 2 test, the efficiency robust MAX statistic, which corrects for multiple comparisons but with some loss of power, or a single Armitage test for multiplicative trend, which has optimal power when the multiplicative model holds but with some loss of power when dominant or recessive models underlie the genetic association. We used Monte Carlo simulations to describe the relative performance of these three approaches under a range of scenarios. All three approaches maintained their nominal type I error rates. The genotypic χ 2 and MAX statistics were more powerful when testing a strictly recessive genetic effect or when testing a dominant effect when the allele frequency was high. The Armitage test for multiplicative trend was most powerful for the broad range of scenarios where heterozygote risk is intermediate between recessive and dominant risk. Moreover, all tests had limited power to detect recessive genetic risk unless the sample size was large, and conversely all tests were relatively well powered to detect dominant risk. Taken together, these results suggest the general utility of the multiplicative trend test when the underlying genetic model is unknown.

  2. Reliability Evaluation of Concentric Butterfly Valve Using Statistical Hypothesis Test

    International Nuclear Information System (INIS)

    Chang, Mu Seong; Choi, Jong Sik; Choi, Byung Oh; Kim, Do Sik

    2015-01-01

    A butterfly valve is a type of flow-control device typically used to regulate a fluid flow. This paper presents an estimation of the shape parameter of the Weibull distribution, characteristic life, and B10 life for a concentric butterfly valve based on a statistical analysis of the reliability test data taken before and after the valve improvement. The difference in the shape and scale parameters between the existing and improved valves is reviewed using a statistical hypothesis test. The test results indicate that the shape parameter of the improved valve is similar to that of the existing valve, and that the scale parameter of the improved valve is found to have increased. These analysis results are particularly useful for a reliability qualification test and the determination of the service life cycles

  3. Reliability Evaluation of Concentric Butterfly Valve Using Statistical Hypothesis Test

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Mu Seong; Choi, Jong Sik; Choi, Byung Oh; Kim, Do Sik [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2015-12-15

    A butterfly valve is a type of flow-control device typically used to regulate a fluid flow. This paper presents an estimation of the shape parameter of the Weibull distribution, characteristic life, and B10 life for a concentric butterfly valve based on a statistical analysis of the reliability test data taken before and after the valve improvement. The difference in the shape and scale parameters between the existing and improved valves is reviewed using a statistical hypothesis test. The test results indicate that the shape parameter of the improved valve is similar to that of the existing valve, and that the scale parameter of the improved valve is found to have increased. These analysis results are particularly useful for a reliability qualification test and the determination of the service life cycles.

  4. Testing the statistical compatibility of independent data sets

    International Nuclear Information System (INIS)

    Maltoni, M.; Schwetz, T.

    2003-01-01

    We discuss a goodness-of-fit method which tests the compatibility between statistically independent data sets. The method gives sensible results even in cases where the χ 2 minima of the individual data sets are very low or when several parameters are fitted to a large number of data points. In particular, it avoids the problem that a possible disagreement between data sets becomes diluted by data points which are insensitive to the crucial parameters. A formal derivation of the probability distribution function for the proposed test statistics is given, based on standard theorems of statistics. The application of the method is illustrated on data from neutrino oscillation experiments, and its complementarity to the standard goodness-of-fit is discussed

  5. A comparison of test statistics for the recovery of rapid growth-based enumeration tests

    NARCIS (Netherlands)

    van den Heuvel, Edwin R.; IJzerman-Boon, Pieta C.

    This paper considers five test statistics for comparing the recovery of a rapid growth-based enumeration test with respect to the compendial microbiological method using a specific nonserial dilution experiment. The finite sample distributions of these test statistics are unknown, because they are

  6. Statistical approach for collaborative tests, reference material certification procedures

    International Nuclear Information System (INIS)

    Fangmeyer, H.; Haemers, L.; Larisse, J.

    1977-01-01

    The first part introduces the different aspects in organizing and executing intercomparison tests of chemical or physical quantities. It follows a description of a statistical procedure to handle the data collected in a circular analysis. Finally, an example demonstrates how the tool can be applied and which conclusion can be drawn of the results obtained

  7. Use of run statistics to validate tensile tests

    International Nuclear Information System (INIS)

    Eatherly, W.P.

    1981-01-01

    In tensile testing of irradiated graphites, it is difficult to assure alignment of sample and train for tensile measurements. By recording location of fractures, run (sequential) statistics can readily detect lack of randomness. The technique is based on partitioning binomial distributions

  8. Conducting tests for statistically significant differences using forest inventory data

    Science.gov (United States)

    James A. Westfall; Scott A. Pugh; John W. Coulston

    2013-01-01

    Many forest inventory and monitoring programs are based on a sample of ground plots from which estimates of forest resources are derived. In addition to evaluating metrics such as number of trees or amount of cubic wood volume, it is often desirable to make comparisons between resource attributes. To properly conduct statistical tests for differences, it is imperative...

  9. A Note on Three Statistical Tests in the Logistic Regression DIF Procedure

    Science.gov (United States)

    Paek, Insu

    2012-01-01

    Although logistic regression became one of the well-known methods in detecting differential item functioning (DIF), its three statistical tests, the Wald, likelihood ratio (LR), and score tests, which are readily available under the maximum likelihood, do not seem to be consistently distinguished in DIF literature. This paper provides a clarifying…

  10. Using the Bootstrap Method for a Statistical Significance Test of Differences between Summary Histograms

    Science.gov (United States)

    Xu, Kuan-Man

    2006-01-01

    A new method is proposed to compare statistical differences between summary histograms, which are the histograms summed over a large ensemble of individual histograms. It consists of choosing a distance statistic for measuring the difference between summary histograms and using a bootstrap procedure to calculate the statistical significance level. Bootstrapping is an approach to statistical inference that makes few assumptions about the underlying probability distribution that describes the data. Three distance statistics are compared in this study. They are the Euclidean distance, the Jeffries-Matusita distance and the Kuiper distance. The data used in testing the bootstrap method are satellite measurements of cloud systems called cloud objects. Each cloud object is defined as a contiguous region/patch composed of individual footprints or fields of view. A histogram of measured values over footprints is generated for each parameter of each cloud object and then summary histograms are accumulated over all individual histograms in a given cloud-object size category. The results of statistical hypothesis tests using all three distances as test statistics are generally similar, indicating the validity of the proposed method. The Euclidean distance is determined to be most suitable after comparing the statistical tests of several parameters with distinct probability distributions among three cloud-object size categories. Impacts on the statistical significance levels resulting from differences in the total lengths of satellite footprint data between two size categories are also discussed.

  11. 688,112 statistical results: Content mining psychology articles for statistical test results

    OpenAIRE

    Hartgerink, C.H.J.

    2016-01-01

    In this data deposit, I describe a dataset that is the result of content mining 167,318 published articles for statistical test results reported according to the standards prescribed by the American Psychological Association (APA). Articles published by the APA, Springer, Sage, and Taylor & Francis were included (mining from Wiley and Elsevier was actively blocked). As a result of this content mining, 688,112 results from 50,845 articles were extracted. In order to provide a comprehensive set...

  12. Testing statistical isotropy in cosmic microwave background polarization maps

    Science.gov (United States)

    Rath, Pranati K.; Samal, Pramoda Kumar; Panda, Srikanta; Mishra, Debesh D.; Aluri, Pavan K.

    2018-04-01

    We apply our symmetry based Power tensor technique to test conformity of PLANCK Polarization maps with statistical isotropy. On a wide range of angular scales (l = 40 - 150), our preliminary analysis detects many statistically anisotropic multipoles in foreground cleaned full sky PLANCK polarization maps viz., COMMANDER and NILC. We also study the effect of residual foregrounds that may still be present in the Galactic plane using both common UPB77 polarization mask, as well as the individual component separation method specific polarization masks. However, some of the statistically anisotropic modes still persist, albeit significantly in NILC map. We further probed the data for any coherent alignments across multipoles in several bins from the chosen multipole range.

  13. Statistical analysis of lightning electric field measured under Malaysian condition

    Science.gov (United States)

    Salimi, Behnam; Mehranzamir, Kamyar; Abdul-Malek, Zulkurnain

    2014-02-01

    Lightning is an electrical discharge during thunderstorms that can be either within clouds (Inter-Cloud), or between clouds and ground (Cloud-Ground). The Lightning characteristics and their statistical information are the foundation for the design of lightning protection system as well as for the calculation of lightning radiated fields. Nowadays, there are various techniques to detect lightning signals and to determine various parameters produced by a lightning flash. Each technique provides its own claimed performances. In this paper, the characteristics of captured broadband electric fields generated by cloud-to-ground lightning discharges in South of Malaysia are analyzed. A total of 130 cloud-to-ground lightning flashes from 3 separate thunderstorm events (each event lasts for about 4-5 hours) were examined. Statistical analyses of the following signal parameters were presented: preliminary breakdown pulse train time duration, time interval between preliminary breakdowns and return stroke, multiplicity of stroke, and percentages of single stroke only. The BIL model is also introduced to characterize the lightning signature patterns. Observations on the statistical analyses show that about 79% of lightning signals fit well with the BIL model. The maximum and minimum of preliminary breakdown time duration of the observed lightning signals are 84 ms and 560 us, respectively. The findings of the statistical results show that 7.6% of the flashes were single stroke flashes, and the maximum number of strokes recorded was 14 multiple strokes per flash. A preliminary breakdown signature in more than 95% of the flashes can be identified.

  14. Statistical complexity without explicit reference to underlying probabilities

    Science.gov (United States)

    Pennini, F.; Plastino, A.

    2018-06-01

    We show that extremely simple systems of a not too large number of particles can be simultaneously thermally stable and complex. To such an end, we extend the statistical complexity's notion to simple configurations of non-interacting particles, without appeal to probabilities, and discuss configurational properties.

  15. Cointegration rank testing under conditional heteroskedasticity

    DEFF Research Database (Denmark)

    Cavaliere, Giuseppe; Rahbek, Anders Christian; Taylor, Robert M.

    2010-01-01

    We analyze the properties of the conventional Gaussian-based cointegrating rank tests of Johansen (1996, Likelihood-Based Inference in Cointegrated Vector Autoregressive Models) in the case where the vector of series under test is driven by globally stationary, conditionally heteroskedastic......, relative to tests based on the asymptotic critical values or the i.i.d. bootstrap, the wild bootstrap rank tests perform very well in small samples under a variety of conditionally heteroskedastic innovation processes. An empirical application to the term structure of interest rates is given....

  16. A statistical test for outlier identification in data envelopment analysis

    Directory of Open Access Journals (Sweden)

    Morteza Khodabin

    2010-09-01

    Full Text Available In the use of peer group data to assess individual, typical or best practice performance, the effective detection of outliers is critical for achieving useful results. In these ‘‘deterministic’’ frontier models, statistical theory is now mostly available. This paper deals with the statistical pared sample method and its capability of detecting outliers in data envelopment analysis. In the presented method, each observation is deleted from the sample once and the resulting linear program is solved, leading to a distribution of efficiency estimates. Based on the achieved distribution, a pared test is designed to identify the potential outlier(s. We illustrate the method through a real data set. The method could be used in a first step, as an exploratory data analysis, before using any frontier estimation.

  17. Statistical testing of association between menstruation and migraine.

    Science.gov (United States)

    Barra, Mathias; Dahl, Fredrik A; Vetvik, Kjersti G

    2015-02-01

    To repair and refine a previously proposed method for statistical analysis of association between migraine and menstruation. Menstrually related migraine (MRM) affects about 20% of female migraineurs in the general population. The exact pathophysiological link from menstruation to migraine is hypothesized to be through fluctuations in female reproductive hormones, but the exact mechanisms remain unknown. Therefore, the main diagnostic criterion today is concurrency of migraine attacks with menstruation. Methods aiming to exclude spurious associations are wanted, so that further research into these mechanisms can be performed on a population with a true association. The statistical method is based on a simple two-parameter null model of MRM (which allows for simulation modeling), and Fisher's exact test (with mid-p correction) applied to standard 2 × 2 contingency tables derived from the patients' headache diaries. Our method is a corrected version of a previously published flawed framework. To our best knowledge, no other published methods for establishing a menstruation-migraine association by statistical means exist today. The probabilistic methodology shows good performance when subjected to receiver operator characteristic curve analysis. Quick reference cutoff values for the clinical setting were tabulated for assessing association given a patient's headache history. In this paper, we correct a proposed method for establishing association between menstruation and migraine by statistical methods. We conclude that the proposed standard of 3-cycle observations prior to setting an MRM diagnosis should be extended with at least one perimenstrual window to obtain sufficient information for statistical processing. © 2014 American Headache Society.

  18. Quantum Statistical Testing of a Quantum Random Number Generator

    Energy Technology Data Exchange (ETDEWEB)

    Humble, Travis S [ORNL

    2014-01-01

    The unobservable elements in a quantum technology, e.g., the quantum state, complicate system verification against promised behavior. Using model-based system engineering, we present methods for verifying the opera- tion of a prototypical quantum random number generator. We begin with the algorithmic design of the QRNG followed by the synthesis of its physical design requirements. We next discuss how quantum statistical testing can be used to verify device behavior as well as detect device bias. We conclude by highlighting how system design and verification methods must influence effort to certify future quantum technologies.

  19. Evaluation of the Wishart test statistics for polarimetric SAR data

    DEFF Research Database (Denmark)

    Skriver, Henning; Nielsen, Allan Aasbjerg; Conradsen, Knut

    2003-01-01

    A test statistic for equality of two covariance matrices following the complex Wishart distribution has previously been used in new algorithms for change detection, edge detection and segmentation in polarimetric SAR images. Previously, the results for change detection and edge detection have been...... quantitatively evaluated. This paper deals with the evaluation of segmentation. A segmentation performance measure originally developed for single-channel SAR images has been extended to polarimetric SAR images, and used to evaluate segmentation for a merge-using-moment algorithm for polarimetric SAR data....

  20. Development of modelling algorithm of technological systems by statistical tests

    Science.gov (United States)

    Shemshura, E. A.; Otrokov, A. V.; Chernyh, V. G.

    2018-03-01

    The paper tackles the problem of economic assessment of design efficiency regarding various technological systems at the stage of their operation. The modelling algorithm of a technological system was performed using statistical tests and with account of the reliability index allows estimating the level of machinery technical excellence and defining the efficiency of design reliability against its performance. Economic feasibility of its application shall be determined on the basis of service quality of a technological system with further forecasting of volumes and the range of spare parts supply.

  1. Reliability assessment for safety critical systems by statistical random testing

    International Nuclear Information System (INIS)

    Mills, S.E.

    1995-11-01

    In this report we present an overview of reliability assessment for software and focus on some basic aspects of assessing reliability for safety critical systems by statistical random testing. We also discuss possible deviations from some essential assumptions on which the general methodology is based. These deviations appear quite likely in practical applications. We present and discuss possible remedies and adjustments and then undertake applying this methodology to a portion of the SDS1 software. We also indicate shortcomings of the methodology and possible avenues to address to follow to address these problems. (author). 128 refs., 11 tabs., 31 figs

  2. Reliability assessment for safety critical systems by statistical random testing

    Energy Technology Data Exchange (ETDEWEB)

    Mills, S E [Carleton Univ., Ottawa, ON (Canada). Statistical Consulting Centre

    1995-11-01

    In this report we present an overview of reliability assessment for software and focus on some basic aspects of assessing reliability for safety critical systems by statistical random testing. We also discuss possible deviations from some essential assumptions on which the general methodology is based. These deviations appear quite likely in practical applications. We present and discuss possible remedies and adjustments and then undertake applying this methodology to a portion of the SDS1 software. We also indicate shortcomings of the methodology and possible avenues to address to follow to address these problems. (author). 128 refs., 11 tabs., 31 figs.

  3. Statistical characteristics of mechanical heart valve cavitation in accelerated testing.

    Science.gov (United States)

    Wu, Changfu; Hwang, Ned H C; Lin, Yu-Kweng M

    2004-07-01

    Cavitation damage has been observed on mechanical heart valves (MHVs) undergoing accelerated testing. Cavitation itself can be modeled as a stochastic process, as it varies from beat to beat of the testing machine. This in-vitro study was undertaken to investigate the statistical characteristics of MHV cavitation. A 25-mm St. Jude Medical bileaflet MHV (SJM 25) was tested in an accelerated tester at various pulse rates, ranging from 300 to 1,000 bpm, with stepwise increments of 100 bpm. A miniature pressure transducer was placed near a leaflet tip on the inflow side of the valve, to monitor regional transient pressure fluctuations at instants of valve closure. The pressure trace associated with each beat was passed through a 70 kHz high-pass digital filter to extract the high-frequency oscillation (HFO) components resulting from the collapse of cavitation bubbles. Three intensity-related measures were calculated for each HFO burst: its time span; its local root-mean-square (LRMS) value; and the area enveloped by the absolute value of the HFO pressure trace and the time axis, referred to as cavitation impulse. These were treated as stochastic processes, of which the first-order probability density functions (PDFs) were estimated for each test rate. Both the LRMS value and cavitation impulse were log-normal distributed, and the time span was normal distributed. These distribution laws were consistent at different test rates. The present investigation was directed at understanding MHV cavitation as a stochastic process. The results provide a basis for establishing further the statistical relationship between cavitation intensity and time-evolving cavitation damage on MHV surfaces. These data are required to assess and compare the performance of MHVs of different designs.

  4. Statistical tests for power-law cross-correlated processes

    Science.gov (United States)

    Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

    2011-12-01

    For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ρDCCA(T,n), where T is the total length of the time series and n the window size. For ρDCCA(T,n), we numerically calculated the Cauchy inequality -1≤ρDCCA(T,n)≤1. Here we derive -1≤ρDCCA(T,n)≤1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρDCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ρDCCA(T,n) tends with increasing T to 1/T. Using ρDCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

  5. A study of statistical tests for near-real-time materials accountancy using field test data of Tokai reprocessing plant

    International Nuclear Information System (INIS)

    Ihara, Hitoshi; Nishimura, Hideo; Ikawa, Koji; Miura, Nobuyuki; Iwanaga, Masayuki; Kusano, Toshitsugu.

    1988-03-01

    An Near-Real-Time Materials Accountancy(NRTA) system had been developed as an advanced safeguards measure for PNC Tokai Reprocessing Plant; a minicomputer system for NRTA data processing was designed and constructed. A full scale field test was carried out as a JASPAS(Japan Support Program for Agency Safeguards) project with the Agency's participation and the NRTA data processing system was used. Using this field test data, investigation of the detection power of a statistical test under real circumstances was carried out for five statistical tests, i.e., a significance test of MUF, CUMUF test, average loss test, MUF residual test and Page's test on MUF residuals. The result shows that the CUMUF test, average loss test, MUF residual test and the Page's test on MUF residual test are useful to detect a significant loss or diversion. An unmeasured inventory estimation model for the PNC reprocessing plant was developed in this study. Using this model, the field test data from the C-1 to 85 - 2 campaigns were re-analyzed. (author)

  6. Statistics of software vulnerability detection in certification testing

    Science.gov (United States)

    Barabanov, A. V.; Markov, A. S.; Tsirlov, V. L.

    2018-05-01

    The paper discusses practical aspects of introduction of the methods to detect software vulnerability in the day-to-day activities of the accredited testing laboratory. It presents the approval results of the vulnerability detection methods as part of the study of the open source software and the software that is a test object of the certification tests under information security requirements, including software for communication networks. Results of the study showing the allocation of identified vulnerabilities by types of attacks, country of origin, programming languages used in the development, methods for detecting vulnerability, etc. are given. The experience of foreign information security certification systems related to the detection of certified software vulnerabilities is analyzed. The main conclusion based on the study is the need to implement practices for developing secure software in the development life cycle processes. The conclusions and recommendations for the testing laboratories on the implementation of the vulnerability analysis methods are laid down.

  7. Why the null matters: statistical tests, random walks and evolution.

    Science.gov (United States)

    Sheets, H D; Mitchell, C E

    2001-01-01

    A number of statistical tests have been developed to determine what type of dynamics underlie observed changes in morphology in evolutionary time series, based on the pattern of change within the time series. The theory of the 'scaled maximum', the 'log-rate-interval' (LRI) method, and the Hurst exponent all operate on the same principle of comparing the maximum change, or rate of change, in the observed dataset to the maximum change expected of a random walk. Less change in a dataset than expected of a random walk has been interpreted as indicating stabilizing selection, while more change implies directional selection. The 'runs test' in contrast, operates on the sequencing of steps, rather than on excursion. Applications of these tests to computer generated, simulated time series of known dynamical form and various levels of additive noise indicate that there is a fundamental asymmetry in the rate of type II errors of the tests based on excursion: they are all highly sensitive to noise in models of directional selection that result in a linear trend within a time series, but are largely noise immune in the case of a simple model of stabilizing selection. Additionally, the LRI method has a lower sensitivity than originally claimed, due to the large range of LRI rates produced by random walks. Examination of the published results of these tests show that they have seldom produced a conclusion that an observed evolutionary time series was due to directional selection, a result which needs closer examination in light of the asymmetric response of these tests.

  8. Accelerated Testing with Multiple Failure Modes under Several Temperature Conditions

    Directory of Open Access Journals (Sweden)

    Zongyue Yu

    2014-01-01

    Full Text Available A complicated device may have multiple failure modes, and some of the failure modes are sensitive to low temperatures. To assess the reliability of a product with multiple failure modes, this paper presents an accelerated testing in which both of the high temperatures and the low temperatures are applied. Firstly, an acceleration model based on the Arrhenius model but accounting for the influence of both the high temperatures and low temperatures is proposed. Accordingly, an accelerated testing plan including both the high temperatures and low temperatures is designed, and a statistical analysis method is developed. The reliability function of the product with multiple failure modes under variable working conditions is given by the proposed statistical analysis method. Finally, a numerical example is studied to illustrate the proposed accelerated testing. The results show that the proposed accelerated testing is rather efficient.

  9. Thermal Analysis of Bending Under Tension Test

    DEFF Research Database (Denmark)

    Ceron, Ermanno; Martins, Paulo A.F.; Bay, Niels

    2014-01-01

    during testing is similar to the one in the production tool. A universal sheet tribo-tester has been developed, which can run multiple tests automatically from coil. This allows emulating the temperature increase as in production. The present work performs finite element analysis of the evolution......The tribological conditions in deep drawing can be simulated in the Bending Under Tension test to evaluate the performance of new lubricants, tool materials, etc. Deep drawing production with automatic handling runs normally at high rate. This implies considerable heating of the tools, which...... sometimes can cause lubricant film breakdown and galling. In order to replicate the production conditions in bending under tension testing it is thus important to control the tool/workpiece interface temperature. This can be done by pre-heating the tool, but it is essential that the interface temperature...

  10. Transfer of drug dissolution testing by statistical approaches: Case study

    Science.gov (United States)

    AL-Kamarany, Mohammed Amood; EL Karbane, Miloud; Ridouan, Khadija; Alanazi, Fars K.; Hubert, Philippe; Cherrah, Yahia; Bouklouze, Abdelaziz

    2011-01-01

    The analytical transfer is a complete process that consists in transferring an analytical procedure from a sending laboratory to a receiving laboratory. After having experimentally demonstrated that also masters the procedure in order to avoid problems in the future. Method of transfers is now commonplace during the life cycle of analytical method in the pharmaceutical industry. No official guideline exists for a transfer methodology in pharmaceutical analysis and the regulatory word of transfer is more ambiguous than for validation. Therefore, in this study, Gauge repeatability and reproducibility (R&R) studies associated with other multivariate statistics appropriates were successfully applied for the transfer of the dissolution test of diclofenac sodium as a case study from a sending laboratory A (accredited laboratory) to a receiving laboratory B. The HPLC method for the determination of the percent release of diclofenac sodium in solid pharmaceutical forms (one is the discovered product and another generic) was validated using accuracy profile (total error) in the sender laboratory A. The results showed that the receiver laboratory B masters the test dissolution process, using the same HPLC analytical procedure developed in laboratory A. In conclusion, if the sender used the total error to validate its analytical method, dissolution test can be successfully transferred without mastering the analytical method validation by receiving laboratory B and the pharmaceutical analysis method state should be maintained to ensure the same reliable results in the receiving laboratory. PMID:24109204

  11. Reliability Verification of DBE Environment Simulation Test Facility by using Statistics Method

    International Nuclear Information System (INIS)

    Jang, Kyung Nam; Kim, Jong Soeg; Jeong, Sun Chul; Kyung Heum

    2011-01-01

    In the nuclear power plant, all the safety-related equipment including cables under the harsh environment should perform the equipment qualification (EQ) according to the IEEE std 323. There are three types of qualification methods including type testing, operating experience and analysis. In order to environmentally qualify the safety-related equipment using type testing method, not analysis or operation experience method, the representative sample of equipment, including interfaces, should be subjected to a series of tests. Among these tests, Design Basis Events (DBE) environment simulating test is the most important test. DBE simulation test is performed in DBE simulation test chamber according to the postulated DBE conditions including specified high-energy line break (HELB), loss of coolant accident (LOCA), main steam line break (MSLB) and etc, after thermal and radiation aging. Because most DBE conditions have 100% humidity condition, in order to trace temperature and pressure of DBE condition, high temperature steam should be used. During DBE simulation test, if high temperature steam under high pressure inject to the DBE test chamber, the temperature and pressure in test chamber rapidly increase over the target temperature. Therefore, the temperature and pressure in test chamber continue fluctuating during the DBE simulation test to meet target temperature and pressure. We should ensure fairness and accuracy of test result by confirming the performance of DBE environment simulation test facility. In this paper, in order to verify reliability of DBE environment simulation test facility, statistics method is used

  12. Nuclides migration tests under deep geological conditions

    International Nuclear Information System (INIS)

    Kumata, M.; Vandergraaf, T.T.

    1991-01-01

    Migration behaviour of technetium and iodine under deep geological conditions was investigated by performing column tests under in-situ conditions at the 240 m level of the Underground Research Laboratory (URL) constructed in a granitic batholith near Pinawa, Manitoba, Canada. 131 I was injected with tritiated water into the column. Tritium and 131 I were eluted simultaneously. Almost 100 % of injected 131 I was recovered in the tritium breakthrough region, indicating that iodine moved through the column almost without retardation under experimental conditions. On the other hand, the injected technetium with tritium was strongly retarded in the column even though the groundwater was mildly reducing. Only about 7 % of injected 95m Tc was recovered in the tritium breakthrough region and the remaining fraction was strongly sorbed on the dark mafic minerals of column materials. This strong sorption of technetium on the column materials had not been expected from the results obtained from batch experiments carried out under anaerobic conditions. (author)

  13. Effect of non-normality on test statistics for one-way independent groups designs.

    Science.gov (United States)

    Cribbie, Robert A; Fiksenbaum, Lisa; Keselman, H J; Wilcox, Rand R

    2012-02-01

    The data obtained from one-way independent groups designs is typically non-normal in form and rarely equally variable across treatment populations (i.e., population variances are heterogeneous). Consequently, the classical test statistic that is used to assess statistical significance (i.e., the analysis of variance F test) typically provides invalid results (e.g., too many Type I errors, reduced power). For this reason, there has been considerable interest in finding a test statistic that is appropriate under conditions of non-normality and variance heterogeneity. Previously recommended procedures for analysing such data include the James test, the Welch test applied either to the usual least squares estimators of central tendency and variability, or the Welch test with robust estimators (i.e., trimmed means and Winsorized variances). A new statistic proposed by Krishnamoorthy, Lu, and Mathew, intended to deal with heterogeneous variances, though not non-normality, uses a parametric bootstrap procedure. In their investigation of the parametric bootstrap test, the authors examined its operating characteristics under limited conditions and did not compare it to the Welch test based on robust estimators. Thus, we investigated how the parametric bootstrap procedure and a modified parametric bootstrap procedure based on trimmed means perform relative to previously recommended procedures when data are non-normal and heterogeneous. The results indicated that the tests based on trimmed means offer the best Type I error control and power when variances are unequal and at least some of the distribution shapes are non-normal. © 2011 The British Psychological Society.

  14. To test photon statistics by atomic beam deflection

    International Nuclear Information System (INIS)

    Wang Yuzhu; Chen Yudan; Huang Weigang; Liu Liang

    1985-02-01

    There exists a simple relation between the photon statistics in resonance fluorescence and the statistics of the momentum transferred to an atom by a plane travelling wave [Cook, R.J., Opt. Commun., 35, 347(1980)]. Using an atomic beam deflection by light pressure, we have observed sub-Poissonian statistics in resonance fluorescence of two-level atoms. (author)

  15. Development and testing of improved statistical wind power forecasting methods.

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, J.; Bessa, R.J.; Keko, H.; Sumaili, J.; Miranda, V.; Ferreira, C.; Gama, J.; Botterud, A.; Zhou, Z.; Wang, J. (Decision and Information Sciences); (INESC Porto)

    2011-12-06

    Wind power forecasting (WPF) provides important inputs to power system operators and electricity market participants. It is therefore not surprising that WPF has attracted increasing interest within the electric power industry. In this report, we document our research on improving statistical WPF algorithms for point, uncertainty, and ramp forecasting. Below, we provide a brief introduction to the research presented in the following chapters. For a detailed overview of the state-of-the-art in wind power forecasting, we refer to [1]. Our related work on the application of WPF in operational decisions is documented in [2]. Point forecasts of wind power are highly dependent on the training criteria used in the statistical algorithms that are used to convert weather forecasts and observational data to a power forecast. In Chapter 2, we explore the application of information theoretic learning (ITL) as opposed to the classical minimum square error (MSE) criterion for point forecasting. In contrast to the MSE criterion, ITL criteria do not assume a Gaussian distribution of the forecasting errors. We investigate to what extent ITL criteria yield better results. In addition, we analyze time-adaptive training algorithms and how they enable WPF algorithms to cope with non-stationary data and, thus, to adapt to new situations without requiring additional offline training of the model. We test the new point forecasting algorithms on two wind farms located in the U.S. Midwest. Although there have been advancements in deterministic WPF, a single-valued forecast cannot provide information on the dispersion of observations around the predicted value. We argue that it is essential to generate, together with (or as an alternative to) point forecasts, a representation of the wind power uncertainty. Wind power uncertainty representation can take the form of probabilistic forecasts (e.g., probability density function, quantiles), risk indices (e.g., prediction risk index) or scenarios

  16. A critical discussion of null hypothesis significance testing and statistical power analysis within psychological research

    DEFF Research Database (Denmark)

    Jones, Allan; Sommerlund, Bo

    2007-01-01

    The uses of null hypothesis significance testing (NHST) and statistical power analysis within psychological research are critically discussed. The article looks at the problems of relying solely on NHST when dealing with small and large sample sizes. The use of power-analysis in estimating...... the potential error introduced by small and large samples is advocated. Power analysis is not recommended as a replacement to NHST but as an additional source of information about the phenomena under investigation. Moreover, the importance of conceptual analysis in relation to statistical analysis of hypothesis...

  17. A statistical test for the habitable zone concept

    Science.gov (United States)

    Checlair, J.; Abbot, D. S.

    2017-12-01

    Traditional habitable zone theory assumes that the silicate-weathering feedback regulates the atmospheric CO2 of planets within the habitable zone to maintain surface temperatures that allow for liquid water. There is some non-definitive evidence that this feedback has worked in Earth history, but it is untested in an exoplanet context. A critical prediction of the silicate-weathering feedback is that, on average, within the habitable zone planets that receive a higher stellar flux should have a lower CO2 in order to maintain liquid water at their surface. We can test this prediction directly by using a statistical approach involving low-precision CO2 measurements on many planets with future instruments such as JWST, LUVOIR, or HabEx. The purpose of this work is to carefully outline the requirements for such a test. First, we use a radiative-transfer model to compute the amount of CO2 necessary to maintain surface liquid water on planets for different values of insolation and planetary parameters. We run a large ensemble of Earth-like planets with different masses, atmospheric masses, inert atmospheric composition, cloud composition and level, and other greenhouse gases. Second, we post-process this data to determine the precision with which future instruments such as JWST, LUVOIR, and HabEx could measure the CO2. We then combine the variation due to planetary parameters and observational error to determine the number of planet measurements that would be needed to effectively marginalize over uncertainties and resolve the predicted trend in CO2 vs. stellar flux. The results of this work may influence the usage of JWST and will enhance mission planning for LUVOIR and HabEx.

  18. Appropriate statistical methods are required to assess diagnostic tests for replacement, add-on, and triage

    NARCIS (Netherlands)

    Hayen, Andrew; Macaskill, Petra; Irwig, Les; Bossuyt, Patrick

    2010-01-01

    To explain which measures of accuracy and which statistical methods should be used in studies to assess the value of a new binary test as a replacement test, an add-on test, or a triage test. Selection and explanation of statistical methods, illustrated with examples. Statistical methods for

  19. Decision Support Systems: Applications in Statistics and Hypothesis Testing.

    Science.gov (United States)

    Olsen, Christopher R.; Bozeman, William C.

    1988-01-01

    Discussion of the selection of appropriate statistical procedures by educators highlights a study conducted to investigate the effectiveness of decision aids in facilitating the use of appropriate statistics. Experimental groups and a control group using a printed flow chart, a computer-based decision aid, and a standard text are described. (11…

  20. Statistics

    Science.gov (United States)

    Links to sources of cancer-related statistics, including the Surveillance, Epidemiology and End Results (SEER) Program, SEER-Medicare datasets, cancer survivor prevalence data, and the Cancer Trends Progress Report.

  1. Spent fuel's behavior under dynamic drip tests

    International Nuclear Information System (INIS)

    Finn, P.A.; Buck, E.C.; Hoh, J.C.; Bates, J.K.

    1995-01-01

    In the potential repository at Yucca Mountain, failure of the waste package container and the cladding of the spent nuclear fuel would expose the fuel to water under oxidizing conditions. To simulate the release behavior of radionuclides from spent fuel, dynamic drip and vapor tests with spent nuclear fuel have been ongoing for 2.5 years. Rapid alteration of the spent fuel has been noted with concurrent release of radionuclides. Colloidal species containing americium and plutonium have been found in the leachate. This observation suggests that colloidal transport of radionuclides should be included in the performance assessment of a potential repository

  2. Examining publication bias—a simulation-based evaluation of statistical tests on publication bias

    Directory of Open Access Journals (Sweden)

    Andreas Schneck

    2017-11-01

    Full Text Available Background Publication bias is a form of scientific misconduct. It threatens the validity of research results and the credibility of science. Although several tests on publication bias exist, no in-depth evaluations are available that examine which test performs best for different research settings. Methods Four tests on publication bias, Egger’s test (FAT, p-uniform, the test of excess significance (TES, as well as the caliper test, were evaluated in a Monte Carlo simulation. Two different types of publication bias and its degree (0%, 50%, 100% were simulated. The type of publication bias was defined either as file-drawer, meaning the repeated analysis of new datasets, or p-hacking, meaning the inclusion of covariates in order to obtain a significant result. In addition, the underlying effect (β = 0, 0.5, 1, 1.5, effect heterogeneity, the number of observations in the simulated primary studies (N = 100, 500, and the number of observations for the publication bias tests (K = 100, 1,000 were varied. Results All tests evaluated were able to identify publication bias both in the file-drawer and p-hacking condition. The false positive rates were, with the exception of the 15%- and 20%-caliper test, unbiased. The FAT had the largest statistical power in the file-drawer conditions, whereas under p-hacking the TES was, except under effect heterogeneity, slightly better. The CTs were, however, inferior to the other tests under effect homogeneity and had a decent statistical power only in conditions with 1,000 primary studies. Discussion The FAT is recommended as a test for publication bias in standard meta-analyses with no or only small effect heterogeneity. If two-sided publication bias is suspected as well as under p-hacking the TES is the first alternative to the FAT. The 5%-caliper test is recommended under conditions of effect heterogeneity and a large number of primary studies, which may be found if publication bias is examined in a

  3. Statistics

    International Nuclear Information System (INIS)

    2005-01-01

    For the years 2004 and 2005 the figures shown in the tables of Energy Review are partly preliminary. The annual statistics published in Energy Review are presented in more detail in a publication called Energy Statistics that comes out yearly. Energy Statistics also includes historical time-series over a longer period of time (see e.g. Energy Statistics, Statistics Finland, Helsinki 2004.) The applied energy units and conversion coefficients are shown in the back cover of the Review. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in GDP, energy consumption and electricity consumption, Carbon dioxide emissions from fossile fuels use, Coal consumption, Consumption of natural gas, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices in heat production, Fuel prices in electricity production, Price of electricity by type of consumer, Average monthly spot prices at the Nord pool power exchange, Total energy consumption by source and CO 2 -emissions, Supplies and total consumption of electricity GWh, Energy imports by country of origin in January-June 2003, Energy exports by recipient country in January-June 2003, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Price of natural gas by type of consumer, Price of electricity by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Energy taxes, precautionary stock fees and oil pollution fees

  4. Statistics

    International Nuclear Information System (INIS)

    2001-01-01

    For the year 2000, part of the figures shown in the tables of the Energy Review are preliminary or estimated. The annual statistics of the Energy Review appear in more detail from the publication Energiatilastot - Energy Statistics issued annually, which also includes historical time series over a longer period (see e.g. Energiatilastot 1999, Statistics Finland, Helsinki 2000, ISSN 0785-3165). The inside of the Review's back cover shows the energy units and the conversion coefficients used for them. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in the volume of GNP and energy consumption, Changes in the volume of GNP and electricity, Coal consumption, Natural gas consumption, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices for heat production, Fuel prices for electricity production, Carbon dioxide emissions from the use of fossil fuels, Total energy consumption by source and CO 2 -emissions, Electricity supply, Energy imports by country of origin in 2000, Energy exports by recipient country in 2000, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Average electricity price by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Energy taxes and precautionary stock fees on oil products

  5. Statistics

    International Nuclear Information System (INIS)

    2000-01-01

    For the year 1999 and 2000, part of the figures shown in the tables of the Energy Review are preliminary or estimated. The annual statistics of the Energy Review appear in more detail from the publication Energiatilastot - Energy Statistics issued annually, which also includes historical time series over a longer period (see e.g., Energiatilastot 1998, Statistics Finland, Helsinki 1999, ISSN 0785-3165). The inside of the Review's back cover shows the energy units and the conversion coefficients used for them. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in the volume of GNP and energy consumption, Changes in the volume of GNP and electricity, Coal consumption, Natural gas consumption, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices for heat production, Fuel prices for electricity production, Carbon dioxide emissions, Total energy consumption by source and CO 2 -emissions, Electricity supply, Energy imports by country of origin in January-March 2000, Energy exports by recipient country in January-March 2000, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Average electricity price by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Energy taxes and precautionary stock fees on oil products

  6. Statistics

    International Nuclear Information System (INIS)

    1999-01-01

    For the year 1998 and the year 1999, part of the figures shown in the tables of the Energy Review are preliminary or estimated. The annual statistics of the Energy Review appear in more detail from the publication Energiatilastot - Energy Statistics issued annually, which also includes historical time series over a longer period (see e.g. Energiatilastot 1998, Statistics Finland, Helsinki 1999, ISSN 0785-3165). The inside of the Review's back cover shows the energy units and the conversion coefficients used for them. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in the volume of GNP and energy consumption, Changes in the volume of GNP and electricity, Coal consumption, Natural gas consumption, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices for heat production, Fuel prices for electricity production, Carbon dioxide emissions, Total energy consumption by source and CO 2 -emissions, Electricity supply, Energy imports by country of origin in January-June 1999, Energy exports by recipient country in January-June 1999, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Average electricity price by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Energy taxes and precautionary stock fees on oil products

  7. Statistics

    International Nuclear Information System (INIS)

    2003-01-01

    For the year 2002, part of the figures shown in the tables of the Energy Review are partly preliminary. The annual statistics of the Energy Review also includes historical time-series over a longer period (see e.g. Energiatilastot 2001, Statistics Finland, Helsinki 2002). The applied energy units and conversion coefficients are shown in the inside back cover of the Review. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in GDP, energy consumption and electricity consumption, Carbon dioxide emissions from fossile fuels use, Coal consumption, Consumption of natural gas, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices in heat production, Fuel prices in electricity production, Price of electricity by type of consumer, Average monthly spot prices at the Nord pool power exchange, Total energy consumption by source and CO 2 -emissions, Supply and total consumption of electricity GWh, Energy imports by country of origin in January-June 2003, Energy exports by recipient country in January-June 2003, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Price of natural gas by type of consumer, Price of electricity by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Excise taxes, precautionary stock fees on oil pollution fees on energy products

  8. Statistics

    International Nuclear Information System (INIS)

    2004-01-01

    For the year 2003 and 2004, the figures shown in the tables of the Energy Review are partly preliminary. The annual statistics of the Energy Review also includes historical time-series over a longer period (see e.g. Energiatilastot, Statistics Finland, Helsinki 2003, ISSN 0785-3165). The applied energy units and conversion coefficients are shown in the inside back cover of the Review. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in GDP, energy consumption and electricity consumption, Carbon dioxide emissions from fossile fuels use, Coal consumption, Consumption of natural gas, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices in heat production, Fuel prices in electricity production, Price of electricity by type of consumer, Average monthly spot prices at the Nord pool power exchange, Total energy consumption by source and CO 2 -emissions, Supplies and total consumption of electricity GWh, Energy imports by country of origin in January-March 2004, Energy exports by recipient country in January-March 2004, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Price of natural gas by type of consumer, Price of electricity by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Excise taxes, precautionary stock fees on oil pollution fees

  9. Statistics

    International Nuclear Information System (INIS)

    2000-01-01

    For the year 1999 and 2000, part of the figures shown in the tables of the Energy Review are preliminary or estimated. The annual statistics of the Energy also includes historical time series over a longer period (see e.g., Energiatilastot 1999, Statistics Finland, Helsinki 2000, ISSN 0785-3165). The inside of the Review's back cover shows the energy units and the conversion coefficients used for them. Explanatory notes to the statistical tables can be found after tables and figures. The figures presents: Changes in the volume of GNP and energy consumption, Changes in the volume of GNP and electricity, Coal consumption, Natural gas consumption, Peat consumption, Domestic oil deliveries, Import prices of oil, Consumer prices of principal oil products, Fuel prices for heat production, Fuel prices for electricity production, Carbon dioxide emissions, Total energy consumption by source and CO 2 -emissions, Electricity supply, Energy imports by country of origin in January-June 2000, Energy exports by recipient country in January-June 2000, Consumer prices of liquid fuels, Consumer prices of hard coal, natural gas and indigenous fuels, Average electricity price by type of consumer, Price of district heating by type of consumer, Excise taxes, value added taxes and fiscal charges and fees included in consumer prices of some energy sources and Energy taxes and precautionary stock fees on oil products

  10. Statistical Analysis of Geo-electric Imaging and Geotechnical Test ...

    Indian Academy of Sciences (India)

    12

    On the other hand cost-effective geoelctric imaging methods provide 2-D / 3-D .... SPSS (Statistical package for social sciences) have been used to carry out linear ..... P W J 1997 Theory of ionic surface electrical conduction in porous media;.

  11. Testing for changes using permutations of U-statistics

    Czech Academy of Sciences Publication Activity Database

    Horvath, L.; Hušková, Marie

    2005-01-01

    Roč. 2005, č. 128 (2005), s. 351-371 ISSN 0378-3758 R&D Projects: GA ČR GA201/00/0769 Institutional research plan: CEZ:AV0Z10750506 Keywords : U-statistics * permutations * change-point * weighted approximation * Brownian bridge Subject RIV: BD - Theory of Information Impact factor: 0.481, year: 2005

  12. Optimal allocation of testing resources for statistical simulations

    Science.gov (United States)

    Quintana, Carolina; Millwater, Harry R.; Singh, Gulshan; Golden, Patrick

    2015-07-01

    Statistical estimates from simulation involve uncertainty caused by the variability in the input random variables due to limited data. Allocating resources to obtain more experimental data of the input variables to better characterize their probability distributions can reduce the variance of statistical estimates. The methodology proposed determines the optimal number of additional experiments required to minimize the variance of the output moments given single or multiple constraints. The method uses multivariate t-distribution and Wishart distribution to generate realizations of the population mean and covariance of the input variables, respectively, given an amount of available data. This method handles independent and correlated random variables. A particle swarm method is used for the optimization. The optimal number of additional experiments per variable depends on the number and variance of the initial data, the influence of the variable in the output function and the cost of each additional experiment. The methodology is demonstrated using a fretting fatigue example.

  13. Understanding the Sampling Distribution and Its Use in Testing Statistical Significance.

    Science.gov (United States)

    Breunig, Nancy A.

    Despite the increasing criticism of statistical significance testing by researchers, particularly in the publication of the 1994 American Psychological Association's style manual, statistical significance test results are still popular in journal articles. For this reason, it remains important to understand the logic of inferential statistics. A…

  14. Statistical Analysis for Test Papers with Software SPSS

    Institute of Scientific and Technical Information of China (English)

    张燕君

    2012-01-01

      Test paper evaluation is an important work for the management of tests, which results are significant bases for scientific summation of teaching and learning. Taking an English test paper of high students’monthly examination as the object, it focuses on the interpretation of SPSS output concerning item and whole quantitative analysis of papers. By analyzing and evaluating the papers, it can be a feedback for teachers to check the students’progress and adjust their teaching process.

  15. Statistics of sampling for microbiological testing of foodborne pathogens

    Science.gov (United States)

    Despite the many recent advances in protocols for testing for pathogens in foods, a number of challenges still exist. For example, the microbiological safety of food cannot be completely ensured by testing because microorganisms are not evenly distributed throughout the food. Therefore, since it i...

  16. Statistical tests for equal predictive ability across multiple forecasting methods

    DEFF Research Database (Denmark)

    Borup, Daniel; Thyrsgaard, Martin

    We develop a multivariate generalization of the Giacomini-White tests for equal conditional predictive ability. The tests are applicable to a mixture of nested and non-nested models, incorporate estimation uncertainty explicitly, and allow for misspecification of the forecasting model as well as ...

  17. Statistical analysis of nematode counts from interlaboratory proficiency tests

    NARCIS (Netherlands)

    Berg, van den W.; Hartsema, O.; Nijs, Den J.M.F.

    2014-01-01

    A series of proficiency tests on potato cyst nematode (PCN; n=29) and free-living stages of Meloidogyne and Pratylenchus (n=23) were investigated to determine the accuracy and precision of the nematode counts and to gain insights into possible trends and potential improvements. In each test, each

  18. Jsub(Ic)-testing of A-533 B - statistical evaluation of some different testing techniques

    International Nuclear Information System (INIS)

    Nilsson, F.

    1978-01-01

    The purpose of the present study was to compare statistically some different methods for the evaluation of fracture toughness of the nuclear reactor material A-533 B. Since linear elastic fracture mechanics is not applicable to this material at the interesting temperature (275 0 C), the so-called Jsub(Ic) testing method was employed. Two main difficulties are inherent in this type of testing. The first one is to determine the quantity J as a function of the deflection of the three-point bend specimens used. Three different techniques were used, the first two based on the experimentally observed input of energy to the specimen and the third employing finite element calculations. The second main problem is to determine the point when crack growth begins. For this, two methods were used, a direct electrical method and the indirect R-curve method. A total of forty specimens were tested at two laboratories. No statistically significant different results were obtained from the respective laboratories. The three methods of calculating J yielded somewhat different results, although the discrepancy was small. Also the two methods of determination of the growth initiation point yielded consistent results. The R-curve method, however, exhibited a larger uncertainty as measured by the standard deviation. The resulting Jsub(Ic) value also agreed well with earlier presented results. The relative standard deviation was of the order of 25%, which is quite small for this type of experiment. (author)

  19. Statistics applied to the testing of cladding tubes

    International Nuclear Information System (INIS)

    Perdijon, J.

    1987-01-01

    Cladding tubes, either steel or zircaloy, are generally given a 100 % inspection through ultrasonic non-destructive testing. This inspection may be completed beneficially with an eddy current test, as this is not sensitive to the same defects as those typically traced by ultrasonic testing. Unfortunately, the two methods (as with other non-destructive tests) exhibit poor precision; this means that a flaw, whose size is close to that denoted as rejection limit, may be accepted or rejected. Currently, rejection, i.e. the measurement above which a tube is rejected, is generally determined through measuring a calibration tube at regular time intervals, and the signal of a given tube is compared to that of the most recently completed calibration. This measurement is thus subject to variations which can be attributed to an actual shift of adjustments as well as to poor precision. For this reason, monitoring instrument adjustments using the so-called control chart method are proposed

  20. Statistical modeling of dental unit water bacterial test kit performance.

    Science.gov (United States)

    Cohen, Mark E; Harte, Jennifer A; Stone, Mark E; O'Connor, Karen H; Coen, Michael L; Cullum, Malford E

    2007-01-01

    While it is important to monitor dental water quality, it is unclear whether in-office test kits provide bacterial counts comparable to the gold standard method (R2A). Studies were conducted on specimens with known bacterial concentrations, and from dental units, to evaluate test kit accuracy across a range of bacterial types and loads. Colony forming units (CFU) were counted for samples from each source, using R2A and two types of test kits, and conformity to Poisson distribution expectations was evaluated. Poisson regression was used to test for effects of source and device, and to estimate rate ratios for kits relative to R2A. For all devices, distributions were Poisson for low CFU/mL when only beige-pigmented bacteria were considered. For higher counts, R2A remained Poisson, but kits exhibited over-dispersion. Both kits undercounted relative to R2A, but the degree of undercounting was reasonably stable. Kits did not grow pink-pigmented bacteria from dental-unit water identified as Methylobacterium rhodesianum. Only one of the test kits provided results with adequate reliability at higher bacterial concentrations. Undercount bias could be estimated for this device and used to adjust test kit results. Insensitivity to methylobacteria spp. is problematic.

  1. STATISTICAL EVALUATION OF EXAMINATION TESTS IN MATHEMATICS FOR ECONOMISTS

    Directory of Open Access Journals (Sweden)

    KASPŘÍKOVÁ, Nikola

    2012-12-01

    Full Text Available Examination results are rather important for many students with regard to their future profession development. Results of exams should be carefully inspected by the teachers to help improve design and evaluation of tests and education process in general. Analysis of examination papers in mathematics taken by students of basic mathematics course at University of Economics in Prague is reported. The first issue addressed is identification of significant dependencies between performance in particular problem areas covered in the test and also between particular items and total score in test or ability level as a latent trait. The assessment is first performed with Spearman correlation coefficient, items in the test are then evaluated within Item Response Theory framework. The second analytical task addressed is a search for groups of students who are similar with respect to performance in test. Cluster analysis is performed using partitioning around medoids method and final model selection is made according to average silhouette width. Results of clustering, which may be also considered in connection with setting of the minimum score for passing the exam, show that two groups of students can be identified. The group which may be called "well-performers" is the more clearly defined one.

  2. Statistical thermodynamics and mean-field theory for the alloy under irradiation model

    International Nuclear Information System (INIS)

    Kamyshendo, V.

    1993-01-01

    A generalization of statistical thermodynamics to the open systems case, is discussed, using as an example the alloy-under-irradiation model. The statistical properties of stationary states are described with the use of generalized thermodynamic potentials and 'quasi-interactions' determined from the master equation for micro-configuration probabilities. Methods for resolving this equation are illustrated by the mean-field type calculations of correlators, thermodynamic potentials and phase diagrams for disordered alloys

  3. Approximations to the distribution of a test statistic in covariance structure analysis: A comprehensive study.

    Science.gov (United States)

    Wu, Hao

    2018-05-01

    In structural equation modelling (SEM), a robust adjustment to the test statistic or to its reference distribution is needed when its null distribution deviates from a χ 2 distribution, which usually arises when data do not follow a multivariate normal distribution. Unfortunately, existing studies on this issue typically focus on only a few methods and neglect the majority of alternative methods in statistics. Existing simulation studies typically consider only non-normal distributions of data that either satisfy asymptotic robustness or lead to an asymptotic scaled χ 2 distribution. In this work we conduct a comprehensive study that involves both typical methods in SEM and less well-known methods from the statistics literature. We also propose the use of several novel non-normal data distributions that are qualitatively different from the non-normal distributions widely used in existing studies. We found that several under-studied methods give the best performance under specific conditions, but the Satorra-Bentler method remains the most viable method for most situations. © 2017 The British Psychological Society.

  4. After statistics reform : Should we still teach significance testing?

    NARCIS (Netherlands)

    A. Hak (Tony)

    2014-01-01

    textabstractIn the longer term null hypothesis significance testing (NHST) will disappear because p- values are not informative and not replicable. Should we continue to teach in the future the procedures of then abolished routines (i.e., NHST)? Three arguments are discussed for not teaching NHST in

  5. Statistical Tests for Frequency Distribution of Mean Gravity Anomalies

    African Journals Online (AJOL)

    The hypothesis that a very large number of lOx 10mean gravity anomalies are normally distributed has been rejected at 5% Significance level based on the X2 and the unit normal deviate tests. However, the 50 equal area mean anomalies derived from the lOx 10data, have been found to be normally distributed at the same ...

  6. Testing the performance of a blind burst statistic

    Energy Technology Data Exchange (ETDEWEB)

    Vicere, A [Istituto di Fisica, Universita di Urbino (Italy); Calamai, G [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Campagna, E [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Conforto, G [Istituto di Fisica, Universita di Urbino (Italy); Cuoco, E [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Dominici, P [Istituto di Fisica, Universita di Urbino (Italy); Fiori, I [Istituto di Fisica, Universita di Urbino (Italy); Guidi, G M [Istituto di Fisica, Universita di Urbino (Italy); Losurdo, G [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Martelli, F [Istituto di Fisica, Universita di Urbino (Italy); Mazzoni, M [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Perniola, B [Istituto di Fisica, Universita di Urbino (Italy); Stanga, R [Istituto Nazionale di Fisica Nucleare, Sez. Firenze/Urbino (Italy); Vetrano, F [Istituto di Fisica, Universita di Urbino (Italy)

    2003-09-07

    In this work, we estimate the performance of a method for the detection of burst events in the data produced by interferometric gravitational wave detectors. We compute the receiver operating characteristics in the specific case of a simulated noise having the spectral density expected for Virgo, using test signals taken from a library of possible waveforms emitted during the collapse of the core of type II supernovae.

  7. Caracterização estatística de variáveis usadas para ensaiar uma semeadora-adubadora em semeadura direta e convencional = Statistical characterization of variables used to test a planter under direct and conventional sowing systems

    Directory of Open Access Journals (Sweden)

    Geraldo do Amaral Gravina

    2009-10-01

    Full Text Available O objetivo deste trabalho foi caracterizar, estatisticamente, as variáveis patinagem dos rodados, espaço percorrido por parcela, área da parcela trabalhada,capacidade de campo teórica e efetiva de uma semeadora em sistema de semeadura direta (SD e convencional (SC, com base na verificação do ajuste de uma série de dados a uma distribuição estatística, visando indicar a melhor forma de representação e valores a serem adotados para que estas variáveis sejam utilizadas em operações de práticas agrícolas. O experimento na SC foi realizado com velocidade de 1,5 m s-1, com 190 repetições, durante a semeadura de milho em solo classificado como Cambissolo; oexperimento na SD, com 1,8 m s-1 e 58 repetições, durante a semeadura de sorgo em solo classificado como Latossolo Vermelho-Amarelo. Concluiu-se que não foram detectados valores discrepantes e que as variáveis em estudo podem ser representadas pela função densidade de probabilidade normal (Distribuição de Gauss, podendo ser utilizados parâmetros para suas representações.Statistical characterization of variables used to test a planter under direct and conventional sowing systems. The objective of this work was to statistically characterize variables such as wheels slip, theoretical and effective field capacity of a planter in direct (DS and conventional sowing (CS systems, based on the verification of the adjustment of a series of data to a statistical distribution, aiming for the best form of representation and values be adopted so that these variables be used in agricultural practices operations. The experiment in CS was done with a speed of 1.5 m s-1 with 190 repetitions, and the experiment in DS was done with 1.8 m s-1 and58 repetitions. It was concluded that differing values were not detected, and the variables in study can be represented by the function density of normal probability (Gaussian distribution, and the variables can be used for its representations.

  8. A weighted generalized score statistic for comparison of predictive values of diagnostic tests.

    Science.gov (United States)

    Kosinski, Andrzej S

    2013-03-15

    Positive and negative predictive values are important measures of a medical diagnostic test performance. We consider testing equality of two positive or two negative predictive values within a paired design in which all patients receive two diagnostic tests. The existing statistical tests for testing equality of predictive values are either Wald tests based on the multinomial distribution or the empirical Wald and generalized score tests within the generalized estimating equations (GEE) framework. As presented in the literature, these test statistics have considerably complex formulas without clear intuitive insight. We propose their re-formulations that are mathematically equivalent but algebraically simple and intuitive. As is clearly seen with a new re-formulation we presented, the generalized score statistic does not always reduce to the commonly used score statistic in the independent samples case. To alleviate this, we introduce a weighted generalized score (WGS) test statistic that incorporates empirical covariance matrix with newly proposed weights. This statistic is simple to compute, always reduces to the score statistic in the independent samples situation, and preserves type I error better than the other statistics as demonstrated by simulations. Thus, we believe that the proposed WGS statistic is the preferred statistic for testing equality of two predictive values and for corresponding sample size computations. The new formulas of the Wald statistics may be useful for easy computation of confidence intervals for difference of predictive values. The introduced concepts have potential to lead to development of the WGS test statistic in a general GEE setting. Copyright © 2012 John Wiley & Sons, Ltd.

  9. Monte Carlo testing in spatial statistics, with applications to spatial residuals

    DEFF Research Database (Denmark)

    Mrkvička, Tomáš; Soubeyrand, Samuel; Myllymäki, Mari

    2016-01-01

    This paper reviews recent advances made in testing in spatial statistics and discussed at the Spatial Statistics conference in Avignon 2015. The rank and directional quantile envelope tests are discussed and practical rules for their use are provided. These tests are global envelope tests...... with an appropriate type I error probability. Two novel examples are given on their usage. First, in addition to the test based on a classical one-dimensional summary function, the goodness-of-fit of a point process model is evaluated by means of the test based on a higher dimensional functional statistic, namely...

  10. Normality Tests for Statistical Analysis: A Guide for Non-Statisticians

    Science.gov (United States)

    Ghasemi, Asghar; Zahediasl, Saleh

    2012-01-01

    Statistical errors are common in scientific literature and about 50% of the published articles have at least one error. The assumption of normality needs to be checked for many statistical procedures, namely parametric tests, because their validity depends on it. The aim of this commentary is to overview checking for normality in statistical analysis using SPSS. PMID:23843808

  11. Distinguishing Entailment and Presupposition Under Negation Test

    Directory of Open Access Journals (Sweden)

    Gatri Asti Putri Indarti

    2016-12-01

    Full Text Available Distinguishing entailment from presupposition is quite difficult because their semantic relation seems to be similar. Both entailment and presupposition have an automatic relationship based on the context. However, those semantic relations can still be differentiated by using negation test to show whether a pair is entailment or presupposition. This research focuses on sentences and utterances. Thus, this research aims to analyze and test pairs of entailment and pairs of presupposition by using negation in utterances. The data were twelve comic strips from the Internet and they were analysed by using a negation test. The analysis shows that negation test is useful to test entailment and presupposition in the comic strips. It can be concluded that the difficulty of distinguishing pair of entailment and presupposition in the comic strip using negation test has been successfully solved. In this case, negation test is suitable to test entailment and presupposition. This research can be developed further by other researchers to distinguish entailment and presupposition by using another test if the negation test cannot be used to any further extent.   DOI: https://doi.org/10.24071/llt.2015.180104

  12. A new efficient statistical test for detecting variability in the gene expression data.

    Science.gov (United States)

    Mathur, Sunil; Dolo, Samuel

    2008-08-01

    DNA microarray technology allows researchers to monitor the expressions of thousands of genes under different conditions. The detection of differential gene expression under two different conditions is very important in microarray studies. Microarray experiments are multi-step procedures and each step is a potential source of variance. This makes the measurement of variability difficult because approach based on gene-by-gene estimation of variance will have few degrees of freedom. It is highly possible that the assumption of equal variance for all the expression levels may not hold. Also, the assumption of normality of gene expressions may not hold. Thus it is essential to have a statistical procedure which is not based on the normality assumption and also it can detect genes with differential variance efficiently. The detection of differential gene expression variance will allow us to identify experimental variables that affect different biological processes and accuracy of DNA microarray measurements.In this article, a new nonparametric test for scale is developed based on the arctangent of the ratio of two expression levels. Most of the tests available in literature require the assumption of normal distribution, which makes them inapplicable in many situations, and it is also hard to verify the suitability of the normal distribution assumption for the given data set. The proposed test does not require the assumption of the distribution for the underlying population and hence makes it more practical and widely applicable. The asymptotic relative efficiency is calculated under different distributions, which show that the proposed test is very powerful when the assumption of normality breaks down. Monte Carlo simulation studies are performed to compare the power of the proposed test with some of the existing procedures. It is found that the proposed test is more powerful than commonly used tests under almost all the distributions considered in the study. A

  13. Using Relative Statistics and Approximate Disease Prevalence to Compare Screening Tests.

    Science.gov (United States)

    Samuelson, Frank; Abbey, Craig

    2016-11-01

    Schatzkin et al. and other authors demonstrated that the ratios of some conditional statistics such as the true positive fraction are equal to the ratios of unconditional statistics, such as disease detection rates, and therefore we can calculate these ratios between two screening tests on the same population even if negative test patients are not followed with a reference procedure and the true and false negative rates are unknown. We demonstrate that this same property applies to an expected utility metric. We also demonstrate that while simple estimates of relative specificities and relative areas under ROC curves (AUC) do depend on the unknown negative rates, we can write these ratios in terms of disease prevalence, and the dependence of these ratios on a posited prevalence is often weak particularly if that prevalence is small or the performance of the two screening tests is similar. Therefore we can estimate relative specificity or AUC with little loss of accuracy, if we use an approximate value of disease prevalence.

  14. Statistical modeling of urban air temperature distributions under different synoptic conditions

    Science.gov (United States)

    Beck, Christoph; Breitner, Susanne; Cyrys, Josef; Hald, Cornelius; Hartz, Uwe; Jacobeit, Jucundus; Richter, Katja; Schneider, Alexandra; Wolf, Kathrin

    2015-04-01

    Within urban areas air temperature may vary distinctly between different locations. These intra-urban air temperature variations partly reach magnitudes that are relevant with respect to human thermal comfort. Therefore and furthermore taking into account potential interrelations with other health related environmental factors (e.g. air quality) it is important to estimate spatial patterns of intra-urban air temperature distributions that may be incorporated into urban planning processes. In this contribution we present an approach to estimate spatial temperature distributions in the urban area of Augsburg (Germany) by means of statistical modeling. At 36 locations in the urban area of Augsburg air temperatures are measured with high temporal resolution (4 min.) since December 2012. These 36 locations represent different typical urban land use characteristics in terms of varying percentage coverages of different land cover categories (e.g. impervious, built-up, vegetated). Percentage coverages of these land cover categories have been extracted from different sources (Open Street Map, European Urban Atlas, Urban Morphological Zones) for regular grids of varying size (50, 100, 200 meter horizonal resolution) for the urban area of Augsburg. It is well known from numerous studies that land use characteristics have a distinct influence on air temperature and as well other climatic variables at a certain location. Therefore air temperatures at the 36 locations are modeled utilizing land use characteristics (percentage coverages of land cover categories) as predictor variables in Stepwise Multiple Regression models and in Random Forest based model approaches. After model evaluation via cross-validation appropriate statistical models are applied to gridded land use data to derive spatial urban air temperature distributions. Varying models are tested and applied for different seasons and times of the day and also for different synoptic conditions (e.g. clear and calm

  15. Statistical correlation of structural mode shapes from test measurements and NASTRAN analytical values

    Science.gov (United States)

    Purves, L.; Strang, R. F.; Dube, M. P.; Alea, P.; Ferragut, N.; Hershfeld, D.

    1983-01-01

    The software and procedures of a system of programs used to generate a report of the statistical correlation between NASTRAN modal analysis results and physical tests results from modal surveys are described. Topics discussed include: a mathematical description of statistical correlation, a user's guide for generating a statistical correlation report, a programmer's guide describing the organization and functions of individual programs leading to a statistical correlation report, and a set of examples including complete listings of programs, and input and output data.

  16. "What If" Analyses: Ways to Interpret Statistical Significance Test Results Using EXCEL or "R"

    Science.gov (United States)

    Ozturk, Elif

    2012-01-01

    The present paper aims to review two motivations to conduct "what if" analyses using Excel and "R" to understand the statistical significance tests through the sample size context. "What if" analyses can be used to teach students what statistical significance tests really do and in applied research either prospectively to estimate what sample size…

  17. The Testing Effect under Divided Attention

    Science.gov (United States)

    Buchin, Zachary L.; Mulligan, Neil W.

    2017-01-01

    Memory retrieval often enhances later memory compared with restudying (i.e., the testing effect), indicating that retrieval does not simply reveal but also modifies memory representations. Dividing attention (DA) during encoding greatly disrupts later memory performance while DA during retrieval typically has modest effects--but what of the…

  18. Structural Behavior Under Precision Impact Tests

    Science.gov (United States)

    1996-08-01

    ASPECTS OF IMPACT TESTING The problem of impact between two bodies has been studied extensively (for example, Eibl 1987, Feyerabend 1988, Krauthammer...Concrete for Hazard Protection, Edinburgh, Scotland, pp. 175-186. Feyerabend , M., 1988, "Der harte Querstoss auf Stützen aus Stahl und Stahlbeton

  19. Containment bellows testing under extreme loads

    International Nuclear Information System (INIS)

    Splezter, B.L.; Lambert, L.D.; Parks, M.B.

    1993-01-01

    Sandia National Laboratories (SNL) is conducting several research programs to help develop validated methods for the prediction of the ultimate pressure capacity, at elevated temperatures, of light water reactor (LWR) containment structures. To help understand the ultimate pressure of the entire containment pressure boundary, each component must be evaluated. The containment pressure boundary consists of the containment shell and many access, piping, and electrical penetrations. The focus of the current research program is to study the ultimate behavior of flexible metal bellows that are used at piping penetrations. Bellows are commonly used at piping penetrations in steel containments; however, they have very few applications in concrete (reinforced or prestressed) containments. The purpose of piping bellows is to provide a soft connection between the containment shell and the pipe are attached while maintaining the containment pressure boundary. In this way, piping loads caused by differential movement between the piping and the containment shell are minimized. SNL is conducting a test program to determine the leaktight capacity of containment bellows when subjected to postulated severe accident conditions. If the test results indicate that containment bellows could be a possible failure mode of the containment pressure boundary, then methods will be developed to predict the deformation, pressure, and temperature conditions that would likely cause a bellows failure. Results from the test program would be used to validate the prediction methods. This paper provides a description of the use and design of bellows in containment piping penetrations, the types of possible bellows loadings during a severe accident, and an overview of the test program, including available test results at the time of writing

  20. Intelligent Condition Diagnosis Method Based on Adaptive Statistic Test Filter and Diagnostic Bayesian Network.

    Science.gov (United States)

    Li, Ke; Zhang, Qiuju; Wang, Kun; Chen, Peng; Wang, Huaqing

    2016-01-08

    A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF) and Diagnostic Bayesian Network (DBN) is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal) and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO). To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA) is proposed to evaluate the sensitiveness of symptom parameters (SPs) for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN) theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method.

  1. Intelligent Condition Diagnosis Method Based on Adaptive Statistic Test Filter and Diagnostic Bayesian Network

    Directory of Open Access Journals (Sweden)

    Ke Li

    2016-01-01

    Full Text Available A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF and Diagnostic Bayesian Network (DBN is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO. To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA is proposed to evaluate the sensitiveness of symptom parameters (SPs for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method.

  2. Intelligent Condition Diagnosis Method Based on Adaptive Statistic Test Filter and Diagnostic Bayesian Network

    Science.gov (United States)

    Li, Ke; Zhang, Qiuju; Wang, Kun; Chen, Peng; Wang, Huaqing

    2016-01-01

    A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF) and Diagnostic Bayesian Network (DBN) is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal) and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO). To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA) is proposed to evaluate the sensitiveness of symptom parameters (SPs) for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN) theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method. PMID:26761006

  3. Statistical Redundancy Testing for Improved Gene Selection in Cancer Classification Using Microarray Data

    Directory of Open Access Journals (Sweden)

    J. Sunil Rao

    2007-01-01

    Full Text Available In gene selection for cancer classifi cation using microarray data, we define an eigenvalue-ratio statistic to measure a gene’s contribution to the joint discriminability when this gene is included into a set of genes. Based on this eigenvalueratio statistic, we define a novel hypothesis testing for gene statistical redundancy and propose two gene selection methods. Simulation studies illustrate the agreement between statistical redundancy testing and gene selection methods. Real data examples show the proposed gene selection methods can select a compact gene subset which can not only be used to build high quality cancer classifiers but also show biological relevance.

  4. Surprise responses in the human brain demonstrate statistical learning under high concurrent cognitive demand

    Science.gov (United States)

    Garrido, Marta Isabel; Teng, Chee Leong James; Taylor, Jeremy Alexander; Rowe, Elise Genevieve; Mattingley, Jason Brett

    2016-06-01

    The ability to learn about regularities in the environment and to make predictions about future events is fundamental for adaptive behaviour. We have previously shown that people can implicitly encode statistical regularities and detect violations therein, as reflected in neuronal responses to unpredictable events that carry a unique prediction error signature. In the real world, however, learning about regularities will often occur in the context of competing cognitive demands. Here we asked whether learning of statistical regularities is modulated by concurrent cognitive load. We compared electroencephalographic metrics associated with responses to pure-tone sounds with frequencies sampled from narrow or wide Gaussian distributions. We showed that outliers evoked a larger response than those in the centre of the stimulus distribution (i.e., an effect of surprise) and that this difference was greater for physically identical outliers in the narrow than in the broad distribution. These results demonstrate an early neurophysiological marker of the brain's ability to implicitly encode complex statistical structure in the environment. Moreover, we manipulated concurrent cognitive load by having participants perform a visual working memory task while listening to these streams of sounds. We again observed greater prediction error responses in the narrower distribution under both low and high cognitive load. Furthermore, there was no reliable reduction in prediction error magnitude under high-relative to low-cognitive load. Our findings suggest that statistical learning is not a capacity limited process, and that it proceeds automatically even when cognitive resources are taxed by concurrent demands.

  5. Testing Genetic Pleiotropy with GWAS Summary Statistics for Marginal and Conditional Analyses.

    Science.gov (United States)

    Deng, Yangqing; Pan, Wei

    2017-12-01

    There is growing interest in testing genetic pleiotropy, which is when a single genetic variant influences multiple traits. Several methods have been proposed; however, these methods have some limitations. First, all the proposed methods are based on the use of individual-level genotype and phenotype data; in contrast, for logistical, and other, reasons, summary statistics of univariate SNP-trait associations are typically only available based on meta- or mega-analyzed large genome-wide association study (GWAS) data. Second, existing tests are based on marginal pleiotropy, which cannot distinguish between direct and indirect associations of a single genetic variant with multiple traits due to correlations among the traits. Hence, it is useful to consider conditional analysis, in which a subset of traits is adjusted for another subset of traits. For example, in spite of substantial lowering of low-density lipoprotein cholesterol (LDL) with statin therapy, some patients still maintain high residual cardiovascular risk, and, for these patients, it might be helpful to reduce their triglyceride (TG) level. For this purpose, in order to identify new therapeutic targets, it would be useful to identify genetic variants with pleiotropic effects on LDL and TG after adjusting the latter for LDL; otherwise, a pleiotropic effect of a genetic variant detected by a marginal model could simply be due to its association with LDL only, given the well-known correlation between the two types of lipids. Here, we develop a new pleiotropy testing procedure based only on GWAS summary statistics that can be applied for both marginal analysis and conditional analysis. Although the main technical development is based on published union-intersection testing methods, care is needed in specifying conditional models to avoid invalid statistical estimation and inference. In addition to the previously used likelihood ratio test, we also propose using generalized estimating equations under the

  6. Statistical inferences under the Null hypothesis: Common mistakes and pitfalls in neuroimaging studies.

    Directory of Open Access Journals (Sweden)

    Jean-Michel eHupé

    2015-02-01

    Full Text Available Published studies using functional and structural MRI include many errors in the way data are analyzed and conclusions reported. This was observed when working on a comprehensive review of the neural bases of synesthesia, but these errors are probably endemic to neuroimaging studies. All studies reviewed had based their conclusions using Null Hypothesis Significance Tests (NHST. NHST have yet been criticized since their inception because they are more appropriate for taking decisions related to a Null hypothesis (like in manufacturing than for making inferences about behavioral and neuronal processes. Here I focus on a few key problems of NHST related to brain imaging techniques, and explain why or when we should not rely on significance tests. I also observed that, often, the ill-posed logic of NHST was even not correctly applied, and describe what I identified as common mistakes or at least problematic practices in published papers, in light of what could be considered as the very basics of statistical inference. MRI statistics also involve much more complex issues than standard statistical inference. Analysis pipelines vary a lot between studies, even for those using the same software, and there is no consensus which pipeline is the best. I propose a synthetic view of the logic behind the possible methodological choices, and warn against the usage and interpretation of two statistical methods popular in brain imaging studies, the false discovery rate (FDR procedure and permutation tests. I suggest that current models for the analysis of brain imaging data suffer from serious limitations and call for a revision taking into account the new statistics (confidence intervals logic.

  7. Ensuring Positiveness of the Scaled Difference Chi-square Test Statistic.

    Science.gov (United States)

    Satorra, Albert; Bentler, Peter M

    2010-06-01

    A scaled difference test statistic [Formula: see text] that can be computed from standard software of structural equation models (SEM) by hand calculations was proposed in Satorra and Bentler (2001). The statistic [Formula: see text] is asymptotically equivalent to the scaled difference test statistic T̄(d) introduced in Satorra (2000), which requires more involved computations beyond standard output of SEM software. The test statistic [Formula: see text] has been widely used in practice, but in some applications it is negative due to negativity of its associated scaling correction. Using the implicit function theorem, this note develops an improved scaling correction leading to a new scaled difference statistic T̄(d) that avoids negative chi-square values.

  8. Game Related Statistics Which Discriminate Between Winning and Losing Under-16 Male Basketball Games

    Science.gov (United States)

    Lorenzo, Alberto; Gómez, Miguel Ángel; Ortega, Enrique; Ibáñez, Sergio José; Sampaio, Jaime

    2010-01-01

    The aim of the present study was to identify the game-related statistics which discriminate between winning and losing teams in under-16 years old male basketball games. The sample gathered all 122 games in the 2004 and 2005 Under-16 European Championships. The game-related statistics analysed were the free-throws (both successful and unsuccessful), 2- and 3-points field-goals (both successful and unsuccessful) offensive and defensive rebounds, blocks, assists, fouls, turnovers and steals. The winning teams exhibited lower ball possessions per game and better offensive and defensive efficacy coefficients than the losing teams. Results from discriminant analysis were statistically significant and allowed to emphasize several structure coefficients (SC). In close games (final score differences below 9 points), the discriminant variables were the turnovers (SC = -0.47) and the assists (SC = 0.33). In balanced games (final score differences between 10 and 29 points), the variables that discriminated between the groups were the successful 2-point field-goals (SC = -0.34) and defensive rebounds (SC = -0. 36); and in unbalanced games (final score differences above 30 points) the variables that best discriminated both groups were the successful 2-point field-goals (SC = 0.37). These results allowed understanding that these players' specific characteristics result in a different game-related statistical profile and helped to point out the importance of the perceptive and decision making process in practice and in competition. Key points The players' game-related statistical profile varied according to game type, game outcome and in formative categories in basketball. The results of this work help to point out the different player's performance described in U-16 men's basketball teams compared with senior and professional men's basketball teams. The results obtained enhance the importance of the perceptive and decision making process in practice and in competition. PMID

  9. Selecting the most appropriate inferential statistical test for your quantitative research study.

    Science.gov (United States)

    Bettany-Saltikov, Josette; Whittaker, Victoria Jane

    2014-06-01

    To discuss the issues and processes relating to the selection of the most appropriate statistical test. A review of the basic research concepts together with a number of clinical scenarios is used to illustrate this. Quantitative nursing research generally features the use of empirical data which necessitates the selection of both descriptive and statistical tests. Different types of research questions can be answered by different types of research designs, which in turn need to be matched to a specific statistical test(s). Discursive paper. This paper discusses the issues relating to the selection of the most appropriate statistical test and makes some recommendations as to how these might be dealt with. When conducting empirical quantitative studies, a number of key issues need to be considered. Considerations for selecting the most appropriate statistical tests are discussed and flow charts provided to facilitate this process. When nursing clinicians and researchers conduct quantitative research studies, it is crucial that the most appropriate statistical test is selected to enable valid conclusions to be made. © 2013 John Wiley & Sons Ltd.

  10. A testing procedure for wind turbine generators based on the power grid statistical model

    DEFF Research Database (Denmark)

    Farajzadehbibalan, Saber; Ramezani, Mohammad Hossein; Nielsen, Peter

    2017-01-01

    In this study, a comprehensive test procedure is developed to test wind turbine generators with a hardware-in-loop setup. The procedure employs the statistical model of the power grid considering the restrictions of the test facility and system dynamics. Given the model in the latent space...

  11. Common pitfalls in statistical analysis: Understanding the properties of diagnostic tests - Part 1.

    Science.gov (United States)

    Ranganathan, Priya; Aggarwal, Rakesh

    2018-01-01

    In this article in our series on common pitfalls in statistical analysis, we look at some of the attributes of diagnostic tests (i.e., tests which are used to determine whether an individual does or does not have disease). The next article in this series will focus on further issues related to diagnostic tests.

  12. Subcritical tests - nuclear weapon testing under the Comprehensive Test Ban Treaty; Subkritiske tester - kjernevaapentesting under avtalen om fullstendig proevestans

    Energy Technology Data Exchange (ETDEWEB)

    Hoeibraaten, S

    1998-10-01

    The report discusses possible nuclear weapons related experiments and whether these are permitted under the 1996 Comprehensive Test Ban Treaty (CTBT). The term ''subcritical experiments'' as used in the United States includes experiments in which one studies fissile materials (so far only plutonium) under extreme conditions generated by conventional high explosives, and in which a self-sustained chain reaction never develops in the fissile material. The known facts about the American subcritical experiments are presented. There is very little reason to doubt that these experiments were indeed subcritical and therefore permitted under the CTBT. Little is known about the Russian efforts that are being made on subcritical experiments.

  13. Subcritical tests - nuclear weapon testing under the Comprehensive Test Ban Treaty

    International Nuclear Information System (INIS)

    Hoeibraaten, S.

    1998-10-01

    The report discusses possible nuclear weapons related experiments and whether these are permitted under the 1996 Comprehensive Test Ban Treaty (CTBT). The term ''subcritical experiments'' as used in the United States includes experiments in which one studies fissile materials (so far only plutonium) under extreme conditions generated by conventional high explosives, and in which a self-sustained chain reaction never develops in the fissile material. The known facts about the American subcritical experiments are presented. There is very little reason to doubt that these experiments were indeed subcritical and therefore permitted under the CTBT. Little is known about the Russian efforts that are being made on subcritical experiments

  14. The Relationship between Test Anxiety and Academic Performance of Students in Vital Statistics Course

    Directory of Open Access Journals (Sweden)

    Shirin Iranfar

    2013-12-01

    Full Text Available Introduction: Test anxiety is a common phenomenon among students and is one of the problems of educational system. The present study was conducted to investigate the test anxiety in vital statistics course and its association with academic performance of students at Kermanshah University of Medical Sciences. This study was descriptive-analytical and the study sample included the students studying in nursing and midwifery, paramedicine and health faculties that had taken vital statistics course and were selected through census method. Sarason questionnaire was used to analyze the test anxiety. Data were analyzed by descriptive and inferential statistics. The findings indicated no significant correlation between test anxiety and score of vital statistics course.

  15. A Modified Jonckheere Test Statistic for Ordered Alternatives in Repeated Measures Design

    Directory of Open Access Journals (Sweden)

    Hatice Tül Kübra AKDUR

    2016-09-01

    Full Text Available In this article, a new test based on Jonckheere test [1] for  randomized blocks which have dependent observations within block is presented. A weighted sum for each block statistic rather than the unweighted sum proposed by Jonckheereis included. For Jonckheere type statistics, the main assumption is independency of observations within block. In the case of repeated measures design, the assumption of independence is violated. The weighted Jonckheere type statistic for the situation of dependence for different variance-covariance structure and the situation based on ordered alternative hypothesis structure of each block on the design is used. Also, the proposed statistic is compared to the existing test based on Jonckheere in terms of type I error rates by performing Monte Carlo simulation. For the strong correlations, circular bootstrap version of the proposed Jonckheere test provides lower rates of type I error.

  16. The Statistic Test on Influence of Surface Treatment to Fatigue Lifetime with Limited Data

    OpenAIRE

    Suhartono, Agus

    2009-01-01

    Justifications on the influences of two or more parameters on fatigue strength are some times problematic due to the scatter nature of the fatigue data. Statistic test can facilitate the evaluation, whether the changes in material characteristics as a result of specific parameters of interest is significant. The statistic tests were applied to fatigue data of AISI 1045 steel specimens. The specimens are consisted of as received specimen, shot peened specimen with 15 and 16 Almen intensity as ...

  17. Co-integration Rank Testing under Conditional Heteroskedasticity

    DEFF Research Database (Denmark)

    Cavaliere, Guiseppe; Rahbæk, Anders; Taylor, A.M. Robert

    null distributions of the rank statistics coincide with those derived by previous authors who assume either i.i.d. or (strict and covariance) stationary martingale difference innovations. We then propose wild bootstrap implementations of the co-integrating rank tests and demonstrate that the associated...... bootstrap rank statistics replicate the first-order asymptotic null distributions of the rank statistics. We show the same is also true of the corresponding rank tests based on the i.i.d. bootstrap of Swensen (2006). The wild bootstrap, however, has the important property that, unlike the i.i.d. bootstrap......, it preserves in the re-sampled data the pattern of heteroskedasticity present in the original shocks. Consistent with this, numerical evidence sug- gests that, relative to tests based on the asymptotic critical values or the i.i.d. bootstrap, the wild bootstrap rank tests perform very well in small samples un...

  18. Ion induced electron emission statistics under Agm- cluster bombardment of Ag

    Science.gov (United States)

    Breuers, A.; Penning, R.; Wucher, A.

    2018-05-01

    The electron emission from a polycrystalline silver surface under bombardment with Agm- cluster ions (m = 1, 2, 3) is investigated in terms of ion induced kinetic excitation. The electron yield γ is determined directly by a current measurement method on the one hand and implicitly by the analysis of the electron emission statistics on the other hand. Successful measurements of the electron emission spectra ensure a deeper understanding of the ion induced kinetic electron emission process, with particular emphasis on the effect of the projectile cluster size to the yield as well as to emission statistics. The results allow a quantitative comparison to computer simulations performed for silver atoms and clusters impinging onto a silver surface.

  19. Comment on the asymptotics of a distribution-free goodness of fit test statistic.

    Science.gov (United States)

    Browne, Michael W; Shapiro, Alexander

    2015-03-01

    In a recent article Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed that a proof by Browne (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) of the asymptotic distribution of a goodness of fit test statistic is incomplete because it fails to prove that the orthogonal component function employed is continuous. Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed how Browne's proof can be completed satisfactorily but this required the development of an extensive and mathematically sophisticated framework for continuous orthogonal component functions. This short note provides a simple proof of the asymptotic distribution of Browne's (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) test statistic by using an equivalent form of the statistic that does not involve orthogonal component functions and consequently avoids all complicating issues associated with them.

  20. Comparison of small n statistical tests of differential expression applied to microarrays

    Directory of Open Access Journals (Sweden)

    Lee Anna Y

    2009-02-01

    Full Text Available Abstract Background DNA microarrays provide data for genome wide patterns of expression between observation classes. Microarray studies often have small samples sizes, however, due to cost constraints or specimen availability. This can lead to poor random error estimates and inaccurate statistical tests of differential expression. We compare the performance of the standard t-test, fold change, and four small n statistical test methods designed to circumvent these problems. We report results of various normalization methods for empirical microarray data and of various random error models for simulated data. Results Three Empirical Bayes methods (CyberT, BRB, and limma t-statistics were the most effective statistical tests across simulated and both 2-colour cDNA and Affymetrix experimental data. The CyberT regularized t-statistic in particular was able to maintain expected false positive rates with simulated data showing high variances at low gene intensities, although at the cost of low true positive rates. The Local Pooled Error (LPE test introduced a bias that lowered false positive rates below theoretically expected values and had lower power relative to the top performers. The standard two-sample t-test and fold change were also found to be sub-optimal for detecting differentially expressed genes. The generalized log transformation was shown to be beneficial in improving results with certain data sets, in particular high variance cDNA data. Conclusion Pre-processing of data influences performance and the proper combination of pre-processing and statistical testing is necessary for obtaining the best results. All three Empirical Bayes methods assessed in our study are good choices for statistical tests for small n microarray studies for both Affymetrix and cDNA data. Choice of method for a particular study will depend on software and normalization preferences.

  1. Beam wandering statistics of twin thin laser beam propagation under generalized atmospheric conditions.

    Science.gov (United States)

    Pérez, Darío G; Funes, Gustavo

    2012-12-03

    Under the Geometrics Optics approximation is possible to estimate the covariance between the displacements of two thin beams after they have propagated through a turbulent medium. Previous works have concentrated in long propagation distances to provide models for the wandering statistics. These models are useful when the separation between beams is smaller than the propagation path-regardless of the characteristics scales of the turbulence. In this work we give a complete model for these covariances, behavior introducing absolute limits to the validity of former approximations. Moreover, these generalizations are established for non-Kolmogorov atmospheric models.

  2. The use of test scores from large-scale assessment surveys: psychometric and statistical considerations

    Directory of Open Access Journals (Sweden)

    Henry Braun

    2017-11-01

    Full Text Available Abstract Background Economists are making increasing use of measures of student achievement obtained through large-scale survey assessments such as NAEP, TIMSS, and PISA. The construction of these measures, employing plausible value (PV methodology, is quite different from that of the more familiar test scores associated with assessments such as the SAT or ACT. These differences have important implications both for utilization and interpretation. Although much has been written about PVs, it appears that there are still misconceptions about whether and how to employ them in secondary analyses. Methods We address a range of technical issues, including those raised in a recent article that was written to inform economists using these databases. First, an extensive review of the relevant literature was conducted, with particular attention to key publications that describe the derivation and psychometric characteristics of such achievement measures. Second, a simulation study was carried out to compare the statistical properties of estimates based on the use of PVs with those based on other, commonly used methods. Results It is shown, through both theoretical analysis and simulation, that under fairly general conditions appropriate use of PV yields approximately unbiased estimates of model parameters in regression analyses of large scale survey data. The superiority of the PV methodology is particularly evident when measures of student achievement are employed as explanatory variables. Conclusions The PV methodology used to report student test performance in large scale surveys remains the state-of-the-art for secondary analyses of these databases.

  3. Study designs, use of statistical tests, and statistical analysis software choice in 2015: Results from two Pakistani monthly Medline indexed journals.

    Science.gov (United States)

    Shaikh, Masood Ali

    2017-09-01

    Assessment of research articles in terms of study designs used, statistical tests applied and the use of statistical analysis programmes help determine research activity profile and trends in the country. In this descriptive study, all original articles published by Journal of Pakistan Medical Association (JPMA) and Journal of the College of Physicians and Surgeons Pakistan (JCPSP), in the year 2015 were reviewed in terms of study designs used, application of statistical tests, and the use of statistical analysis programmes. JPMA and JCPSP published 192 and 128 original articles, respectively, in the year 2015. Results of this study indicate that cross-sectional study design, bivariate inferential statistical analysis entailing comparison between two variables/groups, and use of statistical software programme SPSS to be the most common study design, inferential statistical analysis, and statistical analysis software programmes, respectively. These results echo previously published assessment of these two journals for the year 2014.

  4. Computing Statistics under Interval and Fuzzy Uncertainty Applications to Computer Science and Engineering

    CERN Document Server

    Nguyen, Hung T; Wu, Berlin; Xiang, Gang

    2012-01-01

    In many practical situations, we are interested in statistics characterizing a population of objects: e.g. in the mean height of people from a certain area.   Most algorithms for estimating such statistics assume that the sample values are exact. In practice, sample values come from measurements, and measurements are never absolutely accurate. Sometimes, we know the exact probability distribution of the measurement inaccuracy, but often, we only know the upper bound on this inaccuracy. In this case, we have interval uncertainty: e.g. if the measured value is 1.0, and inaccuracy is bounded by 0.1, then the actual (unknown) value of the quantity can be anywhere between 1.0 - 0.1 = 0.9 and 1.0 + 0.1 = 1.1. In other cases, the values are expert estimates, and we only have fuzzy information about the estimation inaccuracy.   This book shows how to compute statistics under such interval and fuzzy uncertainty. The resulting methods are applied to computer science (optimal scheduling of different processors), to in...

  5. Evaluating Two Models of Collaborative Tests in an Online Introductory Statistics Course

    Science.gov (United States)

    Björnsdóttir, Auðbjörg; Garfield, Joan; Everson, Michelle

    2015-01-01

    This study explored the use of two different types of collaborative tests in an online introductory statistics course. A study was designed and carried out to investigate three research questions: (1) What is the difference in students' learning between using consensus and non-consensus collaborative tests in the online environment?, (2) What is…

  6. P-Value, a true test of statistical significance? a cautionary note ...

    African Journals Online (AJOL)

    While it's not the intention of the founders of significance testing and hypothesis testing to have the two ideas intertwined as if they are complementary, the inconvenient marriage of the two practices into one coherent, convenient, incontrovertible and misinterpreted practice has dotted our standard statistics textbooks and ...

  7. Transit timing observations from Kepler. VI. Potentially interesting candidate systems from fourier-based statistical tests

    DEFF Research Database (Denmark)

    Steffen, J.H.; Ford, E.B.; Rowe, J.F.

    2012-01-01

    We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through quarter six of science data. We conduct two statistical tests for all KOIs and a related statistical test for all pairs of KOIs in multi-transiting systems. These tests identify...... several systems which show potentially interesting transit timing variations (TTVs). Strong TTV systems have been valuable for the confirmation of planets and their mass measurements. Many of the systems identified in this study should prove fruitful for detailed TTV studies....

  8. TRANSIT TIMING OBSERVATIONS FROM KEPLER. VI. POTENTIALLY INTERESTING CANDIDATE SYSTEMS FROM FOURIER-BASED STATISTICAL TESTS

    International Nuclear Information System (INIS)

    Steffen, Jason H.; Ford, Eric B.; Rowe, Jason F.; Borucki, William J.; Bryson, Steve; Caldwell, Douglas A.; Jenkins, Jon M.; Koch, David G.; Sanderfer, Dwight T.; Seader, Shawn; Twicken, Joseph D.; Fabrycky, Daniel C.; Holman, Matthew J.; Welsh, William F.; Batalha, Natalie M.; Ciardi, David R.; Kjeldsen, Hans; Prša, Andrej

    2012-01-01

    We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through quarter six of science data. We conduct two statistical tests for all KOIs and a related statistical test for all pairs of KOIs in multi-transiting systems. These tests identify several systems which show potentially interesting transit timing variations (TTVs). Strong TTV systems have been valuable for the confirmation of planets and their mass measurements. Many of the systems identified in this study should prove fruitful for detailed TTV studies.

  9. Statistical alignment: computational properties, homology testing and goodness-of-fit

    DEFF Research Database (Denmark)

    Hein, J; Wiuf, Carsten; Møller, Martin

    2000-01-01

    The model of insertions and deletions in biological sequences, first formulated by Thorne, Kishino, and Felsenstein in 1991 (the TKF91 model), provides a basis for performing alignment within a statistical framework. Here we investigate this model.Firstly, we show how to accelerate the statistical...... alignment algorithms several orders of magnitude. The main innovations are to confine likelihood calculations to a band close to the similarity based alignment, to get good initial guesses of the evolutionary parameters and to apply an efficient numerical optimisation algorithm for finding the maximum...... analysis.Secondly, we propose a new homology test based on this model, where homology means that an ancestor to a sequence pair can be found finitely far back in time. This test has statistical advantages relative to the traditional shuffle test for proteins.Finally, we describe a goodness-of-fit test...

  10. Improved Test Planning and Analysis Through the Use of Advanced Statistical Methods

    Science.gov (United States)

    Green, Lawrence L.; Maxwell, Katherine A.; Glass, David E.; Vaughn, Wallace L.; Barger, Weston; Cook, Mylan

    2016-01-01

    The goal of this work is, through computational simulations, to provide statistically-based evidence to convince the testing community that a distributed testing approach is superior to a clustered testing approach for most situations. For clustered testing, numerous, repeated test points are acquired at a limited number of test conditions. For distributed testing, only one or a few test points are requested at many different conditions. The statistical techniques of Analysis of Variance (ANOVA), Design of Experiments (DOE) and Response Surface Methods (RSM) are applied to enable distributed test planning, data analysis and test augmentation. The D-Optimal class of DOE is used to plan an optimally efficient single- and multi-factor test. The resulting simulated test data are analyzed via ANOVA and a parametric model is constructed using RSM. Finally, ANOVA can be used to plan a second round of testing to augment the existing data set with new data points. The use of these techniques is demonstrated through several illustrative examples. To date, many thousands of comparisons have been performed and the results strongly support the conclusion that the distributed testing approach outperforms the clustered testing approach.

  11. Permutational distribution of the log-rank statistic under random censorship with applications to carcinogenicity assays.

    Science.gov (United States)

    Heimann, G; Neuhaus, G

    1998-03-01

    In the random censorship model, the log-rank test is often used for comparing a control group with different dose groups. If the number of tumors is small, so-called exact methods are often applied for computing critical values from a permutational distribution. Two of these exact methods are discussed and shown to be incorrect. The correct permutational distribution is derived and studied with respect to its behavior under unequal censoring in the light of recent results proving that the permutational version and the unconditional version of the log-rank test are asymptotically equivalent even under unequal censoring. The log-rank test is studied by simulations of a realistic scenario from a bioassay with small numbers of tumors.

  12. Testing University Rankings Statistically: Why this Perhaps is not such a Good Idea after All. Some Reflections on Statistical Power, Effect Size, Random Sampling and Imaginary Populations

    DEFF Research Database (Denmark)

    Schneider, Jesper Wiborg

    2012-01-01

    In this paper we discuss and question the use of statistical significance tests in relation to university rankings as recently suggested. We outline the assumptions behind and interpretations of statistical significance tests and relate this to examples from the recent SCImago Institutions Rankin...

  13. Properties of permutation-based gene tests and controlling type 1 error using a summary statistic based gene test.

    Science.gov (United States)

    Swanson, David M; Blacker, Deborah; Alchawa, Taofik; Ludwig, Kerstin U; Mangold, Elisabeth; Lange, Christoph

    2013-11-07

    The advent of genome-wide association studies has led to many novel disease-SNP associations, opening the door to focused study on their biological underpinnings. Because of the importance of analyzing these associations, numerous statistical methods have been devoted to them. However, fewer methods have attempted to associate entire genes or genomic regions with outcomes, which is potentially more useful knowledge from a biological perspective and those methods currently implemented are often permutation-based. One property of some permutation-based tests is that their power varies as a function of whether significant markers are in regions of linkage disequilibrium (LD) or not, which we show from a theoretical perspective. We therefore develop two methods for quantifying the degree of association between a genomic region and outcome, both of whose power does not vary as a function of LD structure. One method uses dimension reduction to "filter" redundant information when significant LD exists in the region, while the other, called the summary-statistic test, controls for LD by scaling marker Z-statistics using knowledge of the correlation matrix of markers. An advantage of this latter test is that it does not require the original data, but only their Z-statistics from univariate regressions and an estimate of the correlation structure of markers, and we show how to modify the test to protect the type 1 error rate when the correlation structure of markers is misspecified. We apply these methods to sequence data of oral cleft and compare our results to previously proposed gene tests, in particular permutation-based ones. We evaluate the versatility of the modification of the summary-statistic test since the specification of correlation structure between markers can be inaccurate. We find a significant association in the sequence data between the 8q24 region and oral cleft using our dimension reduction approach and a borderline significant association using the

  14. Price limits and stock market efficiency: Evidence from rolling bicorrelation test statistic

    International Nuclear Information System (INIS)

    Lim, Kian-Ping; Brooks, Robert D.

    2009-01-01

    Using the rolling bicorrelation test statistic, the present paper compares the efficiency of stock markets from China, Korea and Taiwan in selected sub-periods with different price limits regimes. The statistical results do not support the claims that restrictive price limits and price limits per se are jeopardizing market efficiency. However, the evidence does not imply that price limits have no effect on the price discovery process but rather suggesting that market efficiency is not merely determined by price limits.

  15. Tests and Confidence Intervals for an Extended Variance Component Using the Modified Likelihood Ratio Statistic

    DEFF Research Database (Denmark)

    Christensen, Ole Fredslund; Frydenberg, Morten; Jensen, Jens Ledet

    2005-01-01

    The large deviation modified likelihood ratio statistic is studied for testing a variance component equal to a specified value. Formulas are presented in the general balanced case, whereas in the unbalanced case only the one-way random effects model is studied. Simulation studies are presented......, showing that the normal approximation to the large deviation modified likelihood ratio statistic gives confidence intervals for variance components with coverage probabilities very close to the nominal confidence coefficient....

  16. A NEW TEST OF THE STATISTICAL NATURE OF THE BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Lin, Yen-Ting; Ostriker, Jeremiah P.; Miller, Christopher J.

    2010-01-01

    A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a 'statistical model' of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., L tot ∼> 4 x 10 11 h -2 70 L sun ) are unlikely (probability ≤3 x 10 -4 ) to be drawn from the LD defined by all red cluster galaxies more luminous than M r = -20. On the other hand, BCGs in less luminous clusters are consistent with being the statistical extreme. Applying our method to the second brightest galaxies, we show that they are consistent with being the statistical extreme, which implies that the BCGs are also distinct from non-BCG luminous, red, cluster galaxies. We point out some issues with the interpretation of the classical tests proposed by Tremaine and Richstone (TR) that are designed to examine the statistical nature of BCGs, investigate the robustness of both our statistical test and those of TR against difficulties in photometry of galaxies of large angular size, and discuss the implication of our findings on surveys that use the luminous red galaxies to measure the baryon acoustic oscillation features in the galaxy power spectrum.

  17. Statistical test data selection for reliability evalution of process computer software

    International Nuclear Information System (INIS)

    Volkmann, K.P.; Hoermann, H.; Ehrenberger, W.

    1976-01-01

    The paper presents a concept for converting knowledge about the characteristics of process states into practicable procedures for the statistical selection of test cases in testing process computer software. Process states are defined as vectors whose components consist of values of input variables lying in discrete positions or within given limits. Two approaches for test data selection, based on knowledge about cases of demand, are outlined referring to a purely probabilistic method and to the mathematics of stratified sampling. (orig.) [de

  18. Evaluating statistical tests on OLAP cubes to compare degree of disease.

    Science.gov (United States)

    Ordonez, Carlos; Chen, Zhibo

    2009-09-01

    Statistical tests represent an important technique used to formulate and validate hypotheses on a dataset. They are particularly useful in the medical domain, where hypotheses link disease with medical measurements, risk factors, and treatment. In this paper, we propose to compute parametric statistical tests treating patient records as elements in a multidimensional cube. We introduce a technique that combines dimension lattice traversal and statistical tests to discover significant differences in the degree of disease within pairs of patient groups. In order to understand a cause-effect relationship, we focus on patient group pairs differing in one dimension. We introduce several optimizations to prune the search space, to discover significant group pairs, and to summarize results. We present experiments showing important medical findings and evaluating scalability with medical datasets.

  19. An investigation of the statistical power of neutrality tests based on comparative and population genetic data

    DEFF Research Database (Denmark)

    Zhai, Weiwei; Nielsen, Rasmus; Slatkin, Montgomery

    2009-01-01

    In this report, we investigate the statistical power of several tests of selective neutrality based on patterns of genetic diversity within and between species. The goal is to compare tests based solely on population genetic data with tests using comparative data or a combination of comparative...... and population genetic data. We show that in the presence of repeated selective sweeps on relatively neutral background, tests based on the d(N)/d(S) ratios in comparative data almost always have more power to detect selection than tests based on population genetic data, even if the overall level of divergence...... selection. The Hudson-Kreitman-Aguadé test is the most powerful test for detecting positive selection among the population genetic tests investigated, whereas McDonald-Kreitman test typically has more power to detect negative selection. We discuss our findings in the light of the discordant results obtained...

  20. Operational statistical analysis of the results of computer-based testing of students

    Directory of Open Access Journals (Sweden)

    Виктор Иванович Нардюжев

    2018-12-01

    Full Text Available The article is devoted to the issues of statistical analysis of results of computer-based testing for evaluation of educational achievements of students. The issues are relevant due to the fact that computerbased testing in Russian universities has become an important method for evaluation of educational achievements of students and quality of modern educational process. Usage of modern methods and programs for statistical analysis of results of computer-based testing and assessment of quality of developed tests is an actual problem for every university teacher. The article shows how the authors solve this problem using their own program “StatInfo”. For several years the program has been successfully applied in a credit system of education at such technological stages as loading computerbased testing protocols into a database, formation of queries, generation of reports, lists, and matrices of answers for statistical analysis of quality of test items. Methodology, experience and some results of its usage by university teachers are described in the article. Related topics of a test development, models, algorithms, technologies, and software for large scale computer-based testing has been discussed by the authors in their previous publications which are presented in the reference list.

  1. Statistical properties of a utility measure of observer performance compared to area under the ROC curve

    Science.gov (United States)

    Abbey, Craig K.; Samuelson, Frank W.; Gallas, Brandon D.; Boone, John M.; Niklason, Loren T.

    2013-03-01

    The receiver operating characteristic (ROC) curve has become a common tool for evaluating diagnostic imaging technologies, and the primary endpoint of such evaluations is the area under the curve (AUC), which integrates sensitivity over the entire false positive range. An alternative figure of merit for ROC studies is expected utility (EU), which focuses on the relevant region of the ROC curve as defined by disease prevalence and the relative utility of the task. However if this measure is to be used, it must also have desirable statistical properties keep the burden of observer performance studies as low as possible. Here, we evaluate effect size and variability for EU and AUC. We use two observer performance studies recently submitted to the FDA to compare the EU and AUC endpoints. The studies were conducted using the multi-reader multi-case methodology in which all readers score all cases in all modalities. ROC curves from the study were used to generate both the AUC and EU values for each reader and modality. The EU measure was computed assuming an iso-utility slope of 1.03. We find mean effect sizes, the reader averaged difference between modalities, to be roughly 2.0 times as big for EU as AUC. The standard deviation across readers is roughly 1.4 times as large, suggesting better statistical properties for the EU endpoint. In a simple power analysis of paired comparison across readers, the utility measure required 36% fewer readers on average to achieve 80% statistical power compared to AUC.

  2. The extended statistical analysis of toxicity tests using standardised effect sizes (SESs): a comparison of nine published papers.

    Science.gov (United States)

    Festing, Michael F W

    2014-01-01

    The safety of chemicals, drugs, novel foods and genetically modified crops is often tested using repeat-dose sub-acute toxicity tests in rats or mice. It is important to avoid misinterpretations of the results as these tests are used to help determine safe exposure levels in humans. Treated and control groups are compared for a range of haematological, biochemical and other biomarkers which may indicate tissue damage or other adverse effects. However, the statistical analysis and presentation of such data poses problems due to the large number of statistical tests which are involved. Often, it is not clear whether a "statistically significant" effect is real or a false positive (type I error) due to sampling variation. The author's conclusions appear to be reached somewhat subjectively by the pattern of statistical significances, discounting those which they judge to be type I errors and ignoring any biomarker where the p-value is greater than p = 0.05. However, by using standardised effect sizes (SESs) a range of graphical methods and an over-all assessment of the mean absolute response can be made. The approach is an extension, not a replacement of existing methods. It is intended to assist toxicologists and regulators in the interpretation of the results. Here, the SES analysis has been applied to data from nine published sub-acute toxicity tests in order to compare the findings with those of the author's. Line plots, box plots and bar plots show the pattern of response. Dose-response relationships are easily seen. A "bootstrap" test compares the mean absolute differences across dose groups. In four out of seven papers where the no observed adverse effect level (NOAEL) was estimated by the authors, it was set too high according to the bootstrap test, suggesting that possible toxicity is under-estimated.

  3. The extended statistical analysis of toxicity tests using standardised effect sizes (SESs: a comparison of nine published papers.

    Directory of Open Access Journals (Sweden)

    Michael F W Festing

    Full Text Available The safety of chemicals, drugs, novel foods and genetically modified crops is often tested using repeat-dose sub-acute toxicity tests in rats or mice. It is important to avoid misinterpretations of the results as these tests are used to help determine safe exposure levels in humans. Treated and control groups are compared for a range of haematological, biochemical and other biomarkers which may indicate tissue damage or other adverse effects. However, the statistical analysis and presentation of such data poses problems due to the large number of statistical tests which are involved. Often, it is not clear whether a "statistically significant" effect is real or a false positive (type I error due to sampling variation. The author's conclusions appear to be reached somewhat subjectively by the pattern of statistical significances, discounting those which they judge to be type I errors and ignoring any biomarker where the p-value is greater than p = 0.05. However, by using standardised effect sizes (SESs a range of graphical methods and an over-all assessment of the mean absolute response can be made. The approach is an extension, not a replacement of existing methods. It is intended to assist toxicologists and regulators in the interpretation of the results. Here, the SES analysis has been applied to data from nine published sub-acute toxicity tests in order to compare the findings with those of the author's. Line plots, box plots and bar plots show the pattern of response. Dose-response relationships are easily seen. A "bootstrap" test compares the mean absolute differences across dose groups. In four out of seven papers where the no observed adverse effect level (NOAEL was estimated by the authors, it was set too high according to the bootstrap test, suggesting that possible toxicity is under-estimated.

  4. Classification of Underlying Causes of Power Quality Disturbances: Deterministic versus Statistical Methods

    Directory of Open Access Journals (Sweden)

    Emmanouil Styvaktakis

    2007-01-01

    Full Text Available This paper presents the two main types of classification methods for power quality disturbances based on underlying causes: deterministic classification, giving an expert system as an example, and statistical classification, with support vector machines (a novel method as an example. An expert system is suitable when one has limited amount of data and sufficient power system expert knowledge; however, its application requires a set of threshold values. Statistical methods are suitable when large amount of data is available for training. Two important issues to guarantee the effectiveness of a classifier, data segmentation, and feature extraction are discussed. Segmentation of a sequence of data recording is preprocessing to partition the data into segments each representing a duration containing either an event or a transition between two events. Extraction of features is applied to each segment individually. Some useful features and their effectiveness are then discussed. Some experimental results are included for demonstrating the effectiveness of both systems. Finally, conclusions are given together with the discussion of some future research directions.

  5. Statistical modelling of grapevine yield in the Port Wine region under present and future climate conditions

    Science.gov (United States)

    Santos, João A.; Malheiro, Aureliano C.; Karremann, Melanie K.; Pinto, Joaquim G.

    2011-03-01

    The impact of projected climate change on wine production was analysed for the Demarcated Region of Douro, Portugal. A statistical grapevine yield model (GYM) was developed using climate parameters as predictors. Statistically significant correlations were identified between annual yield and monthly mean temperatures and monthly precipitation totals during the growing cycle. These atmospheric factors control grapevine yield in the region, with the GYM explaining 50.4% of the total variance in the yield time series in recent decades. Anomalously high March rainfall (during budburst, shoot and inflorescence development) favours yield, as well as anomalously high temperatures and low precipitation amounts in May and June (May: flowering and June: berry development). The GYM was applied to a regional climate model output, which was shown to realistically reproduce the GYM predictors. Finally, using ensemble simulations under the A1B emission scenario, projections for GYM-derived yield in the Douro Region, and for the whole of the twenty-first century, were analysed. A slight upward trend in yield is projected to occur until about 2050, followed by a steep and continuous increase until the end of the twenty-first century, when yield is projected to be about 800 kg/ha above current values. While this estimate is based on meteorological parameters alone, changes due to elevated CO2 may further enhance this effect. In spite of the associated uncertainties, it can be stated that projected climate change may significantly benefit wine yield in the Douro Valley.

  6. Outcomes Definitions and Statistical Tests in Oncology Studies: A Systematic Review of the Reporting Consistency.

    Science.gov (United States)

    Rivoirard, Romain; Duplay, Vianney; Oriol, Mathieu; Tinquaut, Fabien; Chauvin, Franck; Magne, Nicolas; Bourmaud, Aurelie

    2016-01-01

    Quality of reporting for Randomized Clinical Trials (RCTs) in oncology was analyzed in several systematic reviews, but, in this setting, there is paucity of data for the outcomes definitions and consistency of reporting for statistical tests in RCTs and Observational Studies (OBS). The objective of this review was to describe those two reporting aspects, for OBS and RCTs in oncology. From a list of 19 medical journals, three were retained for analysis, after a random selection: British Medical Journal (BMJ), Annals of Oncology (AoO) and British Journal of Cancer (BJC). All original articles published between March 2009 and March 2014 were screened. Only studies whose main outcome was accompanied by a corresponding statistical test were included in the analysis. Studies based on censored data were excluded. Primary outcome was to assess quality of reporting for description of primary outcome measure in RCTs and of variables of interest in OBS. A logistic regression was performed to identify covariates of studies potentially associated with concordance of tests between Methods and Results parts. 826 studies were included in the review, and 698 were OBS. Variables were described in Methods section for all OBS studies and primary endpoint was clearly detailed in Methods section for 109 RCTs (85.2%). 295 OBS (42.2%) and 43 RCTs (33.6%) had perfect agreement for reported statistical test between Methods and Results parts. In multivariable analysis, variable "number of included patients in study" was associated with test consistency: aOR (adjusted Odds Ratio) for third group compared to first group was equal to: aOR Grp3 = 0.52 [0.31-0.89] (P value = 0.009). Variables in OBS and primary endpoint in RCTs are reported and described with a high frequency. However, statistical tests consistency between methods and Results sections of OBS is not always noted. Therefore, we encourage authors and peer reviewers to verify consistency of statistical tests in oncology studies.

  7. Test Marketing Exemption (TME) for New Chemical Review under TSCA

    Science.gov (United States)

    Under section 5 of TSCA, EPA established an exemption for certain chemicals that are manufactured (including imported) for test marketing. You can learn more here about the requirements of this exemption, along with the review and submission process.

  8. The testing-effect under investigation. Experiences in Kiel

    NARCIS (Netherlands)

    Dirkx, Kim; Kester, Liesbeth; Kirschner, Paul A.

    2013-01-01

    Dirkx, K. J. H., Kester, L., & Kirschner, P. A. (2013, 22 January). The testing-effect under investigation. Experiences in Kiel. Presentation held at the Learning & Cognition meeting, Heerlen, The Netherlands.

  9. Superconductors for fusion magnets tested under pulsed field in SULTAN

    International Nuclear Information System (INIS)

    Bruzzone, P.; Bottura, L.; Katheder, H.; Blau, B.; Rohleder, I.; Vecsey, G.

    1995-01-01

    The SULTAN III test facility has been upgraded with a pair of pulsed field coils to carry out AC losses and stability experiments under full operating loads on large size, fusion conductors for ITER. A fast data aquisition system records the conductor behaviour under fast field transient. The commissioning results of the pulsed coils and instrumentation are critically discussed and the test capability of the set up is assessed. (orig.)

  10. Testing independence of bivariate interval-censored data using modified Kendall's tau statistic.

    Science.gov (United States)

    Kim, Yuneung; Lim, Johan; Park, DoHwan

    2015-11-01

    In this paper, we study a nonparametric procedure to test independence of bivariate interval censored data; for both current status data (case 1 interval-censored data) and case 2 interval-censored data. To do it, we propose a score-based modification of the Kendall's tau statistic for bivariate interval-censored data. Our modification defines the Kendall's tau statistic with expected numbers of concordant and disconcordant pairs of data. The performance of the modified approach is illustrated by simulation studies and application to the AIDS study. We compare our method to alternative approaches such as the two-stage estimation method by Sun et al. (Scandinavian Journal of Statistics, 2006) and the multiple imputation method by Betensky and Finkelstein (Statistics in Medicine, 1999b). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Efficient statistical tests to compare Youden index: accounting for contingency correlation.

    Science.gov (United States)

    Chen, Fangyao; Xue, Yuqiang; Tan, Ming T; Chen, Pingyan

    2015-04-30

    Youden index is widely utilized in studies evaluating accuracy of diagnostic tests and performance of predictive, prognostic, or risk models. However, both one and two independent sample tests on Youden index have been derived ignoring the dependence (association) between sensitivity and specificity, resulting in potentially misleading findings. Besides, paired sample test on Youden index is currently unavailable. This article develops efficient statistical inference procedures for one sample, independent, and paired sample tests on Youden index by accounting for contingency correlation, namely associations between sensitivity and specificity and paired samples typically represented in contingency tables. For one and two independent sample tests, the variances are estimated by Delta method, and the statistical inference is based on the central limit theory, which are then verified by bootstrap estimates. For paired samples test, we show that the estimated covariance of the two sensitivities and specificities can be represented as a function of kappa statistic so the test can be readily carried out. We then show the remarkable accuracy of the estimated variance using a constrained optimization approach. Simulation is performed to evaluate the statistical properties of the derived tests. The proposed approaches yield more stable type I errors at the nominal level and substantially higher power (efficiency) than does the original Youden's approach. Therefore, the simple explicit large sample solution performs very well. Because we can readily implement the asymptotic and exact bootstrap computation with common software like R, the method is broadly applicable to the evaluation of diagnostic tests and model performance. Copyright © 2015 John Wiley & Sons, Ltd.

  12. The acid solubility test of clay mineral under microwave

    International Nuclear Information System (INIS)

    Zheng Ying; Niu Yuqing; Wu Peisheng; Niu Xuejun

    2001-01-01

    The acid solubility test of Al 3+ in clay from some uranium ores under microwave is introduced. The result shows that the concentration of Al 3+ in solution and the acid consumption increase rapidly under microwave comparing with normal leaching condition. It is infeasible to adopt microwave slacking method for intensively leaching uranium from uranium ore containing more clay

  13. Beyond P Values and Hypothesis Testing: Using the Minimum Bayes Factor to Teach Statistical Inference in Undergraduate Introductory Statistics Courses

    Science.gov (United States)

    Page, Robert; Satake, Eiki

    2017-01-01

    While interest in Bayesian statistics has been growing in statistics education, the treatment of the topic is still inadequate in both textbooks and the classroom. Because so many fields of study lead to careers that involve a decision-making process requiring an understanding of Bayesian methods, it is becoming increasingly clear that Bayesian…

  14. IEEE Std 101-1987: IEEE guide for the statistical analysis of thermal life test data

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This revision of IEEE Std 101-1972 describes statistical analyses for data from thermally accelerated aging tests. It explains the basis and use of statistical calculations for an engineer or scientist. Accelerated test procedures usually call for a number of specimens to be aged at each of several temperatures appreciably above normal operating temperatures. High temperatures are chosen to produce specimen failures (according to specified failure criteria) in typically one week to one year. The test objective is to determine the dependence of median life on temperature from the data, and to estimate, by extrapolation, the median life to be expected at service temperature. This guide presents methods for analyzing such data and for comparing test data on different materials

  15. A general statistical test for correlations in a finite-length time series.

    Science.gov (United States)

    Hanson, Jeffery A; Yang, Haw

    2008-06-07

    The statistical properties of the autocorrelation function from a time series composed of independently and identically distributed stochastic variables has been studied. Analytical expressions for the autocorrelation function's variance have been derived. It has been found that two common ways of calculating the autocorrelation, moving-average and Fourier transform, exhibit different uncertainty characteristics. For periodic time series, the Fourier transform method is preferred because it gives smaller uncertainties that are uniform through all time lags. Based on these analytical results, a statistically robust method has been proposed to test the existence of correlations in a time series. The statistical test is verified by computer simulations and an application to single-molecule fluorescence spectroscopy is discussed.

  16. Statistical tests for the Gaussian nature of primordial fluctuations through CBR experiments

    International Nuclear Information System (INIS)

    Luo, X.

    1994-01-01

    Information about the physical processes that generate the primordial fluctuations in the early Universe can be gained by testing the Gaussian nature of the fluctuations through cosmic microwave background radiation (CBR) temperature anisotropy experiments. One of the crucial aspects of density perturbations that are produced by the standard inflation scenario is that they are Gaussian, whereas seeds produced by topological defects left over from an early cosmic phase transition tend to be non-Gaussian. To carry out this test, sophisticated statistical tools are required. In this paper, we will discuss several such statistical tools, including multivariant skewness and kurtosis, Euler-Poincare characteristics, the three-point temperature correlation function, and Hotelling's T 2 statistic defined through bispectral estimates of a one-dimensional data set. The effect of noise present in the current data is discussed in detail and the COBE 53 GHz data set is analyzed. Our analysis shows that, on the large angular scale to which COBE is sensitive, the statistics are probably Gaussian. On the small angular scales, the importance of Hotelling's T 2 statistic is stressed, and the minimum sample size required to test Gaussianity is estimated. Although the current data set available from various experiments at half-degree scales is still too small, improvement of the data set by roughly a factor of 2 will be enough to test the Gaussianity statistically. On the arc min scale, we analyze the recent RING data through bispectral analysis, and the result indicates possible deviation from Gaussianity. Effects of point sources are also discussed. It is pointed out that the Gaussianity problem can be resolved in the near future by ground-based or balloon-borne experiments

  17. A test statistic in the complex Wishart distribution and its application to change detection in polarimetric SAR data

    DEFF Research Database (Denmark)

    Conradsen, Knut; Nielsen, Allan Aasbjerg; Schou, Jesper

    2003-01-01

    . Based on this distribution, a test statistic for equality of two such matrices and an associated asymptotic probability for obtaining a smaller value of the test statistic are derived and applied successfully to change detection in polarimetric SAR data. In a case study, EMISAR L-band data from April 17...... to HH, VV, or HV data alone, the derived test statistic reduces to the well-known gamma likelihood-ratio test statistic. The derived test statistic and the associated significance value can be applied as a line or edge detector in fully polarimetric SAR data also....

  18. Application of statistical methods to the testing of nuclear counting assemblies

    International Nuclear Information System (INIS)

    Gilbert, J.P.; Friedling, G.

    1965-01-01

    This report describes the application of the hypothesis test theory to the control of the 'statistical purity' and of the stability of the counting batteries used for measurements on activation detectors in research reactors. The principles involved and the experimental results obtained at Cadarache on batteries operating with the reactors PEGGY and AZUR are given. (authors) [fr

  19. Interpreting Statistical Significance Test Results: A Proposed New "What If" Method.

    Science.gov (United States)

    Kieffer, Kevin M.; Thompson, Bruce

    As the 1994 publication manual of the American Psychological Association emphasized, "p" values are affected by sample size. As a result, it can be helpful to interpret the results of statistical significant tests in a sample size context by conducting so-called "what if" analyses. However, these methods can be inaccurate…

  20. Recent Literature on Whether Statistical Significance Tests Should or Should Not Be Banned.

    Science.gov (United States)

    Deegear, James

    This paper summarizes the literature regarding statistical significant testing with an emphasis on recent literature in various discipline and literature exploring why researchers have demonstrably failed to be influenced by the American Psychological Association publication manual's encouragement to report effect sizes. Also considered are…

  1. Statistical Methods for the detection of answer copying on achievement tests

    NARCIS (Netherlands)

    Sotaridona, Leonardo

    2003-01-01

    This thesis contains a collection of studies where statistical methods for the detection of answer copying on achievement tests in multiple-choice format are proposed and investigated. Although all methods are suited to detect answer copying, each method is designed to address specific

  2. Pivotal statistics for testing subsets of structural parameters in the IV Regression Model

    NARCIS (Netherlands)

    Kleibergen, F.R.

    2000-01-01

    We construct a novel statistic to test hypothezes on subsets of the structural parameters in anInstrumental Variables (IV) regression model. We derive the chi squared limiting distribution of thestatistic and show that it has a degrees of freedom parameter that is equal to the number ofstructural

  3. A Critique of One-Tailed Hypothesis Test Procedures in Business and Economics Statistics Textbooks.

    Science.gov (United States)

    Liu, Tung; Stone, Courtenay C.

    1999-01-01

    Surveys introductory business and economics statistics textbooks and finds that they differ over the best way to explain one-tailed hypothesis tests: the simple null-hypothesis approach or the composite null-hypothesis approach. Argues that the composite null-hypothesis approach contains methodological shortcomings that make it more difficult for…

  4. A Comparison of Several Statistical Tests of Reciprocity of Self-Disclosure.

    Science.gov (United States)

    Dindia, Kathryn

    1988-01-01

    Reports the results of a study that used several statistical tests of reciprocity of self-disclosure. Finds little evidence for reciprocity of self-disclosure, and concludes that either reciprocity is an illusion, or that different or more sophisticated methods are needed to detect it. (MS)

  5. Statistical Requirements For Pass-Fail Testing Of Contraband Detection Systems

    International Nuclear Information System (INIS)

    Gilliam, David M.

    2011-01-01

    Contraband detection systems for homeland security applications are typically tested for probability of detection (PD) and probability of false alarm (PFA) using pass-fail testing protocols. Test protocols usually require specified values for PD and PFA to be demonstrated at a specified level of statistical confidence CL. Based on a recent more theoretical treatment of this subject [1], this summary reviews the definition of CL and provides formulas and spreadsheet functions for constructing tables of general test requirements and for determining the minimum number of tests required. The formulas and tables in this article may be generally applied to many other applications of pass-fail testing, in addition to testing of contraband detection systems.

  6. Testing statistical self-similarity in the topology of river networks

    Science.gov (United States)

    Troutman, Brent M.; Mantilla, Ricardo; Gupta, Vijay K.

    2010-01-01

    Recent work has demonstrated that the topological properties of real river networks deviate significantly from predictions of Shreve's random model. At the same time the property of mean self-similarity postulated by Tokunaga's model is well supported by data. Recently, a new class of network model called random self-similar networks (RSN) that combines self-similarity and randomness has been introduced to replicate important topological features observed in real river networks. We investigate if the hypothesis of statistical self-similarity in the RSN model is supported by data on a set of 30 basins located across the continental United States that encompass a wide range of hydroclimatic variability. We demonstrate that the generators of the RSN model obey a geometric distribution, and self-similarity holds in a statistical sense in 26 of these 30 basins. The parameters describing the distribution of interior and exterior generators are tested to be statistically different and the difference is shown to produce the well-known Hack's law. The inter-basin variability of RSN parameters is found to be statistically significant. We also test generator dependence on two climatic indices, mean annual precipitation and radiative index of dryness. Some indication of climatic influence on the generators is detected, but this influence is not statistically significant with the sample size available. Finally, two key applications of the RSN model to hydrology and geomorphology are briefly discussed.

  7. Toward the detection of gravitational waves under non-Gaussian noises I. Locally optimal statistic.

    Science.gov (United States)

    Yokoyama, Jun'ichi

    2014-01-01

    After reviewing the standard hypothesis test and the matched filter technique to identify gravitational waves under Gaussian noises, we introduce two methods to deal with non-Gaussian stationary noises. We formulate the likelihood ratio function under weakly non-Gaussian noises through the Edgeworth expansion and strongly non-Gaussian noises in terms of a new method we call Gaussian mapping where the observed marginal distribution and the two-body correlation function are fully taken into account. We then apply these two approaches to Student's t-distribution which has a larger tails than Gaussian. It is shown that while both methods work well in the case the non-Gaussianity is small, only the latter method works well for highly non-Gaussian case.

  8. Probabilistic risk assessment framework for structural systems under multiple hazards using Bayesian statistics

    International Nuclear Information System (INIS)

    Kwag, Shinyoung; Gupta, Abhinav

    2017-01-01

    Highlights: • This study presents the development of Bayesian framework for probabilistic risk assessment (PRA) of structural systems under multiple hazards. • The concepts of Bayesian network and Bayesian inference are combined by mapping the traditionally used fault trees into a Bayesian network. • The proposed mapping allows for consideration of dependencies as well as correlations between events. • Incorporation of Bayesian inference permits a novel way for exploration of a scenario that is likely to result in a system level “vulnerability.” - Abstract: Conventional probabilistic risk assessment (PRA) methodologies (USNRC, 1983; IAEA, 1992; EPRI, 1994; Ellingwood, 2001) conduct risk assessment for different external hazards by considering each hazard separately and independent of each other. The risk metric for a specific hazard is evaluated by a convolution of the fragility and the hazard curves. The fragility curve for basic event is obtained by using empirical, experimental, and/or numerical simulation data for a particular hazard. Treating each hazard as an independently can be inappropriate in some cases as certain hazards are statistically correlated or dependent. Examples of such correlated events include but are not limited to flooding induced fire, seismically induced internal or external flooding, or even seismically induced fire. In the current practice, system level risk and consequence sequences are typically calculated using logic trees to express the causative relationship between events. In this paper, we present the results from a study on multi-hazard risk assessment that is conducted using a Bayesian network (BN) with Bayesian inference. The framework can consider statistical dependencies among risks from multiple hazards, allows updating by considering the newly available data/information at any level, and provide a novel way to explore alternative failure scenarios that may exist due to vulnerabilities.

  9. Probabilistic risk assessment framework for structural systems under multiple hazards using Bayesian statistics

    Energy Technology Data Exchange (ETDEWEB)

    Kwag, Shinyoung [North Carolina State University, Raleigh, NC 27695 (United States); Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Gupta, Abhinav, E-mail: agupta1@ncsu.edu [North Carolina State University, Raleigh, NC 27695 (United States)

    2017-04-15

    Highlights: • This study presents the development of Bayesian framework for probabilistic risk assessment (PRA) of structural systems under multiple hazards. • The concepts of Bayesian network and Bayesian inference are combined by mapping the traditionally used fault trees into a Bayesian network. • The proposed mapping allows for consideration of dependencies as well as correlations between events. • Incorporation of Bayesian inference permits a novel way for exploration of a scenario that is likely to result in a system level “vulnerability.” - Abstract: Conventional probabilistic risk assessment (PRA) methodologies (USNRC, 1983; IAEA, 1992; EPRI, 1994; Ellingwood, 2001) conduct risk assessment for different external hazards by considering each hazard separately and independent of each other. The risk metric for a specific hazard is evaluated by a convolution of the fragility and the hazard curves. The fragility curve for basic event is obtained by using empirical, experimental, and/or numerical simulation data for a particular hazard. Treating each hazard as an independently can be inappropriate in some cases as certain hazards are statistically correlated or dependent. Examples of such correlated events include but are not limited to flooding induced fire, seismically induced internal or external flooding, or even seismically induced fire. In the current practice, system level risk and consequence sequences are typically calculated using logic trees to express the causative relationship between events. In this paper, we present the results from a study on multi-hazard risk assessment that is conducted using a Bayesian network (BN) with Bayesian inference. The framework can consider statistical dependencies among risks from multiple hazards, allows updating by considering the newly available data/information at any level, and provide a novel way to explore alternative failure scenarios that may exist due to vulnerabilities.

  10. Assessment of the beryllium lymphocyte proliferation test using statistical process control.

    Science.gov (United States)

    Cher, Daniel J; Deubner, David C; Kelsh, Michael A; Chapman, Pamela S; Ray, Rose M

    2006-10-01

    Despite more than 20 years of surveillance and epidemiologic studies using the beryllium blood lymphocyte proliferation test (BeBLPT) as a measure of beryllium sensitization (BeS) and as an aid for diagnosing subclinical chronic beryllium disease (CBD), improvements in specific understanding of the inhalation toxicology of CBD have been limited. Although epidemiologic data suggest that BeS and CBD risks vary by process/work activity, it has proven difficult to reach specific conclusions regarding the dose-response relationship between workplace beryllium exposure and BeS or subclinical CBD. One possible reason for this uncertainty could be misclassification of BeS resulting from variation in BeBLPT testing performance. The reliability of the BeBLPT, a biological assay that measures beryllium sensitization, is unknown. To assess the performance of four laboratories that conducted this test, we used data from a medical surveillance program that offered testing for beryllium sensitization with the BeBLPT. The study population was workers exposed to beryllium at various facilities over a 10-year period (1992-2001). Workers with abnormal results were offered diagnostic workups for CBD. Our analyses used a standard statistical technique, statistical process control (SPC), to evaluate test reliability. The study design involved a repeated measures analysis of BeBLPT results generated from the company-wide, longitudinal testing. Analytical methods included use of (1) statistical process control charts that examined temporal patterns of variation for the stimulation index, a measure of cell reactivity to beryllium; (2) correlation analysis that compared prior perceptions of BeBLPT instability to the statistical measures of test variation; and (3) assessment of the variation in the proportion of missing test results and how time periods with more missing data influenced SPC findings. During the period of this study, all laboratories displayed variation in test results that

  11. Hotspot detection using space-time scan statistics on children under five years of age in Depok

    Science.gov (United States)

    Verdiana, Miranti; Widyaningsih, Yekti

    2017-03-01

    Some problems that affect the health level in Depok is the high malnutrition rates from year to year and the more spread infectious and non-communicable diseases in some areas. Children under five years old is a vulnerable part of population to get the malnutrition and diseases. Based on this reason, it is important to observe the location and time, where and when, malnutrition in Depok happened in high intensity. To obtain the location and time of the hotspots of malnutrition and diseases that attack children under five years old, space-time scan statistics method can be used. Space-time scan statistic is a hotspot detection method, where the area and time of information and time are taken into account simultaneously in detecting the hotspots. This method detects a hotspot with a cylindrical scanning window: the cylindrical pedestal describes the area, and the height of cylinder describe the time. Cylinders formed is a hotspot candidate that may occur, which require testing of hypotheses, whether a cylinder can be summed up as a hotspot. Hotspot detection in this study carried out by forming a combination of several variables. Some combination of variables provides hotspot detection results that tend to be the same, so as to form groups (clusters). In the case of infant health level in Depok city, Beji health care center region in 2011-2012 is a hotspot. According to the combination of the variables used in the detection of hotspots, Beji health care center is most frequently as a hotspot. Hopefully the local government can take the right policy to improve the health level of children under five in the city of Depok.

  12. Failure-censored accelerated life test sampling plans for Weibull distribution under expected test time constraint

    International Nuclear Information System (INIS)

    Bai, D.S.; Chun, Y.R.; Kim, J.G.

    1995-01-01

    This paper considers the design of life-test sampling plans based on failure-censored accelerated life tests. The lifetime distribution of products is assumed to be Weibull with a scale parameter that is a log linear function of a (possibly transformed) stress. Two levels of stress higher than the use condition stress, high and low, are used. Sampling plans with equal expected test times at high and low test stresses which satisfy the producer's and consumer's risk requirements and minimize the asymptotic variance of the test statistic used to decide lot acceptability are obtained. The properties of the proposed life-test sampling plans are investigated

  13. Near-exact distributions for the block equicorrelation and equivariance likelihood ratio test statistic

    Science.gov (United States)

    Coelho, Carlos A.; Marques, Filipe J.

    2013-09-01

    In this paper the authors combine the equicorrelation and equivariance test introduced by Wilks [13] with the likelihood ratio test (l.r.t.) for independence of groups of variables to obtain the l.r.t. of block equicorrelation and equivariance. This test or its single block version may find applications in many areas as in psychology, education, medicine, genetics and they are important "in many tests of multivariate analysis, e.g. in MANOVA, Profile Analysis, Growth Curve analysis, etc" [12, 9]. By decomposing the overall hypothesis into the hypotheses of independence of groups of variables and the hypothesis of equicorrelation and equivariance we are able to obtain the expressions for the overall l.r.t. statistic and its moments. From these we obtain a suitable factorization of the characteristic function (c.f.) of the logarithm of the l.r.t. statistic, which enables us to develop highly manageable and precise near-exact distributions for the test statistic.

  14. Determination of Geometrical REVs Based on Volumetric Fracture Intensity and Statistical Tests

    Directory of Open Access Journals (Sweden)

    Ying Liu

    2018-05-01

    Full Text Available This paper presents a method to estimate a representative element volume (REV of a fractured rock mass based on the volumetric fracture intensity P32 and statistical tests. A 150 m × 80 m × 50 m 3D fracture network model was generated based on field data collected at the Maji dam site by using the rectangular window sampling method. The volumetric fracture intensity P32 of each cube was calculated by varying the cube location in the generated 3D fracture network model and varying the cube side length from 1 to 20 m, and the distribution of the P32 values was described. The size effect and spatial effect of the fractured rock mass were studied; the P32 values from the same cube sizes and different locations were significantly different, and the fluctuation in P32 values clearly decreases as the cube side length increases. In this paper, a new method that comprehensively considers the anisotropy of rock masses, simplicity of calculation and differences between different methods was proposed to estimate the geometrical REV size. The geometrical REV size of the fractured rock mass was determined based on the volumetric fracture intensity P32 and two statistical test methods, namely, the likelihood ratio test and the Wald–Wolfowitz runs test. The results of the two statistical tests were substantially different; critical cube sizes of 13 m and 12 m were estimated by the Wald–Wolfowitz runs test and the likelihood ratio test, respectively. Because the different test methods emphasize different considerations and impact factors, considering a result that these two tests accept, the larger cube size, 13 m, was selected as the geometrical REV size of the fractured rock mass at the Maji dam site in China.

  15. Statistical power analysis a simple and general model for traditional and modern hypothesis tests

    CERN Document Server

    Murphy, Kevin R; Wolach, Allen

    2014-01-01

    Noted for its accessible approach, this text applies the latest approaches of power analysis to both null hypothesis and minimum-effect testing using the same basic unified model. Through the use of a few simple procedures and examples, the authors show readers with little expertise in statistical analysis how to obtain the values needed to carry out the power analysis for their research. Illustrations of how these analyses work and how they can be used to choose the appropriate criterion for defining statistically significant outcomes are sprinkled throughout. The book presents a simple and g

  16. Precipitation projections under GCMs perspective and Turkish Water Foundation (TWF) statistical downscaling model procedures

    Science.gov (United States)

    Dabanlı, İsmail; Şen, Zekai

    2018-04-01

    The statistical climate downscaling model by the Turkish Water Foundation (TWF) is further developed and applied to a set of monthly precipitation records. The model is structured by two phases as spatial (regional) and temporal downscaling of global circulation model (GCM) scenarios. The TWF model takes into consideration the regional dependence function (RDF) for spatial structure and Markov whitening process (MWP) for temporal characteristics of the records to set projections. The impact of climate change on monthly precipitations is studied by downscaling Intergovernmental Panel on Climate Change-Special Report on Emission Scenarios (IPCC-SRES) A2 and B2 emission scenarios from Max Plank Institute (EH40PYC) and Hadley Center (HadCM3). The main purposes are to explain the TWF statistical climate downscaling model procedures and to expose the validation tests, which are rewarded in same specifications as "very good" for all stations except one (Suhut) station in the Akarcay basin that is in the west central part of Turkey. Eventhough, the validation score is just a bit lower at the Suhut station, the results are "satisfactory." It is, therefore, possible to say that the TWF model has reasonably acceptable skill for highly accurate estimation regarding standard deviation ratio (SDR), Nash-Sutcliffe efficiency (NSE), and percent bias (PBIAS) criteria. Based on the validated model, precipitation predictions are generated from 2011 to 2100 by using 30-year reference observation period (1981-2010). Precipitation arithmetic average and standard deviation have less than 5% error for EH40PYC and HadCM3 SRES (A2 and B2) scenarios.

  17. Reliability analysis of structures under periodic proof tests in service

    Science.gov (United States)

    Yang, J.-N.

    1976-01-01

    A reliability analysis of structures subjected to random service loads and periodic proof tests treats gust loads and maneuver loads as random processes. Crack initiation, crack propagation, and strength degradation are treated as the fatigue process. The time to fatigue crack initiation and ultimate strength are random variables. Residual strength decreases during crack propagation, so that failure rate increases with time. When a structure fails under periodic proof testing, a new structure is built and proof-tested. The probability of structural failure in service is derived from treatment of all the random variables, strength degradations, service loads, proof tests, and the renewal of failed structures. Some numerical examples are worked out.

  18. Spatial statistical analysis of basal stem root disease under natural field epidemic of oil palm

    Science.gov (United States)

    Kamu, Assis; Phin, Chong Khim; Seman, Idris Abu; Wan, Hoong Hak; Mun, Ho Chong

    2015-02-01

    Oil palm or scientifically known as Elaeis guineensis Jacq. is the most important commodity crop in Malaysia and has greatly contributed to the economy growth of the country. As far as disease is concerned in the industry, Basal Stem Rot (BSR) caused by Ganoderma boninence remains the most important disease. BSR disease is the most widely studied with information available for oil palm disease in Malaysia. However, there is still limited study on the spatial as well as temporal pattern or distribution of the disease especially under natural field epidemic condition in oil palm plantation. The objective of this study is to spatially identify the pattern of BSR disease under natural field epidemic using two geospatial analytical techniques, which are quadrat analysis for the first order properties of partial pattern analysis and nearest-neighbor analysis (NNA) for the second order properties of partial pattern analysis. Two study sites were selected with different age of tree. Both sites are located in Tawau, Sabah and managed by the same company. The results showed that at least one of the point pattern analysis used which is NNA (i.e. the second order properties of partial pattern analysis) has confirmed the disease is complete spatial randomness. This suggests the spread of the disease is not from tree to tree and the age of palm does not play a significance role in determining the spatial pattern of the disease. From the spatial pattern of the disease, it would help in the disease management program and for the industry in the future. The statistical modelling is expected to help in identifying the right model to estimate the yield loss of oil palm due to BSR disease in the future.

  19. Statistical Modeling for Quality Assurance of Human Papillomavirus DNA Batch Testing.

    Science.gov (United States)

    Beylerian, Emily N; Slavkovsky, Rose C; Holme, Francesca M; Jeronimo, Jose A

    2018-03-22

    Our objective was to simulate the distribution of human papillomavirus (HPV) DNA test results from a 96-well microplate assay to identify results that may be consistent with well-to-well contamination, enabling programs to apply specific quality assurance parameters. For this modeling study, we designed an algorithm that generated the analysis population of 900,000 to simulate the results of 10,000 microplate assays, assuming discrete HPV prevalences of 12%, 13%, 14%, 15%, and 16%. Using binomial draws, the algorithm created a vector of results for each prevalence and reassembled them into 96-well matrices for results distribution analysis of the number of positive cells and number and size of cell clusters (≥2 positive cells horizontally or vertically adjacent) per matrix. For simulation conditions of 12% and 16% HPV prevalence, 95% of the matrices displayed the following characteristics: 5 to 17 and 8 to 22 total positive cells, 0 to 4 and 0 to 5 positive cell clusters, and largest cluster sizes of up to 5 and up to 6 positive cells, respectively. Our results suggest that screening programs in regions with an oncogenic HPV prevalence of 12% to 16% can expect 5 to 22 positive results per microplate in approximately 95% of assays and 0 to 5 positive results clusters with no cluster larger than 6 positive results. Results consistently outside of these ranges deviate from what is statistically expected and could be the result of well-to-well contamination. Our results provide guidance that laboratories can use to identify microplates suspicious for well-to-well contamination, enabling improved quality assurance.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

  20. Testing the statistical isotropy of large scale structure with multipole vectors

    International Nuclear Information System (INIS)

    Zunckel, Caroline; Huterer, Dragan; Starkman, Glenn D.

    2011-01-01

    A fundamental assumption in cosmology is that of statistical isotropy - that the Universe, on average, looks the same in every direction in the sky. Statistical isotropy has recently been tested stringently using cosmic microwave background data, leading to intriguing results on large angular scales. Here we apply some of the same techniques used in the cosmic microwave background to the distribution of galaxies on the sky. Using the multipole vector approach, where each multipole in the harmonic decomposition of galaxy density field is described by unit vectors and an amplitude, we lay out the basic formalism of how to reconstruct the multipole vectors and their statistics out of galaxy survey catalogs. We apply the algorithm to synthetic galaxy maps, and study the sensitivity of the multipole vector reconstruction accuracy to the density, depth, sky coverage, and pixelization of galaxy catalog maps.

  1. Statistical universalities in fragmentation under scaling symmetry with a constant frequency of fragmentation

    International Nuclear Information System (INIS)

    Gorokhovski, M A; Saveliev, V L

    2008-01-01

    This paper analyses statistical universalities that arise over time during constant frequency fragmentation under scaling symmetry. The explicit expression of particle-size distribution obtained from the evolution kinetic equation shows that, with increasing time, the initial distribution tends to the ultimate steady-state delta function through at least two intermediate universal asymptotics. The earlier asymptotic is the well-known log-normal distribution of Kolmogorov (1941 Dokl. Akad. Nauk. SSSR 31 99-101). This distribution is the first universality and has two parameters: the first and the second logarithmic moments of the fragmentation intensity spectrum. The later asymptotic is a power function (stronger universality) with a single parameter that is given by the ratio of the first two logarithmic moments. At large times, the first universality implies that the evolution equation can be reduced exactly to the Fokker-Planck equation instead of making the widely used but inconsistent assumption about the smallness of higher than second order moments. At even larger times, the second universality shows evolution towards a fractal state with dimension identified as a measure of the fracture resistance of the medium

  2. Vital Statistics of Panstrongylus geniculatus (Latreille 1811 (Hemiptera: Reduviidae under Experimental Conditions

    Directory of Open Access Journals (Sweden)

    Cabello Daniel R

    1998-01-01

    Full Text Available A statistical evaluation of the population dynamics of Panstrongylus geniculatus is based on a cohort experiment conducted under controlled laboratory conditions. Animals were fed on hen every 15 days. Egg incubation took 21 days; mean duration of 1st, 2nd, 3rd, 4th, and 5th instar nymphs was 25, 30, 58, 62, and 67 days, respectively; mean nymphal development time was 39 weeks and adult longevity was 72 weeks. Females reproduced during 30 weeks, producing an average of 61.6 eggs for female on its lifetime; the average number of eggs/female/week was 2.1. Total number of eggs produced by the cohort was 1379. Average hatch for the cohort was 88.9%; it was not affected by age of the mother. Age specific survival and reproduction tables were constructed. The following population parameters were evaluated, generation time was 36.1 weeks; net reproduction rate was 89.4; intrinsic rate of natural increase was 0.125; instantaneous birth and death rates were 0.163 and 0.039 respectively; finite rate of increase was 1.13; total reproductive value was 1196 and stable age distribution was 31.2% eggs, 64.7% nymphs and 4.1% adults. Finally the population characteristics of P. geniculatus lead to the conclusion that this species is a K strategist.

  3. Studies in the statistical and thermal properties of hadronic matter under some extreme conditions

    International Nuclear Information System (INIS)

    Chase, K.C.; Mekjian, A.Z.; Bhattacharyya, P.

    1997-01-01

    The thermal and statistical properties of hadronic matter under some extreme conditions are investigated using an exactly solvable canonical ensemble model. A unified model describing both the fragmentation of nuclei and the thermal properties of hadronic matter is developed. Simple expressions are obtained for quantities such as the hadronic equation of state, specific heat, compressibility, entropy, and excitation energy as a function of temperature and density. These expressions encompass the fermionic aspect of nucleons, such as degeneracy pressure and Fermi energy at low temperatures and the ideal gas laws at high temperatures and low density. Expressions are developed which connect these two extremes with behavior that resembles an ideal Bose gas with its associated Bose condensation. In the thermodynamic limit, an infinite cluster exists below a certain critical condition in a manner similar to the sudden appearance of the infinite cluster in percolation theory. The importance of multiplicity fluctuations is discussed and some recent data from the EOS collaboration on critical point behavior of nuclei can be accounted for using simple expressions obtained from the model. copyright 1997 The American Physical Society

  4. Nonequilibrium statistical theory of bubble nucleation and growth under neutron and proton irradiation

    International Nuclear Information System (INIS)

    Yu, J.; Sommer, W.F.; Bradbury, J.N.

    1986-01-01

    Microstructural evolution in metals under particle irradiation is described by a non-equilibrium statistics method. This method gives a set of equations for the evolution of bubbles and an approximate solution for a distribution function of bubble size as a function of fluence and temperature. The distribution function gives the number of bubbles of radius r at time t, N(r,t)dr, as a function of size, r/r 0 (r 0 is the radius of a bubble nucleus). It is found that N(r,t)dr increases with fluence. Also, the peak value of N(r,t)dt shifts to higher r/r 0 with increasing fluence. Nucleation depends mainly on helium concentration and defect cluster concentration while bubble growth is controlled mainly by the vacancy concentration and a fluctuation coefficient. If suitable material parameters are chosen, a reasonable distribution function for bubble size is obtained. The helium diffusion coefficient is found to be less than that for vacancies by five orders of magnitude. The fraction of helium remaining in matrix is less than 10 -2 ; the majority of the helium is associated with the bubbles

  5. Statistical optimization for tannase production from Aspergillus niger under submerged fermentation.

    Science.gov (United States)

    Sharma, S; Agarwal, L; Saxena, R K

    2007-06-01

    Statistically based experimental design was employed for the optimization of fermentation conditions for maximum production of enzyme tannase from Aspergillus niger. Central composite rotatable design (CCRD) falling under response surface methodology (RSM) was used. Based on the results of 'one-at-a-time' approach in submerged fermentation, the most influencing factors for tannase production from A. niger were concentrations of tannic acid and sodium nitrate, agitation rate and incubation period. Hence, to achieve the maximum yield of tannase, interaction of these factors was studied at optimum production pH of 5.0 by RSM. The optimum values of parameters obtained through RSM were 5% tannic acid, 0.8% sodium nitrate, 5.0 pH, 5 × 10(7) spores/50mL inoculum density, 150 rpm agitation and incubation period of 48 h which resulted in production of 19.7 UmL(-1) of the enzyme. This activity was almost double as compared to the amount obtained by 'one-at-a-time' approach (9.8 UmL(-1)).

  6. Observations in the statistical analysis of NBG-18 nuclear graphite strength tests

    International Nuclear Information System (INIS)

    Hindley, Michael P.; Mitchell, Mark N.; Blaine, Deborah C.; Groenwold, Albert A.

    2012-01-01

    Highlights: ► Statistical analysis of NBG-18 nuclear graphite strength test. ► A Weibull distribution and normal distribution is tested for all data. ► A Bimodal distribution in the CS data is confirmed. ► The CS data set has the lowest variance. ► A Combined data set is formed and has Weibull distribution. - Abstract: The purpose of this paper is to report on the selection of a statistical distribution chosen to represent the experimental material strength of NBG-18 nuclear graphite. Three large sets of samples were tested during the material characterisation of the Pebble Bed Modular Reactor and Core Structure Ceramics materials. These sets of samples are tensile strength, flexural strength and compressive strength (CS) measurements. A relevant statistical fit is determined and the goodness of fit is also evaluated for each data set. The data sets are also normalised for ease of comparison, and combined into one representative data set. The validity of this approach is demonstrated. A second failure mode distribution is found on the CS test data. Identifying this failure mode supports the similar observations made in the past. The success of fitting the Weibull distribution through the normalised data sets allows us to improve the basis for the estimates of the variability. This could also imply that the variability on the graphite strength for the different strength measures is based on the same flaw distribution and thus a property of the material.

  7. Test of statistical models of the ν-delayed neutron emission by application of the Monte Carlo method

    International Nuclear Information System (INIS)

    Ohm, H.

    1982-01-01

    Using the example of the delayed neutron spectrum of 24 s- 137 I the statistical model is tested in view of its applicability. A computer code was developed which simulates delayed neutron spectra by the Monte Carlo method under the assumption that the transition probabilities of the ν and the neutron decays obey the Porter-Thomas distribution while the distances of the neutron emitting levels are Wigner distribution. Gramow-Teller ν-transitions and simply forbidden ν-transitions from the preceding nucleus to the emitting nucleus were regarded. (orig./HSI) [de

  8. Combining Multiple Hypothesis Testing with Machine Learning Increases the Statistical Power of Genome-wide Association Studies

    Science.gov (United States)

    Mieth, Bettina; Kloft, Marius; Rodríguez, Juan Antonio; Sonnenburg, Sören; Vobruba, Robin; Morcillo-Suárez, Carlos; Farré, Xavier; Marigorta, Urko M.; Fehr, Ernst; Dickhaus, Thorsten; Blanchard, Gilles; Schunk, Daniel; Navarro, Arcadi; Müller, Klaus-Robert

    2016-01-01

    The standard approach to the analysis of genome-wide association studies (GWAS) is based on testing each position in the genome individually for statistical significance of its association with the phenotype under investigation. To improve the analysis of GWAS, we propose a combination of machine learning and statistical testing that takes correlation structures within the set of SNPs under investigation in a mathematically well-controlled manner into account. The novel two-step algorithm, COMBI, first trains a support vector machine to determine a subset of candidate SNPs and then performs hypothesis tests for these SNPs together with an adequate threshold correction. Applying COMBI to data from a WTCCC study (2007) and measuring performance as replication by independent GWAS published within the 2008–2015 period, we show that our method outperforms ordinary raw p-value thresholding as well as other state-of-the-art methods. COMBI presents higher power and precision than the examined alternatives while yielding fewer false (i.e. non-replicated) and more true (i.e. replicated) discoveries when its results are validated on later GWAS studies. More than 80% of the discoveries made by COMBI upon WTCCC data have been validated by independent studies. Implementations of the COMBI method are available as a part of the GWASpi toolbox 2.0. PMID:27892471

  9. Computer processing of 14C data; statistical tests and corrections of data

    International Nuclear Information System (INIS)

    Obelic, B.; Planinic, J.

    1977-01-01

    The described computer program calculates the age of samples and performs statistical tests and corrections of data. Data are obtained from the proportional counter that measures anticoincident pulses per 20 minute intervals. After every 9th interval the counter measures total number of counts per interval. Input data are punched on cards. The output list contains input data schedule and the following results: mean CPM value, correction of CPM for normal pressure and temperature (NTP), sample age calculation based on 14 C half life of 5570 and 5730 years, age correction for NTP, dendrochronological corrections and the relative radiocarbon concentration. All results are given with one standard deviation. Input data test (Chauvenet's criterion), gas purity test, standard deviation test and test of the data processor are also included in the program. (author)

  10. Assessing Regional Scale Variability in Extreme Value Statistics Under Altered Climate Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Brunsell, Nathaniel [Univ. of Kansas, Lawrence, KS (United States); Mechem, David [Univ. of Kansas, Lawrence, KS (United States); Ma, Chunsheng [Wichita State Univ., KS (United States)

    2015-02-20

    Recent studies have suggested that low-frequency modes of climate variability can significantly influence regional climate. The climatology associated with extreme events has been shown to be particularly sensitive. This has profound implications for droughts, heat waves, and food production. We propose to examine regional climate simulations conducted over the continental United States by applying a recently developed technique which combines wavelet multi–resolution analysis with information theory metrics. This research is motivated by two fundamental questions concerning the spatial and temporal structure of extreme events. These questions are 1) what temporal scales of the extreme value distributions are most sensitive to alteration by low-frequency climate forcings and 2) what is the nature of the spatial structure of variation in these timescales? The primary objective is to assess to what extent information theory metrics can be useful in characterizing the nature of extreme weather phenomena. Specifically, we hypothesize that (1) changes in the nature of extreme events will impact the temporal probability density functions and that information theory metrics will be sensitive these changes and (2) via a wavelet multi–resolution analysis, we will be able to characterize the relative contribution of different timescales on the stochastic nature of extreme events. In order to address these hypotheses, we propose a unique combination of an established regional climate modeling approach and advanced statistical techniques to assess the effects of low-frequency modes on climate extremes over North America. The behavior of climate extremes in RCM simulations for the 20th century will be compared with statistics calculated from the United States Historical Climatology Network (USHCN) and simulations from the North American Regional Climate Change Assessment Program (NARCCAP). This effort will serve to establish the baseline behavior of climate extremes, the

  11. Using a Statistical Approach to Anticipate Leaf Wetness Duration Under Climate Change in France

    Science.gov (United States)

    Huard, F.; Imig, A. F.; Perrin, P.

    2014-12-01

    Leaf wetness plays a major role in the development of fungal plant diseases. Leaf wetness duration (LWD) above a threshold value is determinant for infection and can be seen as a good indicator of impact of climate on infection occurrence and risk. As LWD is not widely measured, several methods, based on physics and empirical approach, have been developed to estimate it from weather data. Many LWD statistical models do exist, but the lack of standard for measurements require reassessments. A new empirical LWD model, called MEDHI (Modèle d'Estimation de la Durée d'Humectation à l'Inra) was developed for french configuration for wetness sensors (angle : 90°, height : 50 cm). This deployment is different from what is usually recommended from constructors or authors in other countries (angle from 10 to 60°, height from 10 to 150 cm…). MEDHI is a decision support system based on hourly climatic conditions at time steps n and n-1 taking account relative humidity, rainfall and previously simulated LWD. Air temperature, relative humidity, wind speed, rain and LWD data from several sensors with 2 configurations were measured during 6 months in Toulouse and Avignon (South West and South East of France) to calibrate MEDHI. A comparison of empirical models : NHRH (RH threshold), DPD (dew point depression), CART (classification and regression tree analysis dependant on RH, wind speed and dew point depression) and MEDHI, using meteorological and LWD measurements obtained during 5 months in Toulouse, showed that the development of this new model MEHDI was definitely better adapted to French conditions. In the context of climate change, MEDHI was used for mapping the evolution of leaf wetness duration in France from 1950 to 2100 with the French regional climate model ALADIN under different Representative Concentration Pathways (RCPs) and using a QM (Quantile-Mapping) statistical downscaling method. Results give information on the spatial distribution of infection risks

  12. A review of statistical methods for testing genetic anticipation: looking for an answer in Lynch syndrome

    DEFF Research Database (Denmark)

    Boonstra, Philip S; Gruber, Stephen B; Raymond, Victoria M

    2010-01-01

    Anticipation, manifested through decreasing age of onset or increased severity in successive generations, has been noted in several genetic diseases. Statistical methods for genetic anticipation range from a simple use of the paired t-test for age of onset restricted to affected parent-child pairs......, and this right truncation effect is more pronounced in children than in parents. In this study, we first review different statistical methods for testing genetic anticipation in affected parent-child pairs that address the issue of bias due to right truncation. Using affected parent-child pair data, we compare...... the issue of multiplex ascertainment and its effect on the different methods. We then focus on exploring genetic anticipation in Lynch syndrome and analyze new data on the age of onset in affected parent-child pairs from families seen at the University of Michigan Cancer Genetics clinic with a mutation...

  13. Statistical hypothesis testing and common misinterpretations: Should we abandon p-value in forensic science applications?

    Science.gov (United States)

    Taroni, F; Biedermann, A; Bozza, S

    2016-02-01

    Many people regard the concept of hypothesis testing as fundamental to inferential statistics. Various schools of thought, in particular frequentist and Bayesian, have promoted radically different solutions for taking a decision about the plausibility of competing hypotheses. Comprehensive philosophical comparisons about their advantages and drawbacks are widely available and continue to span over large debates in the literature. More recently, controversial discussion was initiated by an editorial decision of a scientific journal [1] to refuse any paper submitted for publication containing null hypothesis testing procedures. Since the large majority of papers published in forensic journals propose the evaluation of statistical evidence based on the so called p-values, it is of interest to expose the discussion of this journal's decision within the forensic science community. This paper aims to provide forensic science researchers with a primer on the main concepts and their implications for making informed methodological choices. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  14. Testing a statistical method of global mean palotemperature estimations in a long climate simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zorita, E.; Gonzalez-Rouco, F. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Hydrophysik

    2001-07-01

    Current statistical methods of reconstructing the climate of the last centuries are based on statistical models linking climate observations (temperature, sea-level-pressure) and proxy-climate data (tree-ring chronologies, ice-cores isotope concentrations, varved sediments, etc.). These models are calibrated in the instrumental period, and the longer time series of proxy data are then used to estimate the past evolution of the climate variables. Using such methods the global mean temperature of the last 600 years has been recently estimated. In this work this method of reconstruction is tested using data from a very long simulation with a climate model. This testing allows to estimate the errors of the estimations as a function of the number of proxy data and the time scale at which the estimations are probably reliable. (orig.)

  15. A statistical method for testing epidemiological results, as applied to the Hanford worker population

    International Nuclear Information System (INIS)

    Brodsky, A.

    1979-01-01

    Some recent reports of Mancuso, Stewart and Kneale claim findings of radiation-produced cancer in the Hanford worker population. These claims are based on statistical computations that use small differences in accumulated exposures between groups dying of cancer and groups dying of other causes; actual mortality and longevity were not reported. This paper presents a statistical method for evaluation of actual mortality and longevity longitudinally over time, as applied in a primary analysis of the mortality experience of the Hanford worker population. Although available, this method was not utilized in the Mancuso-Stewart-Kneale paper. The author's preliminary longitudinal analysis shows that the gross mortality experience of persons employed at Hanford during 1943-70 interval did not differ significantly from that of certain controls, when both employees and controls were selected from families with two or more offspring and comparison were matched by age, sex, race and year of entry into employment. This result is consistent with findings reported by Sanders (Health Phys. vol.35, 521-538, 1978). The method utilizes an approximate chi-square (1 D.F.) statistic for testing population subgroup comparisons, as well as the cumulation of chi-squares (1 D.F.) for testing the overall result of a particular type of comparison. The method is available for computer testing of the Hanford mortality data, and could also be adapted to morbidity or other population studies. (author)

  16. Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses.

    Science.gov (United States)

    Faul, Franz; Erdfelder, Edgar; Buchner, Axel; Lang, Albert-Georg

    2009-11-01

    G*Power is a free power analysis program for a variety of statistical tests. We present extensions and improvements of the version introduced by Faul, Erdfelder, Lang, and Buchner (2007) in the domain of correlation and regression analyses. In the new version, we have added procedures to analyze the power of tests based on (1) single-sample tetrachoric correlations, (2) comparisons of dependent correlations, (3) bivariate linear regression, (4) multiple linear regression based on the random predictor model, (5) logistic regression, and (6) Poisson regression. We describe these new features and provide a brief introduction to their scope and handling.

  17. Acoustic emission monitoring of the bending under tension test

    DEFF Research Database (Denmark)

    Moghadam, Marcel; Sulaiman, Mohd Hafis Bin; Christiansen, Peter

    2017-01-01

    Preliminary investigations have shown that acoustic emission has promising aspects as an online monitoring technique for assessment of tribological conditions during metal forming as regards to determination of the onset of galling. In the present study the acoustic emission measuring technique h...... in BUT testing has been found to describe the frictional conditions during forming well and to allow for accurate assessment of the limits of lubrication....... been applied for online monitoring of the frictional conditions experienced during Bending Under Tension (BUT) testing. The BUT test emulates the forming conditions experienced when drawing sheet material over a die curvature as in deep drawing processes. Monitoring of the developed acoustic emission...

  18. Statistical inference on censored data for targeted clinical trials under enrichment design.

    Science.gov (United States)

    Chen, Chen-Fang; Lin, Jr-Rung; Liu, Jen-Pei

    2013-01-01

    For the traditional clinical trials, inclusion and exclusion criteria are usually based on some clinical endpoints; the genetic or genomic variability of the trial participants are not totally utilized in the criteria. After completion of the human genome project, the disease targets at the molecular level can be identified and can be utilized for the treatment of diseases. However, the accuracy of diagnostic devices for identification of such molecular targets is usually not perfect. Some of the patients enrolled in targeted clinical trials with a positive result for the molecular target might not have the specific molecular targets. As a result, the treatment effect may be underestimated in the patient population truly with the molecular target. To resolve this issue, under the exponential distribution, we develop inferential procedures for the treatment effects of the targeted drug based on the censored endpoints in the patients truly with the molecular targets. Under an enrichment design, we propose using the expectation-maximization algorithm in conjunction with the bootstrap technique to incorporate the inaccuracy of the diagnostic device for detection of the molecular targets on the inference of the treatment effects. A simulation study was conducted to empirically investigate the performance of the proposed methods. Simulation results demonstrate that under the exponential distribution, the proposed estimator is nearly unbiased with adequate precision, and the confidence interval can provide adequate coverage probability. In addition, the proposed testing procedure can adequately control the size with sufficient power. On the other hand, when the proportional hazard assumption is violated, additional simulation studies show that the type I error rate is not controlled at the nominal level and is an increasing function of the positive predictive value. A numerical example illustrates the proposed procedures. Copyright © 2013 John Wiley & Sons, Ltd.

  19. Polystyrene cryostat facilitates testing tensile specimens under liquid nitrogen

    Science.gov (United States)

    Shogan, R. P.; Skalka, R. J.

    1967-01-01

    Lightweight cryostat made of expanded polystyrene reduces eccentricity in a tensile system being tested under liquid nitrogen. The cryostat is attached directly to the tensile system by a special seal, reducing misalignment effects due to cryostat weight, and facilitates viewing and loading of the specimens.

  20. Testing statistical significance scores of sequence comparison methods with structure similarity

    Directory of Open Access Journals (Sweden)

    Leunissen Jack AM

    2006-10-01

    Full Text Available Abstract Background In the past years the Smith-Waterman sequence comparison algorithm has gained popularity due to improved implementations and rapidly increasing computing power. However, the quality and sensitivity of a database search is not only determined by the algorithm but also by the statistical significance testing for an alignment. The e-value is the most commonly used statistical validation method for sequence database searching. The CluSTr database and the Protein World database have been created using an alternative statistical significance test: a Z-score based on Monte-Carlo statistics. Several papers have described the superiority of the Z-score as compared to the e-value, using simulated data. We were interested if this could be validated when applied to existing, evolutionary related protein sequences. Results All experiments are performed on the ASTRAL SCOP database. The Smith-Waterman sequence comparison algorithm with both e-value and Z-score statistics is evaluated, using ROC, CVE and AP measures. The BLAST and FASTA algorithms are used as reference. We find that two out of three Smith-Waterman implementations with e-value are better at predicting structural similarities between proteins than the Smith-Waterman implementation with Z-score. SSEARCH especially has very high scores. Conclusion The compute intensive Z-score does not have a clear advantage over the e-value. The Smith-Waterman implementations give generally better results than their heuristic counterparts. We recommend using the SSEARCH algorithm combined with e-values for pairwise sequence comparisons.

  1. Comparing Student Success and Understanding in Introductory Statistics under Consensus and Simulation-Based Curricula

    Science.gov (United States)

    Hldreth, Laura A.; Robison-Cox, Jim; Schmidt, Jade

    2018-01-01

    This study examines the transferability of results from previous studies of simulation-based curriculum in introductory statistics using data from 3,500 students enrolled in an introductory statistics course at Montana State University from fall 2013 through spring 2016. During this time, four different curricula, a traditional curriculum and…

  2. Analysis of North Korea's Nuclear Tests under Prospect Theory

    International Nuclear Information System (INIS)

    Lee, Han Myung; Ryu, Jae Soo; Lee, Kwang Seok; Lee, Dong Hoon; Jun, Eunju; Kim, Mi Jin

    2013-01-01

    North Korea has chosen nuclear weapons as the means to protect its sovereignty. Despite international society's endeavors and sanctions to encourage North Korea to abandon its nuclear ambition, North Korea has repeatedly conducted nuclear testing. In this paper, the reason for North Korea's addiction to a nuclear arsenal is addressed within the framework of cognitive psychology. The prospect theory addresses an epistemological approach usually overlooked in rational choice theories. It provides useful implications why North Korea, being under a crisis situation has thrown out a stable choice but taken on a risky one such as nuclear testing. Under the viewpoint of prospect theory, nuclear tests by North Korea can be understood as follows: The first nuclear test in 2006 is seen as a trial to escape from loss areas such as financial sanctions and regime threats; the second test in 2009 was interpreted as a consequence of the strategy to recover losses by making a direct confrontation against the United States; and the third test in 2013 was understood as an attempt to strengthen internal solidarity after Kim Jong-eun inherited the dynasty, as well as to enhance bargaining power against the United States. Thus, it can be summarized that Pyongyang repeated its nuclear tests to escape from a negative domain and to settle into a positive one. In addition, in the future, North Korea may not be willing to readily give up its nuclear capabilities to ensure the survival of its own regime

  3. A powerful score-based test statistic for detecting gene-gene co-association.

    Science.gov (United States)

    Xu, Jing; Yuan, Zhongshang; Ji, Jiadong; Zhang, Xiaoshuai; Li, Hongkai; Wu, Xuesen; Xue, Fuzhong; Liu, Yanxun

    2016-01-29

    The genetic variants identified by Genome-wide association study (GWAS) can only account for a small proportion of the total heritability for complex disease. The existence of gene-gene joint effects which contains the main effects and their co-association is one of the possible explanations for the "missing heritability" problems. Gene-gene co-association refers to the extent to which the joint effects of two genes differ from the main effects, not only due to the traditional interaction under nearly independent condition but the correlation between genes. Generally, genes tend to work collaboratively within specific pathway or network contributing to the disease and the specific disease-associated locus will often be highly correlated (e.g. single nucleotide polymorphisms (SNPs) in linkage disequilibrium). Therefore, we proposed a novel score-based statistic (SBS) as a gene-based method for detecting gene-gene co-association. Various simulations illustrate that, under different sample sizes, marginal effects of causal SNPs and co-association levels, the proposed SBS has the better performance than other existed methods including single SNP-based and principle component analysis (PCA)-based logistic regression model, the statistics based on canonical correlations (CCU), kernel canonical correlation analysis (KCCU), partial least squares path modeling (PLSPM) and delta-square (δ (2)) statistic. The real data analysis of rheumatoid arthritis (RA) further confirmed its advantages in practice. SBS is a powerful and efficient gene-based method for detecting gene-gene co-association.

  4. Filter Media Tests Under Simulated Martian Atmospheric Conditions

    Science.gov (United States)

    Agui, Juan H.

    2016-01-01

    Human exploration of Mars will require the optimal utilization of planetary resources. One of its abundant resources is the Martian atmosphere that can be harvested through filtration and chemical processes that purify and separate it into its gaseous and elemental constituents. Effective filtration needs to be part of the suite of resource utilization technologies. A unique testing platform is being used which provides the relevant operational and instrumental capabilities to test articles under the proper simulated Martian conditions. A series of tests were conducted to assess the performance of filter media. Light sheet imaging of the particle flow provided a means of detecting and quantifying particle concentrations to determine capturing efficiencies. The media's efficiency was also evaluated by gravimetric means through a by-layer filter media configuration. These tests will help to establish techniques and methods for measuring capturing efficiency and arrestance of conventional fibrous filter media. This paper will describe initial test results on different filter media.

  5. Confidence intervals permit, but don't guarantee, better inference than statistical significance testing

    Directory of Open Access Journals (Sweden)

    Melissa Coulson

    2010-07-01

    Full Text Available A statistically significant result, and a non-significant result may differ little, although significance status may tempt an interpretation of difference. Two studies are reported that compared interpretation of such results presented using null hypothesis significance testing (NHST, or confidence intervals (CIs. Authors of articles published in psychology, behavioural neuroscience, and medical journals were asked, via email, to interpret two fictitious studies that found similar results, one statistically significant, and the other non-significant. Responses from 330 authors varied greatly, but interpretation was generally poor, whether results were presented as CIs or using NHST. However, when interpreting CIs respondents who mentioned NHST were 60% likely to conclude, unjustifiably, the two results conflicted, whereas those who interpreted CIs without reference to NHST were 95% likely to conclude, justifiably, the two results were consistent. Findings were generally similar for all three disciplines. An email survey of academic psychologists confirmed that CIs elicit better interpretations if NHST is not invoked. Improved statistical inference can result from encouragement of meta-analytic thinking and use of CIs but, for full benefit, such highly desirable statistical reform requires also that researchers interpret CIs without recourse to NHST.

  6. Drop Test Results of CRDM under Seismic Loads

    International Nuclear Information System (INIS)

    Choi, Myoung-Hwan; Cho, Yeong-Garp; Kim, Gyeong-Ho; Sun, Jong-Oh; Huh, Hyung

    2016-01-01

    This paper describes the test results to demonstrate the drop performance of CRDM under seismic loads. The top-mounted CRDM driven by the stepping motor for Jordan Research and Training Reactor (JRTR) has been developed in KAERI. The CRDM for JRTR has been optimized by the design improvement based on that of the HANARO. It is necessary to verify the drop performance under seismic loads such as operating basis earthquake (OBE) and safe shutdown earthquake (SSE). Especially, the CAR drop times are important data for the safety analysis. confirm the drop performance under seismic loads. The delay of drop time at Rig no. 2 due to seismic loads is greater than that at Rig no. 3. The total pure drop times under seismic loads are estimated as 1.169 and 1.855, respectively

  7. Drop Test Results of CRDM under Seismic Loads

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Myoung-Hwan; Cho, Yeong-Garp; Kim, Gyeong-Ho; Sun, Jong-Oh; Huh, Hyung [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    This paper describes the test results to demonstrate the drop performance of CRDM under seismic loads. The top-mounted CRDM driven by the stepping motor for Jordan Research and Training Reactor (JRTR) has been developed in KAERI. The CRDM for JRTR has been optimized by the design improvement based on that of the HANARO. It is necessary to verify the drop performance under seismic loads such as operating basis earthquake (OBE) and safe shutdown earthquake (SSE). Especially, the CAR drop times are important data for the safety analysis. confirm the drop performance under seismic loads. The delay of drop time at Rig no. 2 due to seismic loads is greater than that at Rig no. 3. The total pure drop times under seismic loads are estimated as 1.169 and 1.855, respectively.

  8. Filtering a statistically exactly solvable test model for turbulent tracers from partial observations

    International Nuclear Information System (INIS)

    Gershgorin, B.; Majda, A.J.

    2011-01-01

    A statistically exactly solvable model for passive tracers is introduced as a test model for the authors' Nonlinear Extended Kalman Filter (NEKF) as well as other filtering algorithms. The model involves a Gaussian velocity field and a passive tracer governed by the advection-diffusion equation with an imposed mean gradient. The model has direct relevance to engineering problems such as the spread of pollutants in the air or contaminants in the water as well as climate change problems concerning the transport of greenhouse gases such as carbon dioxide with strongly intermittent probability distributions consistent with the actual observations of the atmosphere. One of the attractive properties of the model is the existence of the exact statistical solution. In particular, this unique feature of the model provides an opportunity to design and test fast and efficient algorithms for real-time data assimilation based on rigorous mathematical theory for a turbulence model problem with many active spatiotemporal scales. Here, we extensively study the performance of the NEKF which uses the exact first and second order nonlinear statistics without any approximations due to linearization. The role of partial and sparse observations, the frequency of observations and the observation noise strength in recovering the true signal, its spectrum, and fat tail probability distribution are the central issues discussed here. The results of our study provide useful guidelines for filtering realistic turbulent systems with passive tracers through partial observations.

  9. Needs of in-situ materials testing under neutron irradiation

    International Nuclear Information System (INIS)

    Noda, K.; Hishinuma, A.; Kiuchi, K.

    1989-01-01

    Under neutron irradiation, the component atoms of materials are displaced as primary knock-on atoms, and the energy of the primary knock-on atoms is consumed by electron excitation and nuclear collision. Elementary irradiation defects accumulate to form damage structure including voids and bubbles. In situ test under neutron irradiation is necessary for investigating into the effect of irradiation on creep behavior, the electric properties of ceramics, transport phenomena and so on. The in situ test is also important to investigate into the phenomena related to the chemical reaction with environment during irradiation. Accelerator type high energy neutron sources are preferable to fission reactors. In this paper, the needs and the research items of in situ test under neutron irradiation using a D-Li stripping type high energy neutron source on metallic and ceramic materials are described. Creep behavior is one of the most important mechanical properties, and depends strongly on irradiation environment, also it is closely related to microstructure. Irradiation affects the electric conductibity of ceramics and also their creep behavior. In this way, in situ test is necessary. (K.I.)

  10. Association testing for next-generation sequencing data using score statistics

    DEFF Research Database (Denmark)

    Skotte, Line; Korneliussen, Thorfinn Sand; Albrechtsen, Anders

    2012-01-01

    computationally feasible due to the use of score statistics. As part of the joint likelihood, we model the distribution of the phenotypes using a generalized linear model framework, which works for both quantitative and discrete phenotypes. Thus, the method presented here is applicable to case-control studies...... of genotype calls into account have been proposed; most require numerical optimization which for large-scale data is not always computationally feasible. We show that using a score statistic for the joint likelihood of observed phenotypes and observed sequencing data provides an attractive approach...... to association testing for next-generation sequencing data. The joint model accounts for the genotype classification uncertainty via the posterior probabilities of the genotypes given the observed sequencing data, which gives the approach higher power than methods based on called genotypes. This strategy remains...

  11. Statistical auditing and randomness test of lotto k/N-type games

    Science.gov (United States)

    Coronel-Brizio, H. F.; Hernández-Montoya, A. R.; Rapallo, F.; Scalas, E.

    2008-11-01

    One of the most popular lottery games worldwide is the so-called “lotto k/N”. It considers N numbers 1,2,…,N from which k are drawn randomly, without replacement. A player selects k or more numbers and the first prize is shared amongst those players whose selected numbers match all of the k randomly drawn. Exact rules may vary in different countries. In this paper, mean values and covariances for the random variables representing the numbers drawn from this kind of game are presented, with the aim of using them to audit statistically the consistency of a given sample of historical results with theoretical values coming from a hypergeometric statistical model. The method can be adapted to test pseudorandom number generators.

  12. Statistics and methodology of multiple cell upset characterization under heavy ion irradiation

    International Nuclear Information System (INIS)

    Zebrev, G.I.; Gorbunov, M.S.; Useinov, R.G.; Emeliyanov, V.V.; Ozerov, A.I.; Anashin, V.S.; Kozyukov, A.E.; Zemtsov, K.S.

    2015-01-01

    Mean and partial cross-section concepts and their connections to multiplicity and statistics of multiple cell upsets (MCUs) in highly-scaled digital memories are introduced and discussed. The important role of the experimental determination of the upset statistics is emphasized. It was found that MCU may lead to quasi-linear dependence of cross-sections on linear energy transfer (LET). A new form of function for interpolation of mean cross-section dependences on LET has been proposed

  13. Global testing under sparse alternatives: ANOVA, multiple comparisons and the higher criticism

    OpenAIRE

    Arias-Castro, Ery; Candès, Emmanuel J.; Plan, Yaniv

    2011-01-01

    Testing for the significance of a subset of regression coefficients in a linear model, a staple of statistical analysis, goes back at least to the work of Fisher who introduced the analysis of variance (ANOVA). We study this problem under the assumption that the coefficient vector is sparse, a common situation in modern high-dimensional settings. Suppose we have $p$ covariates and that under the alternative, the response only depends upon the order of $p^{1-\\alpha}$ of those, $0\\le\\alpha\\le1$...

  14. A Note on Comparing the Power of Test Statistics at Low Significance Levels.

    Science.gov (United States)

    Morris, Nathan; Elston, Robert

    2011-01-01

    It is an obvious fact that the power of a test statistic is dependent upon the significance (alpha) level at which the test is performed. It is perhaps a less obvious fact that the relative performance of two statistics in terms of power is also a function of the alpha level. Through numerous personal discussions, we have noted that even some competent statisticians have the mistaken intuition that relative power comparisons at traditional levels such as α = 0.05 will be roughly similar to relative power comparisons at very low levels, such as the level α = 5 × 10 -8 , which is commonly used in genome-wide association studies. In this brief note, we demonstrate that this notion is in fact quite wrong, especially with respect to comparing tests with differing degrees of freedom. In fact, at very low alpha levels the cost of additional degrees of freedom is often comparatively low. Thus we recommend that statisticians exercise caution when interpreting the results of power comparison studies which use alpha levels that will not be used in practice.

  15. IEEE Std 101-1972: IEEE guide for the statistical analysis of thermal life test data

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Procedures for estimating the thermal life of electrical insulation systems and materials call for life tests at several temperatures, usually well above the expected normal operating temperature. By the selection of high temperatures for the tests, life of the insulation samples will be terminated, according to some selected failure criterion or criteria, within relatively short times -- typically one week to one year. The result of these thermally accelerated life tests will be a set of data of life values for a corresponding set of temperatures. Usually the data consist of a set of life values for each of two to four (occasionally more) test temperatures, 10 C to 25 C apart. The objective then is to establish from these data the mean life vales at each temperature and the functional dependence of life on temperature, as well as the statistical consistency and the confidence to be attributed to the mean life values and the functional life temperature dependence. The purpose of this guide is to assist in this objective and to give guidance for comparing the results of tests on different materials and of different tests on the same materials

  16. Using the method of statistic tests for determining the pressure in the UNC-600 vacuum chamber

    International Nuclear Information System (INIS)

    Kiver, A.M.; Mirzoev, K.G.

    1998-01-01

    The aim of the paper is to simulate the process of pumping-out the UNC-600 vacuum chamber. The simulation is carried out by the Monte-Carlo statistic test method. It is shown that the pressure value in every liner of the chamber may be determined from the pressure in the pump branch pipe, determined by the discharge current of this pump. Therefore, it is possible to precise the working pressure in the ion guide of the UNC-600 vacuum chamber [ru

  17. Statistical refinements for data analysis of mollusc reproduction tests: an example with Lymnaea stagnalis

    DEFF Research Database (Denmark)

    Holbech, Henrik

    -contribution of each individual to the measured response. Furthermore, the combination of a Gamma-Poisson stochastic part with a Weibull concentration-response model allowed accounting for the inter-replicate variability. Second, we checked for the possibility of optimizing the initial experimental design through...... was twofold. First, we refined the statistical analyses of reproduction data accounting for mortality all along the test period. The variable “number of clutches/eggs produced per individual-day” was used for EC x modelling, as classically done in epidemiology in order to account for the time...

  18. Selection of hidden layer nodes in neural networks by statistical tests

    International Nuclear Information System (INIS)

    Ciftcioglu, Ozer

    1992-05-01

    A statistical methodology for selection of the number of hidden layer nodes in feedforward neural networks is described. The method considers the network as an empirical model for the experimental data set subject to pattern classification so that the selection process becomes a model estimation through parameter identification. The solution is performed for an overdetermined estimation problem for identification using nonlinear least squares minimization technique. The number of the hidden layer nodes is determined as result of hypothesis testing. Accordingly the redundant network structure with respect to the number of parameters is avoided and the classification error being kept to a minimum. (author). 11 refs.; 4 figs.; 1 tab

  19. Profile of State Prisoners under Age 18, 1985-97. Bureau of Justice Statistics Special Report.

    Science.gov (United States)

    Strom, Kevin J.

    This report presents data on all individuals under age 18 in state prisons, whether under the original jurisdiction of the juvenile or adult criminal system. Most of the data are from the National Corrections Reporting Program. On December 31, 1997, less than 1% of inmates in state prisons were under age 18, a proportion that has remained stable…

  20. Person Fit Based on Statistical Process Control in an Adaptive Testing Environment. Research Report 98-13.

    Science.gov (United States)

    van Krimpen-Stoop, Edith M. L. A.; Meijer, Rob R.

    Person-fit research in the context of paper-and-pencil tests is reviewed, and some specific problems regarding person fit in the context of computerized adaptive testing (CAT) are discussed. Some new methods are proposed to investigate person fit in a CAT environment. These statistics are based on Statistical Process Control (SPC) theory. A…

  1. Kernel Machine SNP-set Testing under Multiple Candidate Kernels

    Science.gov (United States)

    Wu, Michael C.; Maity, Arnab; Lee, Seunggeun; Simmons, Elizabeth M.; Harmon, Quaker E.; Lin, Xinyi; Engel, Stephanie M.; Molldrem, Jeffrey J.; Armistead, Paul M.

    2013-01-01

    Joint testing for the cumulative effect of multiple single nucleotide polymorphisms grouped on the basis of prior biological knowledge has become a popular and powerful strategy for the analysis of large scale genetic association studies. The kernel machine (KM) testing framework is a useful approach that has been proposed for testing associations between multiple genetic variants and many different types of complex traits by comparing pairwise similarity in phenotype between subjects to pairwise similarity in genotype, with similarity in genotype defined via a kernel function. An advantage of the KM framework is its flexibility: choosing different kernel functions allows for different assumptions concerning the underlying model and can allow for improved power. In practice, it is difficult to know which kernel to use a priori since this depends on the unknown underlying trait architecture and selecting the kernel which gives the lowest p-value can lead to inflated type I error. Therefore, we propose practical strategies for KM testing when multiple candidate kernels are present based on constructing composite kernels and based on efficient perturbation procedures. We demonstrate through simulations and real data applications that the procedures protect the type I error rate and can lead to substantially improved power over poor choices of kernels and only modest differences in power versus using the best candidate kernel. PMID:23471868

  2. Testing of newly developed functional surfaces under pure sliding conditions

    DEFF Research Database (Denmark)

    Godi, Alessandro; Mohaghegh, Kamran; Grønbæk, J.

    2013-01-01

    the surfaces in an industrial context. In this paper, a number of experimental tests were performed using a novel test rig, called axial sliding test, simulating the contact of surfaces under pure sliding conditions. The aim of the experiments is to evaluate the frictional behavior of a new typology...... of textured surfaces, the so-called multifunctional surfaces, characterized by a plateau area able to bear loads and a deterministic pattern of lubricant pockets. Six surface typologies, namely three multifunctional and three machined using classical processes, were chosen to slide against a mirror....... The results comparison showed clearly how employing multifunctional surfaces can reduce friction forces up to 50 % at high normal loads compared to regularly ground or turned surfaces. Friction coefficients approximately equal to 0.12 were found for classically machined surfaces, whereas the values were 0...

  3. Experimental and statistical study on fracture boundary of non-irradiated Zircaloy-4 cladding tube under LOCA conditions

    Science.gov (United States)

    Narukawa, Takafumi; Yamaguchi, Akira; Jang, Sunghyon; Amaya, Masaki

    2018-02-01

    For estimating fracture probability of fuel cladding tube under loss-of-coolant accident conditions of light-water-reactors, laboratory-scale integral thermal shock tests were conducted on non-irradiated Zircaloy-4 cladding tube specimens. Then, the obtained binary data with respect to fracture or non-fracture of the cladding tube specimen were analyzed statistically. A method to obtain the fracture probability curve as a function of equivalent cladding reacted (ECR) was proposed using Bayesian inference for generalized linear models: probit, logit, and log-probit models. Then, model selection was performed in terms of physical characteristics and information criteria, a widely applicable information criterion and a widely applicable Bayesian information criterion. As a result, it was clarified that the log-probit model was the best among the three models to estimate the fracture probability in terms of the degree of prediction accuracy for both next data to be obtained and the true model. Using the log-probit model, it was shown that 20% ECR corresponded to a 5% probability level with a 95% confidence of fracture of the cladding tube specimens.

  4. Supporting Students to Develop Concepts Underlying Sampling and to Shuttle Between Contextual and Statistical Spheres

    NARCIS (Netherlands)

    Bakker, A.; Dierdorp, A.; Maanen, J.A. van; Eijkelhof, H.M.C.

    2012-01-01

    To stimulate students’ shuttling between contextual and statistical spheres, we based tasks on professional practices. This article focuses on two tasks to support reasoning about sampling by students aged 16-17. The purpose of the tasks was to find out which smaller sample size would have been

  5. Auditory Magnetoencephalographic Frequency-Tagged Responses Mirror the Ongoing Segmentation Processes Underlying Statistical Learning.

    Science.gov (United States)

    Farthouat, Juliane; Franco, Ana; Mary, Alison; Delpouve, Julie; Wens, Vincent; Op de Beeck, Marc; De Tiège, Xavier; Peigneux, Philippe

    2017-03-01

    Humans are highly sensitive to statistical regularities in their environment. This phenomenon, usually referred as statistical learning, is most often assessed using post-learning behavioural measures that are limited by a lack of sensibility and do not monitor the temporal dynamics of learning. In the present study, we used magnetoencephalographic frequency-tagged responses to investigate the neural sources and temporal development of the ongoing brain activity that supports the detection of regularities embedded in auditory streams. Participants passively listened to statistical streams in which tones were grouped as triplets, and to random streams in which tones were randomly presented. Results show that during exposure to statistical (vs. random) streams, tritone frequency-related responses reflecting the learning of regularities embedded in the stream increased in the left supplementary motor area and left posterior superior temporal sulcus (pSTS), whereas tone frequency-related responses decreased in the right angular gyrus and right pSTS. Tritone frequency-related responses rapidly developed to reach significance after 3 min of exposure. These results suggest that the incidental extraction of novel regularities is subtended by a gradual shift from rhythmic activity reflecting individual tone succession toward rhythmic activity synchronised with triplet presentation, and that these rhythmic processes are subtended by distinct neural sources.

  6. Statistical Analysis of the Polarimetric Cloud Analysis and Seeding Test (POLCAST) Field Projects

    Science.gov (United States)

    Ekness, Jamie Lynn

    The North Dakota farming industry brings in more than $4.1 billion annually in cash receipts. Unfortunately, agriculture sales vary significantly from year to year, which is due in large part to weather events such as hail storms and droughts. One method to mitigate drought is to use hygroscopic seeding to increase the precipitation efficiency of clouds. The North Dakota Atmospheric Research Board (NDARB) sponsored the Polarimetric Cloud Analysis and Seeding Test (POLCAST) research project to determine the effectiveness of hygroscopic seeding in North Dakota. The POLCAST field projects obtained airborne and radar observations, while conducting randomized cloud seeding. The Thunderstorm Identification Tracking and Nowcasting (TITAN) program is used to analyze radar data (33 usable cases) in determining differences in the duration of the storm, rain rate and total rain amount between seeded and non-seeded clouds. The single ratio of seeded to non-seeded cases is 1.56 (0.28 mm/0.18 mm) or 56% increase for the average hourly rainfall during the first 60 minutes after target selection. A seeding effect is indicated with the lifetime of the storms increasing by 41 % between seeded and non-seeded clouds for the first 60 minutes past seeding decision. A double ratio statistic, a comparison of radar derived rain amount of the last 40 minutes of a case (seed/non-seed), compared to the first 20 minutes (seed/non-seed), is used to account for the natural variability of the cloud system and gives a double ratio of 1.85. The Mann-Whitney test on the double ratio of seeded to non-seeded cases (33 cases) gives a significance (p-value) of 0.063. Bootstrapping analysis of the POLCAST set indicates that 50 cases would provide statistically significant results based on the Mann-Whitney test of the double ratio. All the statistical analysis conducted on the POLCAST data set show that hygroscopic seeding in North Dakota does increase precipitation. While an additional POLCAST field

  7. Statistical testing and power analysis for brain-wide association study.

    Science.gov (United States)

    Gong, Weikang; Wan, Lin; Lu, Wenlian; Ma, Liang; Cheng, Fan; Cheng, Wei; Grünewald, Stefan; Feng, Jianfeng

    2018-04-05

    The identification of connexel-wise associations, which involves examining functional connectivities between pairwise voxels across the whole brain, is both statistically and computationally challenging. Although such a connexel-wise methodology has recently been adopted by brain-wide association studies (BWAS) to identify connectivity changes in several mental disorders, such as schizophrenia, autism and depression, the multiple correction and power analysis methods designed specifically for connexel-wise analysis are still lacking. Therefore, we herein report the development of a rigorous statistical framework for connexel-wise significance testing based on the Gaussian random field theory. It includes controlling the family-wise error rate (FWER) of multiple hypothesis testings using topological inference methods, and calculating power and sample size for a connexel-wise study. Our theoretical framework can control the false-positive rate accurately, as validated empirically using two resting-state fMRI datasets. Compared with Bonferroni correction and false discovery rate (FDR), it can reduce false-positive rate and increase statistical power by appropriately utilizing the spatial information of fMRI data. Importantly, our method bypasses the need of non-parametric permutation to correct for multiple comparison, thus, it can efficiently tackle large datasets with high resolution fMRI images. The utility of our method is shown in a case-control study. Our approach can identify altered functional connectivities in a major depression disorder dataset, whereas existing methods fail. A software package is available at https://github.com/weikanggong/BWAS. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Resemblance profiles as clustering decision criteria: Estimating statistical power, error, and correspondence for a hypothesis test for multivariate structure.

    Science.gov (United States)

    Kilborn, Joshua P; Jones, David L; Peebles, Ernst B; Naar, David F

    2017-04-01

    Clustering data continues to be a highly active area of data analysis, and resemblance profiles are being incorporated into ecological methodologies as a hypothesis testing-based approach to clustering multivariate data. However, these new clustering techniques have not been rigorously tested to determine the performance variability based on the algorithm's assumptions or any underlying data structures. Here, we use simulation studies to estimate the statistical error rates for the hypothesis test for multivariate structure based on dissimilarity profiles (DISPROF). We concurrently tested a widely used algorithm that employs the unweighted pair group method with arithmetic mean (UPGMA) to estimate the proficiency of clustering with DISPROF as a decision criterion. We simulated unstructured multivariate data from different probability distributions with increasing numbers of objects and descriptors, and grouped data with increasing overlap, overdispersion for ecological data, and correlation among descriptors within groups. Using simulated data, we measured the resolution and correspondence of clustering solutions achieved by DISPROF with UPGMA against the reference grouping partitions used to simulate the structured test datasets. Our results highlight the dynamic interactions between dataset dimensionality, group overlap, and the properties of the descriptors within a group (i.e., overdispersion or correlation structure) that are relevant to resemblance profiles as a clustering criterion for multivariate data. These methods are particularly useful for multivariate ecological datasets that benefit from distance-based statistical analyses. We propose guidelines for using DISPROF as a clustering decision tool that will help future users avoid potential pitfalls during the application of methods and the interpretation of results.

  9. Field Test of Driven Pile Group under Lateral Loading

    Science.gov (United States)

    Gorska, Karolina; Rybak, Jaroslaw; Wyjadlowski, Marek

    2017-12-01

    All the geotechnical works need to be tested because the diversity of soil parameters is much higher than in other fields of construction. Horizontal load tests are necessary to determine the lateral capacity of driven piles subject to lateral load. Various load tests were carried out altogether on the test field in Kutno (Poland). While selecting the piles for load tests, different load combinations were taken into account. The piles with diverse length were chosen, on the basis of the previous tests of their length and integrity. The subsoil around the piles consisted of mineral soils: clays and medium compacted sands with the density index ID>0.50. The pile heads were free. The points of support of the “base” to which the dial gauges (displacement sensors) were fastened were located at the distance of 0.7 m from the side surface of the pile loaded laterally. In order to assure the independence of measurement, additional control (verifying) geodetic survey of the displacement of the piles subject to the load tests was carried out (by means of the alignment method). The trial load was imposed in stages by means of a hydraulic jack. The oil pressure in the actuator was corrected by means of a manual pump in order to ensure the constant value of the load in the on-going process of the displacement of the pile under test. On the basis of the obtained results it is possible to verify the numerical simulations of the behaviour of piles loaded by a lateral force.

  10. Confidence Intervals: From tests of statistical significance to confidence intervals, range hypotheses and substantial effects

    Directory of Open Access Journals (Sweden)

    Dominic Beaulieu-Prévost

    2006-03-01

    Full Text Available For the last 50 years of research in quantitative social sciences, the empirical evaluation of scientific hypotheses has been based on the rejection or not of the null hypothesis. However, more than 300 articles demonstrated that this method was problematic. In summary, null hypothesis testing (NHT is unfalsifiable, its results depend directly on sample size and the null hypothesis is both improbable and not plausible. Consequently, alternatives to NHT such as confidence intervals (CI and measures of effect size are starting to be used in scientific publications. The purpose of this article is, first, to provide the conceptual tools necessary to implement an approach based on confidence intervals, and second, to briefly demonstrate why such an approach is an interesting alternative to an approach based on NHT. As demonstrated in the article, the proposed CI approach avoids most problems related to a NHT approach and can often improve the scientific and contextual relevance of the statistical interpretations by testing range hypotheses instead of a point hypothesis and by defining the minimal value of a substantial effect. The main advantage of such a CI approach is that it replaces the notion of statistical power by an easily interpretable three-value logic (probable presence of a substantial effect, probable absence of a substantial effect and probabilistic undetermination. The demonstration includes a complete example.

  11. Estimation of In Situ Stresses with Hydro-Fracturing Tests and a Statistical Method

    Science.gov (United States)

    Lee, Hikweon; Ong, See Hong

    2018-03-01

    At great depths, where borehole-based field stress measurements such as hydraulic fracturing are challenging due to difficult downhole conditions or prohibitive costs, in situ stresses can be indirectly estimated using wellbore failures such as borehole breakouts and/or drilling-induced tensile failures detected by an image log. As part of such efforts, a statistical method has been developed in which borehole breakouts detected on an image log are used for this purpose (Song et al. in Proceedings on the 7th international symposium on in situ rock stress, 2016; Song and Chang in J Geophys Res Solid Earth 122:4033-4052, 2017). The method employs a grid-searching algorithm in which the least and maximum horizontal principal stresses ( S h and S H) are varied, and the corresponding simulated depth-related breakout width distribution as a function of the breakout angle ( θ B = 90° - half of breakout width) is compared to that observed along the borehole to determine a set of S h and S H having the lowest misfit between them. An important advantage of the method is that S h and S H can be estimated simultaneously in vertical wells. To validate the statistical approach, the method is applied to a vertical hole where a set of field hydraulic fracturing tests have been carried out. The stress estimations using the proposed method were found to be in good agreement with the results interpreted from the hydraulic fracturing test measurements.

  12. Partial discharge testing: a progress report. Statistical evaluation of PD data

    International Nuclear Information System (INIS)

    Warren, V.; Allan, J.

    2005-01-01

    It has long been known that comparing the partial discharge results obtained from a single machine is a valuable tool enabling companies to observe the gradual deterioration of a machine stator winding and thus plan appropriate maintenance for the machine. In 1998, at the annual Iris Rotating Machines Conference (IRMC), a paper was presented that compared thousands of PD test results to establish the criteria for comparing results from different machines and the expected PD levels. At subsequent annual Iris conferences, using similar analytical procedures, papers were presented that supported the previous criteria and: in 1999, established sensor location as an additional criterion; in 2000, evaluated the effect of insulation type and age on PD activity; in 2001, evaluated the effect of manufacturer on PD activity; in 2002, evaluated the effect of operating pressure for hydrogen-cooled machines; in 2003, evaluated the effect of insulation type and setting Trac alarms; in 2004, re-evaluated the effect of manufacturer on PD activity. Before going further in database analysis procedures, it would be prudent to statistically evaluate the anecdotal evidence observed to date. The goal was to determine which variables of machine conditions greatly influenced the PD results and which didn't. Therefore, this year's paper looks at the impact of operating voltage, machine type and winding type on the test results for air-cooled machines. Because of resource constraints, only data collected through 2003 was used; however, as before, it is still standardized for frequency bandwidth and pruned to include only full-load-hot (FLH) results collected for one sensor on operating machines. All questionable data, or data from off-line testing or unusual machine conditions was excluded, leaving 6824 results. Calibration of on-line PD test results is impractical; therefore, only results obtained using the same method of data collection and noise separation techniques are compared. For

  13. Testing of high-level waste forms under repository conditions

    International Nuclear Information System (INIS)

    Mc Menamin, T.

    1989-01-01

    The workshop on testing of high-level waste forms under repository conditions was held on 17 to 21 October 1988 in Cadarache, France, and sponsored by the Commission of the European Communities (CEC), the Commissariat a l'energie atomique (CEA) and the Savannah River Laboratory (US DOE). Participants included representatives from Australia, Belgium, Denmark, France, Germany, Italy, Japan, the Netherlands, Sweden, Switzerland, The United Kingdom and the United States. The first part of the conference featured a workshop on in situ testing of simulated nuclear waste forms and proposed package components, with an emphasis on the materials interface interactions tests (MIIT). MIIT is a sevent-part programme that involves field testing of 15 glass and waste form systems supplied by seven countries, along with potential canister and overpack materials as well as geologic samples, in the salt geology at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico, USA. This effort is still in progress and these proceedings document studies and findings obtained thus far. The second part of the meeting emphasized multinational experimental studies and results derived from repository systems simulation tests (RSST), which were performed in granite, clay and salt environments

  14. A robust TDT-type association test under informative parental missingness.

    Science.gov (United States)

    Chen, J H; Cheng, K F

    2011-02-10

    Many family-based association tests rely on the random transmission of alleles from parents to offspring. Among them, the transmission/disequilibrium test (TDT) may be considered to be the most popular statistical test. The TDT statistic and its variations were proposed to evaluate nonrandom transmission of alleles from parents to the diseased children. However, in family studies, parental genotypes may be missing due to parental death, loss, divorce, or other reasons. Under some missingness conditions, nonrandom transmission of alleles may still occur even when the gene and disease are not associated. As a consequence, the usual TDT-type tests would produce excessive false positive conclusions in association studies. In this paper, we propose a novel TDT-type association test which is not only simple in computation but also robust to the joint effect of population stratification and informative parental missingness. Our test is model-free and allows for different mechanisms of parental missingness across subpopulations. We use a simulation study to compare the performance of the new test with TDT and point out the advantage of the new method. Copyright © 2010 John Wiley & Sons, Ltd.

  15. Accounting providing of statistical analysis of intangible assets renewal under marketing strategy

    Directory of Open Access Journals (Sweden)

    I.R. Polishchuk

    2016-12-01

    Full Text Available The article analyzes the content of the Regulations on accounting policies of the surveyed enterprises in terms of the operations concerning the amortization of intangible assets on the following criteria: assessment on admission, determination of useful life, the period of depreciation, residual value, depreciation method, reflection in the financial statements, a unit of account, revaluation, formation of fair value. The characteristic of factors affecting the accounting policies and determining the mechanism for evaluating the completeness and timeliness of intangible assets renewal is showed. The algorithm for selecting the method of intangible assets amortization is proposed. The knowledge base of statistical analysis of timeliness and completeness of intangible assets renewal in terms of the developed internal reporting is expanded. The statistical indicators to assess the effectiveness of the amortization policy for intangible assets are proposed. The marketing strategies depending on the condition and amount of intangible assets in relation to increasing marketing potential for continuity of economic activity are described.

  16. Debate on GMOs health risks after statistical findings in regulatory tests.

    Science.gov (United States)

    de Vendômois, Joël Spiroux; Cellier, Dominique; Vélot, Christian; Clair, Emilie; Mesnage, Robin; Séralini, Gilles-Eric

    2010-10-05

    We summarize the major points of international debate on health risk studies for the main commercialized edible GMOs. These GMOs are soy, maize and oilseed rape designed to contain new pesticide residues since they have been modified to be herbicide-tolerant (mostly to Roundup) or to produce mutated Bt toxins. The debated alimentary chronic risks may come from unpredictable insertional mutagenesis effects, metabolic effects, or from the new pesticide residues. The most detailed regulatory tests on the GMOs are three-month long feeding trials of laboratory rats, which are biochemically assessed. The tests are not compulsory, and are not independently conducted. The test data and the corresponding results are kept in secret by the companies. Our previous analyses of regulatory raw data at these levels, taking the representative examples of three GM maize NK 603, MON 810, and MON 863 led us to conclude that hepatorenal toxicities were possible, and that longer testing was necessary. Our study was criticized by the company developing the GMOs in question and the regulatory bodies, mainly on the divergent biological interpretations of statistically significant biochemical and physiological effects. We present the scientific reasons for the crucially different biological interpretations and also highlight the shortcomings in the experimental protocols designed by the company. The debate implies an enormous responsibility towards public health and is essential due to nonexistent traceability or epidemiological studies in the GMO-producing countries.

  17. Multirods burst tests under loss-of-coolant conditions

    International Nuclear Information System (INIS)

    Kawasaki, S.; Uetsuka, H.; Furuta, T.

    1983-01-01

    In order to know the upper limit of coolant flow area restriction in a fuel assembly under loss-of-coolant accidents in LWRs, burst tests of fuel bundles were performed. Each bundle consisted of 49 rods(7x7 rods), and bursts were conducted in flowing steam. In some cases, 4 rods were replaced by control rods with guide tubes in a bundle. After the burst, the ballooning behavior of each rod and the degree of coolant flow area restriction in the bundle were measured. Ballooning behavior of rods and degree of coolant flow channel restriction in bundles with control rods were not different from those without control rods. The upper limit of coolant flow channel restriction under loss-of-coolant conditions was estimated to be about 80%. (author)

  18. Statistical and Conceptual Model Testing Geomorphic Principles through Quantification in the Middle Rio Grande River, NM.

    Science.gov (United States)

    Posner, A. J.

    2017-12-01

    The Middle Rio Grande River (MRG) traverses New Mexico from Cochiti to Elephant Butte reservoirs. Since the 1100s, cultivating and inhabiting the valley of this alluvial river has required various river training works. The mid-20th century saw a concerted effort to tame the river through channelization, Jetty Jacks, and dam construction. A challenge for river managers is to better understand the interactions between a river training works, dam construction, and the geomorphic adjustments of a desert river driven by spring snowmelt and summer thunderstorms carrying water and large sediment inputs from upstream and ephemeral tributaries. Due to its importance to the region, a vast wealth of data exists for conditions along the MRG. The investigation presented herein builds upon previous efforts by combining hydraulic model results, digitized planforms, and stream gage records in various statistical and conceptual models in order to test our understanding of this complex system. Spatially continuous variables were clipped by a set of river cross section data that is collected at decadal intervals since the early 1960s, creating a spatially homogenous database upon which various statistical testing was implemented. Conceptual models relate forcing variables and response variables to estimate river planform changes. The developed database, represents a unique opportunity to quantify and test geomorphic conceptual models in the unique characteristics of the MRG. The results of this investigation provides a spatially distributed characterization of planform variable changes, permitting managers to predict planform at a much higher resolution than previously available, and a better understanding of the relationship between flow regime and planform changes such as changes to longitudinal slope, sinuosity, and width. Lastly, data analysis and model interpretation led to the development of a new conceptual model for the impact of ephemeral tributaries in alluvial rivers.

  19. Cosmological Non-Gaussian Signature Detection: Comparing Performance of Different Statistical Tests

    Directory of Open Access Journals (Sweden)

    O. Forni

    2005-09-01

    Full Text Available Currently, it appears that the best method for non-Gaussianity detection in the cosmic microwave background (CMB consists in calculating the kurtosis of the wavelet coefficients. We know that wavelet-kurtosis outperforms other methods such as the bispectrum, the genus, ridgelet-kurtosis, and curvelet-kurtosis on an empirical basis, but relatively few studies have compared other transform-based statistics, such as extreme values, or more recent tools such as higher criticism (HC, or proposed “best possible” choices for such statistics. In this paper, we consider two models for transform-domain coefficients: (a a power-law model, which seems suited to the wavelet coefficients of simulated cosmic strings, and (b a sparse mixture model, which seems suitable for the curvelet coefficients of filamentary structure. For model (a, if power-law behavior holds with finite 8th moment, excess kurtosis is an asymptotically optimal detector, but if the 8th moment is not finite, a test based on extreme values is asymptotically optimal. For model (b, if the transform coefficients are very sparse, a recent test, higher criticism, is an optimal detector, but if they are dense, kurtosis is an optimal detector. Empirical wavelet coefficients of simulated cosmic strings have power-law character, infinite 8th moment, while curvelet coefficients of the simulated cosmic strings are not very sparse. In all cases, excess kurtosis seems to be an effective test in moderate-resolution imagery.

  20. Testing multiple statistical hypotheses resulted in spurious associations: a study of astrological signs and health.

    Science.gov (United States)

    Austin, Peter C; Mamdani, Muhammad M; Juurlink, David N; Hux, Janet E

    2006-09-01

    To illustrate how multiple hypotheses testing can produce associations with no clinical plausibility. We conducted a study of all 10,674,945 residents of Ontario aged between 18 and 100 years in 2000. Residents were randomly assigned to equally sized derivation and validation cohorts and classified according to their astrological sign. Using the derivation cohort, we searched through 223 of the most common diagnoses for hospitalization until we identified two for which subjects born under one astrological sign had a significantly higher probability of hospitalization compared to subjects born under the remaining signs combined (P<0.05). We tested these 24 associations in the independent validation cohort. Residents born under Leo had a higher probability of gastrointestinal hemorrhage (P=0.0447), while Sagittarians had a higher probability of humerus fracture (P=0.0123) compared to all other signs combined. After adjusting the significance level to account for multiple comparisons, none of the identified associations remained significant in either the derivation or validation cohort. Our analyses illustrate how the testing of multiple, non-prespecified hypotheses increases the likelihood of detecting implausible associations. Our findings have important implications for the analysis and interpretation of clinical studies.

  1. Portfolio selection problem with liquidity constraints under non-extensive statistical mechanics

    International Nuclear Information System (INIS)

    Zhao, Pan; Xiao, Qingxian

    2016-01-01

    In this study, we consider the optimal portfolio selection problem with liquidity limits. A portfolio selection model is proposed in which the risky asset price is driven by the process based on non-extensive statistical mechanics instead of the classic Wiener process. Using dynamic programming and Lagrange multiplier methods, we obtain the optimal policy and value function. Moreover, the numerical results indicate that this model is considerably different from the model based on the classic Wiener process, the optimal strategy is affected by the non-extensive parameter q, the increase in the investment in the risky asset is faster at a larger parameter q and the increase in wealth is similar.

  2. Statistical analysis of traversal behavior under different types of traffic lights

    Science.gov (United States)

    Wang, Boran; Wang, Ziyang; Li, Zhiyin

    2017-12-01

    According to the video observation, it is found that the traffic signal type signal has a significant effect on the illegal crossing behavior of pedestrians at the intersection. Through the method of statistical analysis and variance analysis, the difference between the violation rate and the waiting position of pedestrians at different intersecting lights is compared, and the influence of traffic signal type on pedestrian crossing behavior is evaluated. The results show that the violation rate of the intersection of the static pedestrian lights is significantly higher than that of the countdown signal lights. There are significant differences in the waiting position of the intersection of different signal lights.

  3. FADTTSter: accelerating hypothesis testing with functional analysis of diffusion tensor tract statistics

    Science.gov (United States)

    Noel, Jean; Prieto, Juan C.; Styner, Martin

    2017-03-01

    Functional Analysis of Diffusion Tensor Tract Statistics (FADTTS) is a toolbox for analysis of white matter (WM) fiber tracts. It allows associating diffusion properties along major WM bundles with a set of covariates of interest, such as age, diagnostic status and gender, and the structure of the variability of these WM tract properties. However, to use this toolbox, a user must have an intermediate knowledge in scripting languages (MATLAB). FADTTSter was created to overcome this issue and make the statistical analysis accessible to any non-technical researcher. FADTTSter is actively being used by researchers at the University of North Carolina. FADTTSter guides non-technical users through a series of steps including quality control of subjects and fibers in order to setup the necessary parameters to run FADTTS. Additionally, FADTTSter implements interactive charts for FADTTS' outputs. This interactive chart enhances the researcher experience and facilitates the analysis of the results. FADTTSter's motivation is to improve usability and provide a new analysis tool to the community that complements FADTTS. Ultimately, by enabling FADTTS to a broader audience, FADTTSter seeks to accelerate hypothesis testing in neuroimaging studies involving heterogeneous clinical data and diffusion tensor imaging. This work is submitted to the Biomedical Applications in Molecular, Structural, and Functional Imaging conference. The source code of this application is available in NITRC.

  4. Using the Δ3 statistic to test for missed levels in mixed sequence neutron resonance data

    International Nuclear Information System (INIS)

    Mulhall, Declan

    2009-01-01

    The Δ 3 (L) statistic is studied as a tool to detect missing levels in the neutron resonance data where two sequences are present. These systems are problematic because there is no level repulsion, and the resonances can be too close to resolve. Δ 3 (L) is a measure of the fluctuations in the number of levels in an interval of length L on the energy axis. The method used is tested on ensembles of mixed Gaussian orthogonal ensemble spectra, with a known fraction of levels (x%) randomly depleted, and can accurately return x. The accuracy of the method as a function of spectrum size is established. The method is used on neutron resonance data for 11 isotopes with either s-wave neutrons on odd-A isotopes, or p-wave neutrons on even-A isotopes. The method compares favorably with a maximum likelihood method applied to the level spacing distribution. Nuclear data ensembles were made from 20 isotopes in total, and their Δ 3 (L) statistics are discussed in the context of random matrix theory.

  5. Integrating Symbolic and Statistical Methods for Testing Intelligent Systems Applications to Machine Learning and Computer Vision

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Sumit Kumar [University of Central Florida, Orlando; Pullum, Laura L [ORNL; Ramanathan, Arvind [ORNL

    2016-01-01

    Embedded intelligent systems ranging from tiny im- plantable biomedical devices to large swarms of autonomous un- manned aerial systems are becoming pervasive in our daily lives. While we depend on the flawless functioning of such intelligent systems, and often take their behavioral correctness and safety for granted, it is notoriously difficult to generate test cases that expose subtle errors in the implementations of machine learning algorithms. Hence, the validation of intelligent systems is usually achieved by studying their behavior on representative data sets, using methods such as cross-validation and bootstrapping.In this paper, we present a new testing methodology for studying the correctness of intelligent systems. Our approach uses symbolic decision procedures coupled with statistical hypothesis testing to. We also use our algorithm to analyze the robustness of a human detection algorithm built using the OpenCV open-source computer vision library. We show that the human detection implementation can fail to detect humans in perturbed video frames even when the perturbations are so small that the corresponding frames look identical to the naked eye.

  6. Parameter estimation and statistical test of geographically weighted bivariate Poisson inverse Gaussian regression models

    Science.gov (United States)

    Amalia, Junita; Purhadi, Otok, Bambang Widjanarko

    2017-11-01

    Poisson distribution is a discrete distribution with count data as the random variables and it has one parameter defines both mean and variance. Poisson regression assumes mean and variance should be same (equidispersion). Nonetheless, some case of the count data unsatisfied this assumption because variance exceeds mean (over-dispersion). The ignorance of over-dispersion causes underestimates in standard error. Furthermore, it causes incorrect decision in the statistical test. Previously, paired count data has a correlation and it has bivariate Poisson distribution. If there is over-dispersion, modeling paired count data is not sufficient with simple bivariate Poisson regression. Bivariate Poisson Inverse Gaussian Regression (BPIGR) model is mix Poisson regression for modeling paired count data within over-dispersion. BPIGR model produces a global model for all locations. In another hand, each location has different geographic conditions, social, cultural and economic so that Geographically Weighted Regression (GWR) is needed. The weighting function of each location in GWR generates a different local model. Geographically Weighted Bivariate Poisson Inverse Gaussian Regression (GWBPIGR) model is used to solve over-dispersion and to generate local models. Parameter estimation of GWBPIGR model obtained by Maximum Likelihood Estimation (MLE) method. Meanwhile, hypothesis testing of GWBPIGR model acquired by Maximum Likelihood Ratio Test (MLRT) method.

  7. An omnibus likelihood test statistic and its factorization for change detection in time series of polarimetric SAR data

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Conradsen, Knut; Skriver, Henning

    2016-01-01

    Based on an omnibus likelihood ratio test statistic for the equality of several variance-covariance matrices following the complex Wishart distribution with an associated p-value and a factorization of this test statistic, change analysis in a short sequence of multilook, polarimetric SAR data...... in the covariance matrix representation is carried out. The omnibus test statistic and its factorization detect if and when change(s) occur. The technique is demonstrated on airborne EMISAR L-band data but may be applied to Sentinel-1, Cosmo-SkyMed, TerraSAR-X, ALOS and RadarSat-2 or other dual- and quad...

  8. Change detection in a time series of polarimetric SAR data by an omnibus test statistic and its factorization

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Conradsen, Knut; Skriver, Henning

    2016-01-01

    Based on an omnibus likelihood ratio test statistic for the equality of several variance-covariance matrices following the complex Wishart distribution with an associated p-value and a factorization of this test statistic, change analysis in a short sequence of multilook, polarimetric SAR data...... in the covariance matrix representation is carried out. The omnibus test statistic and its factorization detect if and when change(s) occur. The technique is demonstrated on airborne EMISAR L-band data but may be applied to Sentinel-1, Cosmo-SkyMed, TerraSAR-X, ALOS and RadarSat-2 or other dual- and quad...

  9. Orthodontic brackets removal under shear and tensile bond strength resistance tests - a comparative test between light sources

    Science.gov (United States)

    Silva, P. C. G.; Porto-Neto, S. T.; Lizarelli, R. F. Z.; Bagnato, V. S.

    2008-03-01

    We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased.

  10. Orthodontic brackets removal under shear and tensile bond strength resistance tests – a comparative test between light sources

    International Nuclear Information System (INIS)

    Silva, P C G; Porto-Neto, S T; Lizarelli, R F Z; Bagnato, V S

    2008-01-01

    We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased

  11. Investigating the Investigative Task: Testing for Skewness--An Investigation of Different Test Statistics and Their Power to Detect Skewness

    Science.gov (United States)

    Tabor, Josh

    2010-01-01

    On the 2009 AP[c] Statistics Exam, students were asked to create a statistic to measure skewness in a distribution. This paper explores several of the most popular student responses and evaluates which statistic performs best when sampling from various skewed populations. (Contains 8 figures, 3 tables, and 4 footnotes.)

  12. DWPF Sample Vial Insert Study-Statistical Analysis of DWPF Mock-Up Test Data

    Energy Technology Data Exchange (ETDEWEB)

    Harris, S.P. [Westinghouse Savannah River Company, AIKEN, SC (United States)

    1997-09-18

    This report is prepared as part of Technical/QA Task Plan WSRC-RP-97-351 which was issued in response to Technical Task Request HLW/DWPF/TTR-970132 submitted by DWPF. Presented in this report is a statistical analysis of DWPF Mock-up test data for evaluation of two new analytical methods which use insert samples from the existing HydragardTM sampler. The first is a new hydrofluoric acid based method called the Cold Chemical Method (Cold Chem) and the second is a modified fusion method.Either new DWPF analytical method could result in a two to three fold improvement in sample analysis time.Both new methods use the existing HydragardTM sampler to collect a smaller insert sample from the process sampling system. The insert testing methodology applies to the DWPF Slurry Mix Evaporator (SME) and the Melter Feed Tank (MFT) samples.The insert sample is named after the initial trials which placed the container inside the sample (peanut) vials. Samples in small 3 ml containers (Inserts) are analyzed by either the cold chemical method or a modified fusion method. The current analytical method uses a HydragardTM sample station to obtain nearly full 15 ml peanut vials. The samples are prepared by a multi-step process for Inductively Coupled Plasma (ICP) analysis by drying, vitrification, grinding and finally dissolution by either mixed acid or fusion. In contrast, the insert sample is placed directly in the dissolution vessel, thus eliminating the drying, vitrification and grinding operations for the Cold chem method. Although the modified fusion still requires drying and calcine conversion, the process is rapid due to the decreased sample size and that no vitrification step is required.A slurry feed simulant material was acquired from the TNX pilot facility from the test run designated as PX-7.The Mock-up test data were gathered on the basis of a statistical design presented in SRT-SCS-97004 (Rev. 0). Simulant PX-7 samples were taken in the DWPF Analytical Cell Mock

  13. DWPF Sample Vial Insert Study-Statistical Analysis of DWPF Mock-Up Test Data

    International Nuclear Information System (INIS)

    Harris, S.P.

    1997-01-01

    This report is prepared as part of Technical/QA Task Plan WSRC-RP-97-351 which was issued in response to Technical Task Request HLW/DWPF/TTR-970132 submitted by DWPF. Presented in this report is a statistical analysis of DWPF Mock-up test data for evaluation of two new analytical methods which use insert samples from the existing HydragardTM sampler. The first is a new hydrofluoric acid based method called the Cold Chemical Method (Cold Chem) and the second is a modified fusion method.Both new methods use the existing HydragardTM sampler to collect a smaller insert sample from the process sampling system. The insert testing methodology applies to the DWPF Slurry Mix Evaporator (SME) and the Melter Feed Tank (MFT) samples. Samples in small 3 ml containers (Inserts) are analyzed by either the cold chemical method or a modified fusion method. The current analytical method uses a HydragardTM sample station to obtain nearly full 15 ml peanut vials. The samples are prepared by a multi-step process for Inductively Coupled Plasma (ICP) analysis by drying, vitrification, grinding and finally dissolution by either mixed acid or fusion. In contrast, the insert sample is placed directly in the dissolution vessel, thus eliminating the drying, vitrification and grinding operations for the Cold chem method. Although the modified fusion still requires drying and calcine conversion, the process is rapid due to the decreased sample size and that no vitrification step is required.A slurry feed simulant material was acquired from the TNX pilot facility from the test run designated as PX-7.The Mock-up test data were gathered on the basis of a statistical design presented in SRT-SCS-97004 (Rev. 0). Simulant PX-7 samples were taken in the DWPF Analytical Cell Mock-up Facility using 3 ml inserts and 15 ml peanut vials. A number of the insert samples were analyzed by Cold Chem and compared with full peanut vial samples analyzed by the current methods. The remaining inserts were analyzed by

  14. Using Cochran's Z Statistic to Test the Kernel-Smoothed Item Response Function Differences between Focal and Reference Groups

    Science.gov (United States)

    Zheng, Yinggan; Gierl, Mark J.; Cui, Ying

    2010-01-01

    This study combined the kernel smoothing procedure and a nonparametric differential item functioning statistic--Cochran's Z--to statistically test the difference between the kernel-smoothed item response functions for reference and focal groups. Simulation studies were conducted to investigate the Type I error and power of the proposed…

  15. Assessment of metals bioavailability to vegetables under field conditions using DGT, single extractions and multivariate statistics

    Science.gov (United States)

    2012-01-01

    Background The metals bioavailability in soils is commonly assessed by chemical extractions; however a generally accepted method is not yet established. In this study, the effectiveness of Diffusive Gradients in Thin-films (DGT) technique and single extractions in the assessment of metals bioaccumulation in vegetables, and the influence of soil parameters on phytoavailability were evaluated using multivariate statistics. Soil and plants grown in vegetable gardens from mining-affected rural areas, NW Romania, were collected and analysed. Results Pseudo-total metal content of Cu, Zn and Cd in soil ranged between 17.3-146 mg kg-1, 141–833 mg kg-1 and 0.15-2.05 mg kg-1, respectively, showing enriched contents of these elements. High degrees of metals extractability in 1M HCl and even in 1M NH4Cl were observed. Despite the relatively high total metal concentrations in soil, those found in vegetables were comparable to values typically reported for agricultural crops, probably due to the low concentrations of metals in soil solution (Csoln) and low effective concentrations (CE), assessed by DGT technique. Among the analysed vegetables, the highest metal concentrations were found in carrots roots. By applying multivariate statistics, it was found that CE, Csoln and extraction in 1M NH4Cl, were better predictors for metals bioavailability than the acid extractions applied in this study. Copper transfer to vegetables was strongly influenced by soil organic carbon (OC) and cation exchange capacity (CEC), while pH had a higher influence on Cd transfer from soil to plants. Conclusions The results showed that DGT can be used for general evaluation of the risks associated to soil contamination with Cu, Zn and Cd in field conditions. Although quantitative information on metals transfer from soil to vegetables was not observed. PMID:23079133

  16. Predicting fracture of mortar beams under three-point bending using non-extensive statistical modeling of electric emissions

    Science.gov (United States)

    Stergiopoulos, Ch.; Stavrakas, I.; Triantis, D.; Vallianatos, F.; Stonham, J.

    2015-02-01

    Weak electric signals termed as 'Pressure Stimulated Currents, PSC' are generated and detected while cement based materials are found under mechanical load, related to the creation of cracks and the consequent evolution of cracks' network in the bulk of the specimen. During the experiment a set of cement mortar beams of rectangular cross-section were subjected to Three-Point Bending (3PB). For each one of the specimens an abrupt mechanical load step was applied, increased from the low load level (Lo) to a high final value (Lh) , where Lh was different for each specimen and it was maintained constant for long time. The temporal behavior of the recorded PSC show that during the load increase a spike-like PSC emission was recorded and consequently a relaxation of the PSC, after reaching its final value, follows. The relaxation process of the PSC was studied using non-extensive statistical physics (NESP) based on Tsallis entropy equation. The behavior of the Tsallis q parameter was studied in relaxation PSCs in order to investigate its potential use as an index for monitoring the crack evolution process with a potential use in non-destructive laboratory testing of cement-based specimens of unknown internal damage level. The dependence of the q-parameter on the Lh (when Lh <0.8Lf), where Lf represents the 3PB strength of the specimen, shows an increase on the q value when the specimens are subjected to gradually higher bending loadings and reaches a maximum value close to 1.4 when the applied Lh becomes higher than 0.8Lf. While the applied Lh becomes higher than 0.9Lf the value of the q-parameter gradually decreases. This analysis of the experimental data manifests that the value of the entropic index q obtains a characteristic decrease while reaching the ultimate strength of the specimen, and thus could be used as a forerunner of the expected failure.

  17. Heteroscedastic Tests Statistics for One-Way Analysis of Variance: The Trimmed Means and Hall's Transformation Conjunction

    Science.gov (United States)

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2005-01-01

    To deal with nonnormal and heterogeneous data for the one-way fixed effect analysis of variance model, the authors adopted a trimmed means method in conjunction with Hall's invertible transformation into a heteroscedastic test statistic (Alexander-Govern test or Welch test). The results of simulation experiments showed that the proposed technique…

  18. Variability in source sediment contributions by applying different statistic test for a Pyrenean catchment.

    Science.gov (United States)

    Palazón, L; Navas, A

    2017-06-01

    Information on sediment contribution and transport dynamics from the contributing catchments is needed to develop management plans to tackle environmental problems related with effects of fine sediment as reservoir siltation. In this respect, the fingerprinting technique is an indirect technique known to be valuable and effective for sediment source identification in river catchments. Large variability in sediment delivery was found in previous studies in the Barasona catchment (1509 km 2 , Central Spanish Pyrenees). Simulation results with SWAT and fingerprinting approaches identified badlands and agricultural uses as the main contributors to sediment supply in the reservoir. In this study the Kruskal-Wallis H-test and (3) principal components analysis. Source contribution results were different between assessed options with the greatest differences observed for option using #3, including the two step process: principal components analysis and discriminant function analysis. The characteristics of the solutions by the applied mixing model and the conceptual understanding of the catchment showed that the most reliable solution was achieved using #2, the two step process of Kruskal-Wallis H-test and discriminant function analysis. The assessment showed the importance of the statistical procedure used to define the optimum composite fingerprint for sediment fingerprinting applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Statistical testing of the full-range leadership theory in nursing.

    Science.gov (United States)

    Kanste, Outi; Kääriäinen, Maria; Kyngäs, Helvi

    2009-12-01

    The aim of this study is to test statistically the structure of the full-range leadership theory in nursing. The data were gathered by postal questionnaires from nurses and nurse leaders working in healthcare organizations in Finland. A follow-up study was performed 1 year later. The sample consisted of 601 nurses and nurse leaders, and the follow-up study had 78 respondents. Theory was tested through structural equation modelling, standard regression analysis and two-way anova. Rewarding transformational leadership seems to promote and passive laissez-faire leadership to reduce willingness to exert extra effort, perceptions of leader effectiveness and satisfaction with the leader. Active management-by-exception seems to reduce willingness to exert extra effort and perception of leader effectiveness. Rewarding transformational leadership remained as a strong explanatory factor of all outcome variables measured 1 year later. The data supported the main structure of the full-range leadership theory, lending support to the universal nature of the theory.

  20. Statistical methods for the analysis of a screening test for chronic beryllium disease

    Energy Technology Data Exchange (ETDEWEB)

    Frome, E.L.; Neubert, R.L. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section; Smith, M.H.; Littlefield, L.G.; Colyer, S.P. [Oak Ridge Inst. for Science and Education, TN (United States). Medical Sciences Div.

    1994-10-01

    The lymphocyte proliferation test (LPT) is a noninvasive screening procedure used to identify persons who may have chronic beryllium disease. A practical problem in the analysis of LPT well counts is the occurrence of outlying data values (approximately 7% of the time). A log-linear regression model is used to describe the expected well counts for each set of test conditions. The variance of the well counts is proportional to the square of the expected counts, and two resistant regression methods are used to estimate the parameters of interest. The first approach uses least absolute values (LAV) on the log of the well counts to estimate beryllium stimulation indices (SIs) and the coefficient of variation. The second approach uses a resistant regression version of maximum quasi-likelihood estimation. A major advantage of the resistant regression methods is that it is not necessary to identify and delete outliers. These two new methods for the statistical analysis of the LPT data and the outlier rejection method that is currently being used are applied to 173 LPT assays. The authors strongly recommend the LAV method for routine analysis of the LPT.

  1. Possible Solution to Publication Bias Through Bayesian Statistics, Including Proper Null Hypothesis Testing

    NARCIS (Netherlands)

    Konijn, Elly A.; van de Schoot, Rens; Winter, Sonja D.; Ferguson, Christopher J.

    2015-01-01

    The present paper argues that an important cause of publication bias resides in traditional frequentist statistics forcing binary decisions. An alternative approach through Bayesian statistics provides various degrees of support for any hypothesis allowing balanced decisions and proper null

  2. Multileaf collimator performance monitoring and improvement using semiautomated quality control testing and statistical process control

    International Nuclear Information System (INIS)

    Létourneau, Daniel; McNiven, Andrea; Keller, Harald; Wang, An; Amin, Md Nurul; Pearce, Jim; Norrlinger, Bernhard; Jaffray, David A.

    2014-01-01

    Purpose: High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process control tools, was developed. The MLC performance monitoring system was used for almost a year on two commercially available MLC models. Control charts were used to establish MLC performance and assess test frequency required to achieve a given level of performance. MLC-related interlocks and servicing events were recorded during the monitoring period and were investigated as indicators of MLC performance variations. Methods: The QC test developed as part of the MLC performance monitoring system uses 2D megavoltage images (acquired using an electronic portal imaging device) of 23 fields to determine the location of the leaves with respect to the radiation isocenter. The precision of the MLC performance monitoring QC test and the MLC itself was assessed by detecting the MLC leaf positions on 127 megavoltage images of a static field. After initial calibration, the MLC performance monitoring QC test was performed 3–4 times/week over a period of 10–11 months to monitor positional accuracy of individual leaves for two different MLC models. Analysis of test results was performed using individuals control charts per leaf with control limits computed based on the measurements as well as two sets of specifications of ±0.5 and ±1 mm. Out-of-specification and out-of-control leaves were automatically flagged by the monitoring system and reviewed monthly by physicists. MLC-related interlocks reported by the linear accelerator and servicing events were recorded to help identify potential causes of nonrandom MLC leaf positioning variations. Results: The precision of the MLC performance monitoring QC test and the MLC itself was within ±0.22 mm for most MLC leaves

  3. Multileaf collimator performance monitoring and improvement using semiautomated quality control testing and statistical process control.

    Science.gov (United States)

    Létourneau, Daniel; Wang, An; Amin, Md Nurul; Pearce, Jim; McNiven, Andrea; Keller, Harald; Norrlinger, Bernhard; Jaffray, David A

    2014-12-01

    High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process control tools, was developed. The MLC performance monitoring system was used for almost a year on two commercially available MLC models. Control charts were used to establish MLC performance and assess test frequency required to achieve a given level of performance. MLC-related interlocks and servicing events were recorded during the monitoring period and were investigated as indicators of MLC performance variations. The QC test developed as part of the MLC performance monitoring system uses 2D megavoltage images (acquired using an electronic portal imaging device) of 23 fields to determine the location of the leaves with respect to the radiation isocenter. The precision of the MLC performance monitoring QC test and the MLC itself was assessed by detecting the MLC leaf positions on 127 megavoltage images of a static field. After initial calibration, the MLC performance monitoring QC test was performed 3-4 times/week over a period of 10-11 months to monitor positional accuracy of individual leaves for two different MLC models. Analysis of test results was performed using individuals control charts per leaf with control limits computed based on the measurements as well as two sets of specifications of ± 0.5 and ± 1 mm. Out-of-specification and out-of-control leaves were automatically flagged by the monitoring system and reviewed monthly by physicists. MLC-related interlocks reported by the linear accelerator and servicing events were recorded to help identify potential causes of nonrandom MLC leaf positioning variations. The precision of the MLC performance monitoring QC test and the MLC itself was within ± 0.22 mm for most MLC leaves and the majority of the

  4. Electrostatic induction under the Tanashi test transmission line

    Energy Technology Data Exchange (ETDEWEB)

    Kitani, Y; Yokata, S

    1964-06-01

    Experimental results are given on the electrostatic voltage induced in small and medium-sized motorcars under the Tanashi 800 kV Test Transmission Line, which is of horizontal arrangement, 200 m span, four bundle conductors and average height of 13.52 m. The induced voltage was measured between 1600 and 3000 V under the line voltage of 520 kV. The voltage and current were measured with four kinds of model motorcars in air and water, and results of the measurements are compared with those of actual measurements with good agreements. The values of capacity and leakage resistance, whose parallel circuit was considered to represent an equivalent circuit of the motorcar, were measured with a Maxwell-Wien bridge at frequencies between 30 and 1000 c/s. It was found that the values at 60 c/s were measured to be approximately six or seven times higher than its values at 1000 c/s, and that new tires have higher conductivities than the old ones, reducing the electrostatic induction voltage by a large amount.

  5. A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated

    Directory of Open Access Journals (Sweden)

    Elżbieta Sandurska

    2016-12-01

    Full Text Available Introduction: Application of statistical software typically does not require extensive statistical knowledge, allowing to easily perform even complex analyses. Consequently, test selection criteria and important assumptions may be easily overlooked or given insufficient consideration. In such cases, the results may likely lead to wrong conclusions. Aim: To discuss issues related to assumption violations in the case of Student's t-test and one-way ANOVA, two parametric tests frequently used in the field of sports science, and to recommend solutions. Description of the state of knowledge: Student's t-test and ANOVA are parametric tests, and therefore some of the assumptions that need to be satisfied include normal distribution of the data and homogeneity of variances in groups. If the assumptions are violated, the original design of the test is impaired, and the test may then be compromised giving spurious results. A simple method to normalize the data and to stabilize the variance is to use transformations. If such approach fails, a good alternative to consider is a nonparametric test, such as Mann-Whitney, the Kruskal-Wallis or Wilcoxon signed-rank tests. Summary: Thorough verification of the parametric tests assumptions allows for correct selection of statistical tools, which is the basis of well-grounded statistical analysis. With a few simple rules, testing patterns in the data characteristic for the study of sports science comes down to a straightforward procedure.

  6. A statistical characterization of the finger tapping test: modeling, estimation, and applications.

    Science.gov (United States)

    Austin, Daniel; McNames, James; Klein, Krystal; Jimison, Holly; Pavel, Misha

    2015-03-01

    Sensory-motor performance is indicative of both cognitive and physical function. The Halstead-Reitan finger tapping test is a measure of sensory-motor speed commonly used to assess function as part of a neuropsychological evaluation. Despite the widespread use of this test, the underlying motor and cognitive processes driving tapping behavior during the test are not well characterized or understood. This lack of understanding may make clinical inferences from test results about health or disease state less accurate because important aspects of the task such as variability or fatigue are unmeasured. To overcome these limitations, we enhanced the tapper with a sensor that enables us to more fully characterize all the aspects of tapping. This modification enabled us to decompose the tapping performance into six component phases and represent each phase with a set of parameters having clear functional interpretation. This results in a set of 29 total parameters for each trial, including change in tapping over time, and trial-to-trial and tap-to-tap variability. These parameters can be used to more precisely link different aspects of cognition or motor function to tapping behavior. We demonstrate the benefits of this new instrument with a simple hypothesis-driven trial comparing single and dual-task tapping.

  7. Testing of a "smart-pebble" for measuring particle transport statistics

    Science.gov (United States)

    Kitsikoudis, Vasileios; Avgeris, Loukas; Valyrakis, Manousos

    2017-04-01

    This paper presents preliminary results from novel experiments aiming to assess coarse sediment transport statistics for a range of transport conditions, via the use of an innovative "smart-pebble" device. This device is a waterproof sphere, which has 7 cm diameter and is equipped with a number of sensors that provide information about the velocity, acceleration and positioning of the "smart-pebble" within the flow field. A series of specifically designed experiments are carried out to monitor the entrainment of a "smart-pebble" for fully developed, uniform, turbulent flow conditions over a hydraulically rough bed. Specifically, the bed surface is configured to three sections, each of them consisting of well packed glass beads of slightly increasing size at the downstream direction. The first section has a streamwise length of L1=150 cm and beads size of D1=15 mm, the second section has a length of L2=85 cm and beads size of D2=22 mm, and the third bed section has a length of L3=55 cm and beads size of D3=25.4 mm. Two cameras monitor the area of interest to provide additional information regarding the "smart-pebble" movement. Three-dimensional flow measurements are obtained with the aid of an acoustic Doppler velocimeter along a measurement grid to assess the flow forcing field. A wide range of flow rates near and above the threshold of entrainment is tested, while using four distinct densities for the "smart-pebble", which can affect its transport speed and total momentum. The acquired data are analyzed to derive Lagrangian transport statistics and the implications of such an important experiment for the transport of particles by rolling are discussed. The flow conditions for the initiation of motion, particle accelerations and equilibrium particle velocities (translating into transport rates), statistics of particle impact and its motion, can be extracted from the acquired data, which can be further compared to develop meaningful insights for sediment transport

  8. A Lagrange multiplier-type test for idiosyncratic unit roots in the exact factor model under misspecification

    NARCIS (Netherlands)

    Zhou, X.; Solberger, M.

    2013-01-01

    We consider an exact factor model and derive a Lagrange multiplier-type test for unit roots in the idiosyncratic components. The asymptotic distribution of the statistic is derived under the misspecification that the differenced factors are white noise. We prove that the asymptotic distribution is

  9. The Bayesian Score Statistic

    NARCIS (Netherlands)

    Kleibergen, F.R.; Kleijn, R.; Paap, R.

    2000-01-01

    We propose a novel Bayesian test under a (noninformative) Jeffreys'priorspecification. We check whether the fixed scalar value of the so-calledBayesian Score Statistic (BSS) under the null hypothesis is aplausiblerealization from its known and standardized distribution under thealternative. Unlike

  10. Hyper-binding only apparent under fully implicit test conditions.

    Science.gov (United States)

    Campbell, Karen L; Hasher, Lynn

    2018-02-01

    We have previously shown that older adults hyper-bind, or form more extraneous associations than younger adults. For instance, when asked to perform a 1-back task on pictures superimposed with distracting words, older adults inadvertently form associations between target-distractor pairs and implicitly transfer these associations to a later paired associate learning task (showing a boost in relearning of preserved over disrupted pairs). We have argued that younger adults are better at suppressing the distracting words and thus, do not form these extraneous associations in the first place. However, an alternative explanation is that younger adults simply fail to access these associations during relearning, possibly because of their superior ability to form boundaries between episodes or shift mental contexts between tasks. In this study, we aimed to both replicate this original implicit transfer effect in older adults and to test whether younger adults show evidence of hyper-binding when informed about the relevance of past information. Our results suggest that regardless of the test conditions, younger adults do not hyper-bind. In contrast, older adults showed hyper-binding under (standard) implicit instructions, but not when made aware of a connection between tasks. These results replicate the original hyper-binding effect and reiterate its implicit nature. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  11. Statistical evaluation of physical examinations conducted under atomic bomb survivors medical treatment law Nagasaki

    Energy Technology Data Exchange (ETDEWEB)

    Ohri, Shigehisa; Shimada, Daisaburo; Ishida, Morthiro; Onishi, Shigeyuki

    1961-09-19

    An evaluation was made of the reliability and validity of the information obtained by the first examination completed under the ABSMTL. Results of the analysis show clearly that the materials hardly can be utilized for studying the relationship between findings obtained from the medical examination and distance from the hypocenter. From the standpoint of clinical medicine, the lack of exactness in the examinations may be a major difficulty. However, as long as the degree of inexactness of the medical examinations is distributed equally to all sample members, comparison of the findings may be made within the limits of their accuracy. 4 references, 1 figure, 3 tables.

  12. Post-test investigation result on the WWER-1000 fuel tested under severe accident conditions

    International Nuclear Information System (INIS)

    Goryachev, A.; Shtuckert, Yu.; Zwir, E.; Stupina, L.

    1996-01-01

    The model bundle of WWER-type were tested under SFD condition in the out-of-pile CORA installation. The objective of the test was to provide an information on the WWER-type fuel bundles behaviour under severe fuel damage accident conditions. Also it was assumed to compare the WWER-type bundle damage mechanisms with these experienced in the PWR-type bundle tests with aim to confirm a possibility to use the various code systems, worked our for PWR as applied to WWER. In order to ensure the possibility of the comparison of the calculated core degradation parameters with the real state of the tested bundle, some parameters have been measured on the bundle cross-sections under examination. Quantitative parameters of the bundle degradation have been evaluated by digital image processing of the bundle cross-sections. The obtained results are shown together with corresponding results obtained by the other participants of this investigation. (author). 3 refs, 13 figs

  13. A comprehensive statistical classifier of foci in the cell transformation assay for carcinogenicity testing.

    Science.gov (United States)

    Callegaro, Giulia; Malkoc, Kasja; Corvi, Raffaella; Urani, Chiara; Stefanini, Federico M

    2017-12-01

    The identification of the carcinogenic risk of chemicals is currently mainly based on animal studies. The in vitro Cell Transformation Assays (CTAs) are a promising alternative to be considered in an integrated approach. CTAs measure the induction of foci of transformed cells. CTAs model key stages of the in vivo neoplastic process and are able to detect both genotoxic and some non-genotoxic compounds, being the only in vitro method able to deal with the latter. Despite their favorable features, CTAs can be further improved, especially reducing the possible subjectivity arising from the last phase of the protocol, namely visual scoring of foci using coded morphological features. By taking advantage of digital image analysis, the aim of our work is to translate morphological features into statistical descriptors of foci images, and to use them to mimic the classification performances of the visual scorer to discriminate between transformed and non-transformed foci. Here we present a classifier based on five descriptors trained on a dataset of 1364 foci, obtained with different compounds and concentrations. Our classifier showed accuracy, sensitivity and specificity equal to 0.77 and an area under the curve (AUC) of 0.84. The presented classifier outperforms a previously published model. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Pipe rupture test results; 6 in. pipe whip test under BWR LOCA conditions

    International Nuclear Information System (INIS)

    Kurihara, Ryoichi; Yano, Toshikazu; Ueda, Shuzo; Isozaki, Toshikuni; Miyazaki, Noriyuki; Kato, Rokuro; Miyazono, Shohachiro

    1983-02-01

    A series of pipe rupture tests has been performed in JAERI to demonstrate the safety of the primary coolant circuits in the event of pipe rupture, in nuclear power plants. The present report summarizes the results of 6 in. pipe whip tests (RUN 5605, 5606), under BWR LOCA conditions (285 0 C, 6.8 MPa), which were performed in August, 1981. The test pipe is made of Type 304 stainless steel and its outer diameter is 6 in. and its thickness is 11.1 mm. The restraints are made of Type 304 stainless steel and its diameter is 16.0 mm. Two restraints were set on the restraint support with clearance of 100 mm. Overhang length was varied as the parameter in these tests and was 300 mm or 700 mm. The following results are obtained. (1) The deformations of a pipe and restraints are limited effectively by shorter overhang length of 300. However, they become larger when the overhang length is 700 mm, and the pipe deforms especially at the setting point of restraints. (2) Velocity at the free end of pipe becomes about 30 m/sec just after the break. However, velocity at the setting point of restraint becomes about only 4 m/sec just after the break. (3) It seems from the comparison between the 4 in. tests and 6 in. tests that the maximum restraint force of 6 in. tests is about two times as large as that of 4 in. tests. (author)

  15. Pipe rupture test results: 4-inch pipe whip tests under PWR LOCA conditions

    International Nuclear Information System (INIS)

    Miyazaki, Noriyuki; Ueda, Shuzo; Isozaki, Toshikuni; Kato, Rokuro; Kurihara, Ryoichi; Yano, Toshikazu; Miyazono, Shohachiro

    1982-09-01

    This report summarizes the results of 4-inch pipe whip tests (RUN No. 5506, 5507, 5508 and 5604) under the PWR LOCA conditions. The dynamic behaviors of the test pipe and restraints were studied in the tests. In the tests, the gap between the test pipe and the restraints was kept at the constant value of 8.85 mm and the overhang length was varied from 250 mm to 650 mm. The dynamic behaviors of the test pipe and the restraint were made clear by the outputs of strain gages and the measurements of residual deformations. The data of water hammer in subcooled water were also obtained by the pressure transducers mounted on the test pipe. The main conclusions obtained from the tests are as follows. (1) The whipping of pipe can be prevented more effectively as the overhang length becomes shorter. (2) The load acting on the restraint-support structure becomes larger as the overhang length becomes shorter. (3) The restraint farther from the break location does not limit the pipe movement except for the first impact when the overhang length is long. (4) The ultimate moment M sub(u) of the pipe at the restraint location can be used to predict the plastic collapse of the whipping pipe. (5) The restraints slide along the pipe axis and are subjected to bending moment, when the overhang length is long. (author)

  16. Statistical mechanics of fluids under internal constraints: Rigorous results for the one-dimensional hard rod fluid

    International Nuclear Information System (INIS)

    Corti, D.S.; Debenedetti, P.G.

    1998-01-01

    The rigorous statistical mechanics of metastability requires the imposition of internal constraints that prevent access to regions of phase space corresponding to inhomogeneous states. We derive exactly the Helmholtz energy and equation of state of the one-dimensional hard rod fluid under the influence of an internal constraint that places an upper bound on the distance between nearest-neighbor rods. This type of constraint is relevant to the suppression of boiling in a superheated liquid. We determine the effects of this constraint upon the thermophysical properties and internal structure of the hard rod fluid. By adding an infinitely weak and infinitely long-ranged attractive potential to the hard core, the fluid exhibits a first-order vapor-liquid transition. We determine exactly the equation of state of the one-dimensional superheated liquid and show that it exhibits metastable phase equilibrium. We also derive statistical mechanical relations for the equation of state of a fluid under the action of arbitrary constraints, and show the connection between the statistical mechanics of constrained and unconstrained ensembles. copyright 1998 The American Physical Society

  17. A practical model-based statistical approach for generating functional test cases: application in the automotive industry

    OpenAIRE

    Awédikian , Roy; Yannou , Bernard

    2012-01-01

    International audience; With the growing complexity of industrial software applications, industrials are looking for efficient and practical methods to validate the software. This paper develops a model-based statistical testing approach that automatically generates online and offline test cases for embedded software. It discusses an integrated framework that combines solutions for three major software testing research questions: (i) how to select test inputs; (ii) how to predict the expected...

  18. A method to identify dependencies between organizational factors using statistical independence test

    International Nuclear Information System (INIS)

    Kim, Y.; Chung, C.H.; Kim, C.; Jae, M.; Jung, J.H.

    2004-01-01

    A considerable number of studies on organizational factors in nuclear power plants have been made especially in recent years, most of which have assumed organizational factors to be independent. However, since organizational factors characterize the organization in terms of safety and efficiency etc. and there would be some factors that have close relations between them. Therefore, from whatever point of view, if we want to identify the characteristics of an organization, the dependence relationships should be considered to get an accurate result. In this study the organization of a reference nuclear power plant in Korea was analyzed for the trip cases of that plant using 20 organizational factors that Jacobs and Haber had suggested: 1) coordination of work, 2) formalization, 3) organizational knowledge, 4) roles and responsibilities, 5) external communication, 6) inter-department communications, 7) intra-departmental communications, 8) organizational culture, 9) ownership, 10) safety culture, 11) time urgency, 12) centralization, 13) goal prioritization, 14) organizational learning, 15) problem identification, 16) resource allocation, 17) performance evaluation, 18) personnel selection, 19) technical knowledge, and 20) training. By utilizing the results of the analysis, a method to identify the dependence relationships between organizational factors is presented. The statistical independence test for the analysis result of the trip cases is adopted to reveal dependencies. This method is geared to the needs to utilize many kinds of data that has been obtained as the operating years of nuclear power plants increase, and more reliable dependence relations may be obtained by using these abundant data

  19. The complete linkage disequilibrium test: a test that points to causative mutations underlying quantitative traits

    Directory of Open Access Journals (Sweden)

    Uleberg Eivind

    2011-05-01

    Full Text Available Abstract Background Genetically, SNP that are in complete linkage disequilibrium with the causative SNP cannot be distinguished from the causative SNP. The Complete Linkage Disequilibrium (CLD test presented here tests whether a SNP is in complete LD with the causative mutation or not. The performance of the CLD test is evaluated in 1000 simulated datasets. Methods The CLD test consists of two steps i.e. analysis I and analysis II. Analysis I consists of an association analysis of the investigated region. The log-likelihood values from analysis I are next ranked in descending order and in analysis II the CLD test evaluates differences in log-likelihood ratios between the best and second best markers. Under the null-hypothesis distribution, the best SNP is in greater LD with the QTL than the second best, while under the alternative-CLD-hypothesis, the best SNP is alike-in-state with the QTL. To find a significance threshold, the test was also performed on data excluding the causative SNP. The 5th, 10th and 50th highest TCLD value from 1000 replicated analyses were used to control the type-I-error rate of the test at p = 0.005, p = 0.01 and p = 0.05, respectively. Results In a situation where the QTL explained 48% of the phenotypic variance analysis I detected a QTL in 994 replicates (p = 0.001, where 972 were positioned in the correct QTL position. When the causative SNP was excluded from the analysis, 714 replicates detected evidence of a QTL (p = 0.001. In analysis II, the CLD test confirmed 280 causative SNP from 1000 simulations (p = 0.05, i.e. power was 28%. When the effect of the QTL was reduced by doubling the error variance, the power of the test reduced relatively little to 23%. When sequence data were used, the power of the test reduced to 16%. All SNP that were confirmed by the CLD test were positioned in the correct QTL position. Conclusions The CLD test can provide evidence for a causative SNP, but its power may be low in situations

  20. Sample Size and Statistical Conclusions from Tests of Fit to the Rasch Model According to the Rasch Unidimensional Measurement Model (Rumm) Program in Health Outcome Measurement.

    Science.gov (United States)

    Hagell, Peter; Westergren, Albert

    Sample size is a major factor in statistical null hypothesis testing, which is the basis for many approaches to testing Rasch model fit. Few sample size recommendations for testing fit to the Rasch model concern the Rasch Unidimensional Measurement Models (RUMM) software, which features chi-square and ANOVA/F-ratio based fit statistics, including Bonferroni and algebraic sample size adjustments. This paper explores the occurrence of Type I errors with RUMM fit statistics, and the effects of algebraic sample size adjustments. Data with simulated Rasch model fitting 25-item dichotomous scales and sample sizes ranging from N = 50 to N = 2500 were analysed with and without algebraically adjusted sample sizes. Results suggest the occurrence of Type I errors with N less then or equal to 500, and that Bonferroni correction as well as downward algebraic sample size adjustment are useful to avoid such errors, whereas upward adjustment of smaller samples falsely signal misfit. Our observations suggest that sample sizes around N = 250 to N = 500 may provide a good balance for the statistical interpretation of the RUMM fit statistics studied here with respect to Type I errors and under the assumption of Rasch model fit within the examined frame of reference (i.e., about 25 item parameters well targeted to the sample).

  1. Statistical inference for the additive hazards model under outcome-dependent sampling.

    Science.gov (United States)

    Yu, Jichang; Liu, Yanyan; Sandler, Dale P; Zhou, Haibo

    2015-09-01

    Cost-effective study design and proper inference procedures for data from such designs are always of particular interests to study investigators. In this article, we propose a biased sampling scheme, an outcome-dependent sampling (ODS) design for survival data with right censoring under the additive hazards model. We develop a weighted pseudo-score estimator for the regression parameters for the proposed design and derive the asymptotic properties of the proposed estimator. We also provide some suggestions for using the proposed method by evaluating the relative efficiency of the proposed method against simple random sampling design and derive the optimal allocation of the subsamples for the proposed design. Simulation studies show that the proposed ODS design is more powerful than other existing designs and the proposed estimator is more efficient than other estimators. We apply our method to analyze a cancer study conducted at NIEHS, the Cancer Incidence and Mortality of Uranium Miners Study, to study the risk of radon exposure to cancer.

  2. Statistical aspects of evolution under natural selection, with implications for the advantage of sexual reproduction.

    Science.gov (United States)

    Crouch, Daniel J M

    2017-10-27

    The prevalence of sexual reproduction remains mysterious, as it poses clear evolutionary drawbacks compared to reproducing asexually. Several possible explanations exist, with one of the most likely being that finite population size causes linkage disequilibria to randomly generate and impede the progress of natural selection, and that these are eroded by recombination via sexual reproduction. Previous investigations have either analysed this phenomenon in detail for small numbers of loci, or performed population simulations for many loci. Here we present a quantitative genetic model for fitness, based on the Price Equation, in order to examine the theoretical consequences of randomly generated linkage disequilibria when there are many loci. In addition, most previous work has been concerned with the long-term consequences of deleterious linkage disequilibria for population fitness. The expected change in mean fitness between consecutive generations, a measure of short-term evolutionary success, is shown under random environmental influences to be related to the autocovariance in mean fitness between the generations, capturing the effects of stochastic forces such as genetic drift. Interaction between genetic drift and natural selection, due to randomly generated linkage disequilibria, is demonstrated to be one possible source of mean fitness autocovariance. This suggests a possible role for sexual reproduction in reducing the negative effects of genetic drift, thereby improving the short-term efficacy of natural selection. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. The use of statistical tools in field testing of putative effects of genetically modified plants on nontarget organisms.

    Science.gov (United States)

    Semenov, Alexander V; Elsas, Jan Dirk; Glandorf, Debora C M; Schilthuizen, Menno; Boer, Willem F

    2013-08-01

    To fulfill existing guidelines, applicants that aim to place their genetically modified (GM) insect-resistant crop plants on the market are required to provide data from field experiments that address the potential impacts of the GM plants on nontarget organisms (NTO's). Such data may be based on varied experimental designs. The recent EFSA guidance document for environmental risk assessment (2010) does not provide clear and structured suggestions that address the statistics of field trials on effects on NTO's. This review examines existing practices in GM plant field testing such as the way of randomization, replication, and pseudoreplication. Emphasis is placed on the importance of design features used for the field trials in which effects on NTO's are assessed. The importance of statistical power and the positive and negative aspects of various statistical models are discussed. Equivalence and difference testing are compared, and the importance of checking the distribution of experimental data is stressed to decide on the selection of the proper statistical model. While for continuous data (e.g., pH and temperature) classical statistical approaches - for example, analysis of variance (ANOVA) - are appropriate, for discontinuous data (counts) only generalized linear models (GLM) are shown to be efficient. There is no golden rule as to which statistical test is the most appropriate for any experimental situation. In particular, in experiments in which block designs are used and covariates play a role GLMs should be used. Generic advice is offered that will help in both the setting up of field testing and the interpretation and data analysis of the data obtained in this testing. The combination of decision trees and a checklist for field trials, which are provided, will help in the interpretation of the statistical analyses of field trials and to assess whether such analyses were correctly applied. We offer generic advice to risk assessors and applicants that will

  4. IMPLEMENTATION AND VALIDATION OF STATISTICAL TESTS IN RESEARCH'S SOFTWARE HELPING DATA COLLECTION AND PROTOCOLS ANALYSIS IN SURGERY.

    Science.gov (United States)

    Kuretzki, Carlos Henrique; Campos, Antônio Carlos Ligocki; Malafaia, Osvaldo; Soares, Sandramara Scandelari Kusano de Paula; Tenório, Sérgio Bernardo; Timi, Jorge Rufino Ribas

    2016-03-01

    The use of information technology is often applied in healthcare. With regard to scientific research, the SINPE(c) - Integrated Electronic Protocols was created as a tool to support researchers, offering clinical data standardization. By the time, SINPE(c) lacked statistical tests obtained by automatic analysis. Add to SINPE(c) features for automatic realization of the main statistical methods used in medicine . The study was divided into four topics: check the interest of users towards the implementation of the tests; search the frequency of their use in health care; carry out the implementation; and validate the results with researchers and their protocols. It was applied in a group of users of this software in their thesis in the strict sensu master and doctorate degrees in one postgraduate program in surgery. To assess the reliability of the statistics was compared the data obtained both automatically by SINPE(c) as manually held by a professional in statistics with experience with this type of study. There was concern for the use of automatic statistical tests, with good acceptance. The chi-square, Mann-Whitney, Fisher and t-Student were considered as tests frequently used by participants in medical studies. These methods have been implemented and thereafter approved as expected. The incorporation of the automatic SINPE (c) Statistical Analysis was shown to be reliable and equal to the manually done, validating its use as a research tool for medical research.

  5. Strategies for Testing Statistical and Practical Significance in Detecting DIF with Logistic Regression Models

    Science.gov (United States)

    Fidalgo, Angel M.; Alavi, Seyed Mohammad; Amirian, Seyed Mohammad Reza

    2014-01-01

    This study examines three controversial aspects in differential item functioning (DIF) detection by logistic regression (LR) models: first, the relative effectiveness of different analytical strategies for detecting DIF; second, the suitability of the Wald statistic for determining the statistical significance of the parameters of interest; and…

  6. The Effects of Pre-Lecture Quizzes on Test Anxiety and Performance in a Statistics Course

    Science.gov (United States)

    Brown, Michael J.; Tallon, Jennifer

    2015-01-01

    The purpose of our study was to examine the effects of pre-lecture quizzes in a statistics course. Students (N = 70) from 2 sections of an introductory statistics course served as participants in this study. One section completed pre-lecture quizzes whereas the other section did not. Completing pre-lecture quizzes was associated with improved exam…

  7. EPS-LASSO: Test for High-Dimensional Regression Under Extreme Phenotype Sampling of Continuous Traits.

    Science.gov (United States)

    Xu, Chao; Fang, Jian; Shen, Hui; Wang, Yu-Ping; Deng, Hong-Wen

    2018-01-25

    Extreme phenotype sampling (EPS) is a broadly-used design to identify candidate genetic factors contributing to the variation of quantitative traits. By enriching the signals in extreme phenotypic samples, EPS can boost the association power compared to random sampling. Most existing statistical methods for EPS examine the genetic factors individually, despite many quantitative traits have multiple genetic factors underlying their variation. It is desirable to model the joint effects of genetic factors, which may increase the power and identify novel quantitative trait loci under EPS. The joint analysis of genetic data in high-dimensional situations requires specialized techniques, e.g., the least absolute shrinkage and selection operator (LASSO). Although there are extensive research and application related to LASSO, the statistical inference and testing for the sparse model under EPS remain unknown. We propose a novel sparse model (EPS-LASSO) with hypothesis test for high-dimensional regression under EPS based on a decorrelated score function. The comprehensive simulation shows EPS-LASSO outperforms existing methods with stable type I error and FDR control. EPS-LASSO can provide a consistent power for both low- and high-dimensional situations compared with the other methods dealing with high-dimensional situations. The power of EPS-LASSO is close to other low-dimensional methods when the causal effect sizes are small and is superior when the effects are large. Applying EPS-LASSO to a transcriptome-wide gene expression study for obesity reveals 10 significant body mass index associated genes. Our results indicate that EPS-LASSO is an effective method for EPS data analysis, which can account for correlated predictors. The source code is available at https://github.com/xu1912/EPSLASSO. hdeng2@tulane.edu. Supplementary data are available at Bioinformatics online. © The Author (2018). Published by Oxford University Press. All rights reserved. For Permissions, please

  8. A simple and robust statistical framework for planning, analysing and interpreting faecal egg count reduction test (FECRT) studies

    DEFF Research Database (Denmark)

    Denwood, M.J.; McKendrick, I.J.; Matthews, L.

    Introduction. There is an urgent need for a method of analysing FECRT data that is computationally simple and statistically robust. A method for evaluating the statistical power of a proposed FECRT study would also greatly enhance the current guidelines. Methods. A novel statistical framework has...... been developed that evaluates observed FECRT data against two null hypotheses: (1) the observed efficacy is consistent with the expected efficacy, and (2) the observed efficacy is inferior to the expected efficacy. The method requires only four simple summary statistics of the observed data. Power...... that the notional type 1 error rate of the new statistical test is accurate. Power calculations demonstrate a power of only 65% with a sample size of 20 treatment and control animals, which increases to 69% with 40 control animals or 79% with 40 treatment animals. Discussion. The method proposed is simple...

  9. Performance of Modified Test Statistics in Covariance and Correlation Structure Analysis under Conditions of Multivariate Nonnormality.

    Science.gov (United States)

    Fouladi, Rachel T.

    2000-01-01

    Provides an overview of standard and modified normal theory and asymptotically distribution-free covariance and correlation structure analysis techniques and details Monte Carlo simulation results on Type I and Type II error control. Demonstrates through the simulation that robustness and nonrobustness of structure analysis techniques vary as a…

  10. Spiked proteomic standard dataset for testing label-free quantitative software and statistical methods

    Directory of Open Access Journals (Sweden)

    Claire Ramus

    2016-03-01

    Full Text Available This data article describes a controlled, spiked proteomic dataset for which the “ground truth” of variant proteins is known. It is based on the LC-MS analysis of samples composed of a fixed background of yeast lysate and different spiked amounts of the UPS1 mixture of 48 recombinant proteins. It can be used to objectively evaluate bioinformatic pipelines for label-free quantitative analysis, and their ability to detect variant proteins with good sensitivity and low false discovery rate in large-scale proteomic studies. More specifically, it can be useful for tuning software tools parameters, but also testing new algorithms for label-free quantitative analysis, or for evaluation of downstream statistical methods. The raw MS files can be downloaded from ProteomeXchange with identifier http://www.ebi.ac.uk/pride/archive/projects/PXD001819. Starting from some raw files of this dataset, we also provide here some processed data obtained through various bioinformatics tools (including MaxQuant, Skyline, MFPaQ, IRMa-hEIDI and Scaffold in different workflows, to exemplify the use of such data in the context of software benchmarking, as discussed in details in the accompanying manuscript [1]. The experimental design used here for data processing takes advantage of the different spike levels introduced in the samples composing the dataset, and processed data are merged in a single file to facilitate the evaluation and illustration of software tools results for the detection of variant proteins with different absolute expression levels and fold change values.

  11. Proficiency Testing for Determination of Water Content in Toluene of Chemical Reagents by iteration robust statistic technique

    Science.gov (United States)

    Wang, Hao; Wang, Qunwei; He, Ming

    2018-05-01

    In order to investigate and improve the level of detection technology of water content in liquid chemical reagents of domestic laboratories, proficiency testing provider PT0031 (CNAS) has organized proficiency testing program of water content in toluene, 48 laboratories from 18 provinces/cities/municipals took part in the PT. This paper introduces the implementation process of proficiency testing for determination of water content in toluene, including sample preparation, homogeneity and stability test, the results of statistics of iteration robust statistic technique and analysis, summarized and analyzed those of the different test standards which are widely used in the laboratories, put forward the technological suggestions for the improvement of the test quality of water content. Satisfactory results were obtained by 43 laboratories, amounting to 89.6% of the total participating laboratories.

  12. Characterization of Sensory-Motor Behavior Under Cognitive Load Using a New Statistical Platform for Studies of Embodied Cognition

    Directory of Open Access Journals (Sweden)

    Jihye Ryu

    2018-04-01

    Full Text Available The field of enacted/embodied cognition has emerged as a contemporary attempt to connect the mind and body in the study of cognition. However, there has been a paucity of methods that enable a multi-layered approach tapping into different levels of functionality within the nervous systems (e.g., continuously capturing in tandem multi-modal biophysical signals in naturalistic settings. The present study introduces a new theoretical and statistical framework to characterize the influences of cognitive demands on biophysical rhythmic signals harnessed from deliberate, spontaneous and autonomic activities. In this study, nine participants performed a basic pointing task to communicate a decision while they were exposed to different levels of cognitive load. Within these decision-making contexts, we examined the moment-by-moment fluctuations in the peak amplitude and timing of the biophysical time series data (e.g., continuous waveforms extracted from hand kinematics and heart signals. These spike-trains data offered high statistical power for personalized empirical statistical estimation and were well-characterized by a Gamma process. Our approach enabled the identification of different empirically estimated families of probability distributions to facilitate inference regarding the continuous physiological phenomena underlying cognitively driven decision-making. We found that the same pointing task revealed shifts in the probability distribution functions (PDFs of the hand kinematic signals under study and were accompanied by shifts in the signatures of the heart inter-beat-interval timings. Within the time scale of an experimental session, marked changes in skewness and dispersion of the distributions were tracked on the Gamma parameter plane with 95% confidence. The results suggest that traditional theoretical assumptions of stationarity and normality in biophysical data from the nervous systems are incongruent with the true statistical nature of

  13. Characterization of Sensory-Motor Behavior Under Cognitive Load Using a New Statistical Platform for Studies of Embodied Cognition

    Science.gov (United States)

    Ryu, Jihye; Torres, Elizabeth B.

    2018-01-01

    The field of enacted/embodied cognition has emerged as a contemporary attempt to connect the mind and body in the study of cognition. However, there has been a paucity of methods that enable a multi-layered approach tapping into different levels of functionality within the nervous systems (e.g., continuously capturing in tandem multi-modal biophysical signals in naturalistic settings). The present study introduces a new theoretical and statistical framework to characterize the influences of cognitive demands on biophysical rhythmic signals harnessed from deliberate, spontaneous and autonomic activities. In this study, nine participants performed a basic pointing task to communicate a decision while they were exposed to different levels of cognitive load. Within these decision-making contexts, we examined the moment-by-moment fluctuations in the peak amplitude and timing of the biophysical time series data (e.g., continuous waveforms extracted from hand kinematics and heart signals). These spike-trains data offered high statistical power for personalized empirical statistical estimation and were well-characterized by a Gamma process. Our approach enabled the identification of different empirically estimated families of probability distributions to facilitate inference regarding the continuous physiological phenomena underlying cognitively driven decision-making. We found that the same pointing task revealed shifts in the probability distribution functions (PDFs) of the hand kinematic signals under study and were accompanied by shifts in the signatures of the heart inter-beat-interval timings. Within the time scale of an experimental session, marked changes in skewness and dispersion of the distributions were tracked on the Gamma parameter plane with 95% confidence. The results suggest that traditional theoretical assumptions of stationarity and normality in biophysical data from the nervous systems are incongruent with the true statistical nature of empirical data

  14. Test the Overall Significance of p-values by Using Joint Tail Probability of Ordered p-values as Test Statistic

    NARCIS (Netherlands)

    Fang, Yongxiang; Wit, Ernst

    2008-01-01

    Fisher’s combined probability test is the most commonly used method to test the overall significance of a set independent p-values. However, it is very obviously that Fisher’s statistic is more sensitive to smaller p-values than to larger p-value and a small p-value may overrule the other p-values

  15. Mathematical statistics

    CERN Document Server

    Pestman, Wiebe R

    2009-01-01

    This textbook provides a broad and solid introduction to mathematical statistics, including the classical subjects hypothesis testing, normal regression analysis, and normal analysis of variance. In addition, non-parametric statistics and vectorial statistics are considered, as well as applications of stochastic analysis in modern statistics, e.g., Kolmogorov-Smirnov testing, smoothing techniques, robustness and density estimation. For students with some elementary mathematical background. With many exercises. Prerequisites from measure theory and linear algebra are presented.

  16. Rényi statistics for testing composite hypotheses in general exponential models

    Czech Academy of Sciences Publication Activity Database

    Morales, D.; Pardo, L.; Pardo, M. C.; Vajda, Igor

    2004-01-01

    Roč. 38, č. 2 (2004), s. 133-147 ISSN 0233-1888 R&D Projects: GA ČR GA201/02/1391 Grant - others:BMF(ES) 2003-00892; BMF(ES) 2003-04820 Institutional research plan: CEZ:AV0Z1075907 Keywords : natural exponential models * Levy processes * generalized Wald statistics Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.323, year: 2004

  17. Comments on statistical issues in numerical modeling for underground nuclear test monitoring

    International Nuclear Information System (INIS)

    Nicholson, W.L.; Anderson, K.K.

    1993-01-01

    The Symposium concluded with prepared summaries by four experts in the involved disciplines. These experts made no mention of statistics and/or the statistical content of issues. The first author contributed an extemporaneous statement at the Symposium because there are important issues associated with conducting and evaluating numerical modeling that are familiar to statisticians and often treated successfully by them. This note expands upon these extemporaneous remarks

  18. The Functional Task Test (FTT): An Interdisciplinary Testing Protocol to Investigate the Factors Underlying Changes in Astronaut Functional Performance

    Science.gov (United States)

    Bloomberg, J. J.; Lawrence, E. L.; Arzeno, N. M.; Buxton, R. E.; Feiveson, A. H.; Kofman, I. S.; Lee, S. M. C.; Mulavara, A. P.; Peters, B. T.; Platts. S. H.; hide

    2011-01-01

    Exposure to space flight causes adaptations in multiple physiological systems including changes in sensorimotor, cardiovascular, and neuromuscular systems. These changes may affect a crewmember s ability to perform critical mission tasks immediately after landing on a planetary surface. The overall goal of this project is to determine the effects of space flight on functional tests that are representative of high priority exploration mission tasks and to identify the key underlying physiological factors that contribute to decrements in performance. To achieve this goal we developed an interdisciplinary testing protocol (Functional Task Test, FTT) that evaluates both astronaut functional performance and related physiological changes. Functional tests include ladder climbing, hatch opening, jump down, manual manipulation of objects and tool use, seat egress and obstacle avoidance, recovery from a fall and object translation tasks. Physiological measures include assessments of postural and gait control, dynamic visual acuity, fine motor control, plasma volume, orthostatic intolerance, upper- and lower-body muscle strength, power, endurance, control, and neuromuscular drive. Crewmembers perform this integrated test protocol before and after short (Shuttle) and long-duration (ISS) space flight. Data are collected on two sessions before flight, on landing day (Shuttle only) and 1, 6 and 30 days after landing. Preliminary results from both Shuttle and ISS crewmembers indicate decrement in performance of the functional tasks after both short and long-duration space flight. On-going data collection continues to improve the statistical power required to map changes in functional task performance to alterations in physiological systems. The information obtained from this study will be used to design and implement countermeasures that specifically target the physiological systems most responsible for the altered functional performance associated with space flight.

  19. A Test of the Fundamental Physics Underlying Exoplanet Climate Models

    Science.gov (United States)

    Beatty, Thomas; Keating, Dylan; Cowan, Nick; Gaudi, Scott; Kataria, Tiffany; Fortney, Jonathan; Stassun, Keivan; Collins, Karen; Deming, Drake; Bell, Taylor; Dang, Lisa; Rogers, Tamara; Colon, Knicole

    2018-05-01

    A fundamental issue in how we understand exoplanet atmospheres is the assumed physical behavior underlying 3D global circulation models (GCMs). Modeling an entire 3D atmosphere is a Herculean task, and so in exoplanet GCMs we generally assume that there are no clouds, no magnetic effects, and chemical equilibrium (e.g., Kataria et al 2016). These simplifying assumptions are computationally necessary, but at the same time their exclusion allows for a large theoretical lee-way when comparing to data. Thus, though significant discrepancies exist between almost all a priori GCM predictions and their corresponding observations, these are assumed to be due to the lack of clouds, or atmospheric drag, or chemical disequilibrium, in the models (e.g., Wong et al. 2016, Stevenson et al. 2017, Lewis et al. 2017, Zhang et al. 2018). Since these effects compete with one another and have large uncertainties, this makes tests of the fundamental physics in GCMs extremely difficult. To rectify this, we propose to use 88.4 hours of Spitzer time to observe 3.6um and 4.5um phase curves of the transiting giant planet KELT-9b. KELT-9b has an observed dayside temperature of 4600K (Gaudi et al. 2017), which means that there will very likely be no clouds on the day- or nightside, and is hot enough that the atmosphere should be close to local chemical equilibrium. Additionally, we plan to leverage KELT-9b's high temperature to make the first measurement of global wind speed on an exoplanet (Bell & Cowan 2018), giving a constraint on atmospheric drag and magnetic effects. Combined, this means KELT-9b is close to a real-world GCM, without most of the effects present on lower temperature planets. Additionally, since KELT-9b orbits an extremely bright host star these will be the highest signal-to-noise ratio phase curves taken with Spitzer by more than a factor of two. This gives us a unique opportunity to make the first precise and direct investigation into the fundamental physics that are the

  20. Value Added Productivity Indicators: A Statistical Comparison of the Pre-Test/Post-Test Model and Gain Model.

    Science.gov (United States)

    Weerasinghe, Dash; Orsak, Timothy; Mendro, Robert

    In an age of student accountability, public school systems must find procedures for identifying effective schools, classrooms, and teachers that help students continue to learn academically. As a result, researchers have been modeling schools and classrooms to calculate productivity indicators that will withstand not only statistical review but…

  1. Exercise testing in Warmblood sport horses under field conditions.

    Science.gov (United States)

    Munsters, Carolien C B M; van Iwaarden, Alexandra; van Weeren, René; Sloet van Oldruitenborgh-Oosterbaan, Marianne M

    2014-10-01

    Regular exercise testing in Warmblood sport horses may, as in racing, potentially help to characterise fitness indices in different disciplines and at various competition levels and assist in understanding when a horse is 'fit to compete'. In this review an overview is given of the current state of the art of exercise testing in the Olympic disciplines of eventing, show jumping and dressage, and areas for further development are defined. In event horses, a simple four-step incremental exercise test measuring heart rate (HR), lactate concentration (LA) and velocity (V) is most often used. In dressage and riding horses, a wide variety of exercise tests have been developed, including incremental exercise tests, indoor riding tests and lunging tests. In show jumping, the use of a five-step incremental exercise test and exercise tests evaluating technical skills and fatigue of the horse has been reported. The velocity at a plasma LA of 4 mmol/L (VLA4) and HR recovery during submaximal exercise intensity have been shown to be the best parameters in event horses for predicting performance and impending injuries. In riding horses, the fitness level of horses is also an important determinant of injuries. Implementation of regular exercise testing and monitoring of training sessions may have important added value in the assessment of performance ability and potential future injuries in Warmblood sport horses. However, there is an urgent need to standardise methodologies and outcome parameters in order to make results comparable. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Frog Statistics

    Science.gov (United States)

    Whole Frog Project and Virtual Frog Dissection Statistics wwwstats output for January 1 through duplicate or extraneous accesses. For example, in these statistics, while a POST requesting an image is as well. Note that this under-represents the bytes requested. Starting date for following statistics

  3. Uncovering the neural mechanisms underlying learning from tests.

    Directory of Open Access Journals (Sweden)

    Xiaonan L Liu

    Full Text Available People learn better when re-study opportunities are replaced with tests. While researchers have begun to speculate on why testing is superior to study, few studies have directly examined the neural underpinnings of this effect. In this fMRI study, participants engaged in a study phase to learn arbitrary word pairs, followed by a cued recall test (recall second half of pair when cued with first word of pair, re-study of each pair, and finally another cycle of cued recall tests. Brain activation patterns during the first test (recall of the studied pairs predicts performance on the second test. Importantly, while subsequent memory analyses of encoding trials also predict later accuracy, the brain regions involved in predicting later memory success are more extensive for activity during retrieval (testing than during encoding (study. Those additional regions that predict subsequent memory based on their activation at test but not at encoding may be key to understanding the basis of the testing effect.

  4. Automated classification of Permanent Scatterers time-series based on statistical characterization tests

    Science.gov (United States)

    Berti, Matteo; Corsini, Alessandro; Franceschini, Silvia; Iannacone, Jean Pascal

    2013-04-01

    The application of space borne synthetic aperture radar interferometry has progressed, over the last two decades, from the pioneer use of single interferograms for analyzing changes on the earth's surface to the development of advanced multi-interferogram techniques to analyze any sort of natural phenomena which involves movements of the ground. The success of multi-interferograms techniques in the analysis of natural hazards such as landslides and subsidence is widely documented in the scientific literature and demonstrated by the consensus among the end-users. Despite the great potential of this technique, radar interpretation of slope movements is generally based on the sole analysis of average displacement velocities, while the information embraced in multi interferogram time series is often overlooked if not completely neglected. The underuse of PS time series is probably due to the detrimental effect of residual atmospheric errors, which make the PS time series characterized by erratic, irregular fluctuations often difficult to interpret, and also to the difficulty of performing a visual, supervised analysis of the time series for a large dataset. In this work is we present a procedure for automatic classification of PS time series based on a series of statistical characterization tests. The procedure allows to classify the time series into six distinctive target trends (0=uncorrelated; 1=linear; 2=quadratic; 3=bilinear; 4=discontinuous without constant velocity; 5=discontinuous with change in velocity) and retrieve for each trend a series of descriptive parameters which can be efficiently used to characterize the temporal changes of ground motion. The classification algorithms were developed and tested using an ENVISAT datasets available in the frame of EPRS-E project (Extraordinary Plan of Environmental Remote Sensing) of the Italian Ministry of Environment (track "Modena", Northern Apennines). This dataset was generated using standard processing, then the

  5. Nuclear multifragmentation, its relation to general physics. A rich test ground of the fundamentals of statistical mechanics

    International Nuclear Information System (INIS)

    Gross, D.H.E.

    2006-01-01

    Heat can flow from cold to hot at any phase separation even in macroscopic systems. Therefore also Lynden-Bell's famous gravo-thermal catastrophe must be reconsidered. In contrast to traditional canonical Boltzmann-Gibbs statistics this is correctly described only by microcanonical statistics. Systems studied in chemical thermodynamics (ChTh) by using canonical statistics consist of several homogeneous macroscopic phases. Evidently, macroscopic statistics as in chemistry cannot and should not be applied to non-extensive or inhomogeneous systems like nuclei or galaxies. Nuclei are small and inhomogeneous. Multifragmented nuclei are even more inhomogeneous and the fragments even smaller. Phase transitions of first order and especially phase separations therefore cannot be described by a (homogeneous) canonical ensemble. Taking this serious, fascinating perspectives open for statistical nuclear fragmentation as test ground for the basic principles of statistical mechanics, especially of phase transitions, without the use of the thermodynamic limit. Moreover, there is also a lot of similarity between the accessible phase space of fragmenting nuclei and inhomogeneous multistellar systems. This underlines the fundamental significance for statistical physics in general. (orig.)

  6. Histoplasmosis Statistics

    Science.gov (United States)

    ... Testing Treatment & Outcomes Health Professionals Statistics More Resources Candidiasis Candida infections of the mouth, throat, and esophagus Vaginal candidiasis Invasive candidiasis Definition Symptoms Risk & Prevention Sources Diagnosis ...

  7. Conceptualizing Teaching to the Test under Standards-Based Reform

    Science.gov (United States)

    Welsh, Megan E.; Eastwood, Melissa; D'Agostino, Jerome V.

    2014-01-01

    Teacher and school accountability systems based on high-stakes tests are ubiquitous throughout the United States and appear to be growing as a catalyst for reform. As a result, educators have increased the proportion of instructional time devoted to test preparation. Although guidelines for what constitutes appropriate and inappropriate test…

  8. Evaluation of fuel rods behavior - under irradiation test

    International Nuclear Information System (INIS)

    Lameiras, F.S.; Terra, J.L.; Pinto, L.C.M.; Dias, M.S.; Pinheiro, R.B.

    1981-04-01

    By the accompanying of the irradiation of instrumented test fuel rods simulating the operational conditions in reactors, plus the results of post - irradiation exams, tests, evaluation and calibration of analitic modelling of such fuel rods is done. (E.G.) [pt

  9. Extending multivariate distance matrix regression with an effect size measure and the asymptotic null distribution of the test statistic.

    Science.gov (United States)

    McArtor, Daniel B; Lubke, Gitta H; Bergeman, C S

    2017-12-01

    Person-centered methods are useful for studying individual differences in terms of (dis)similarities between response profiles on multivariate outcomes. Multivariate distance matrix regression (MDMR) tests the significance of associations of response profile (dis)similarities and a set of predictors using permutation tests. This paper extends MDMR by deriving and empirically validating the asymptotic null distribution of its test statistic, and by proposing an effect size for individual outcome variables, which is shown to recover true associations. These extensions alleviate the computational burden of permutation tests currently used in MDMR and render more informative results, thus making MDMR accessible to new research domains.

  10. Statistical methods for conducting agreement (comparison of clinical tests) and precision (repeatability or reproducibility) studies in optometry and ophthalmology.

    Science.gov (United States)

    McAlinden, Colm; Khadka, Jyoti; Pesudovs, Konrad

    2011-07-01

    The ever-expanding choice of ocular metrology and imaging equipment has driven research into the validity of their measurements. Consequently, studies of the agreement between two instruments or clinical tests have proliferated in the ophthalmic literature. It is important that researchers apply the appropriate statistical tests in agreement studies. Correlation coefficients are hazardous and should be avoided. The 'limits of agreement' method originally proposed by Altman and Bland in 1983 is the statistical procedure of choice. Its step-by-step use and practical considerations in relation to optometry and ophthalmology are detailed in addition to sample size considerations and statistical approaches to precision (repeatability or reproducibility) estimates. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

  11. Assessment of noise in a digital image using the join-count statistic and the Moran test

    International Nuclear Information System (INIS)

    Kehshih Chuang; Huang, H.K.

    1992-01-01

    It is assumed that data bits of a pixel in digital images can be divided into signal and noise bits. The signal bits occupy the most significant part of the pixel. The signal parts of each pixel are correlated while the noise parts are uncorrelated. Two statistical methods, the Moran test and the join-count statistic, are used to examine the noise parts. Images from computerized tomography, magnetic resonance and computed radiography are used for the evaluation of the noise bits. A residual image is formed by subtracting the original image from its smoothed version. The noise level in the residual image is then identical to that in the original image. Both statistical tests are then performed on the bit planes of the residual image. Results show that most digital images contain only 8-9 bits of correlated information. Both methods are easy to implement and fast to perform. (author)

  12. Prediction of failure enthalpy and reliability of irradiated fuel rod under reactivity-initiated accidents by means of statistical approach

    International Nuclear Information System (INIS)

    Nam, Cheol; Choi, Byeong Kwon; Jeong, Yong Hwan; Jung, Youn Ho

    2001-01-01

    During the last decade, the failure behavior of high-burnup fuel rods under RIA has been an extensive concern since observations of fuel rod failures at low enthalpy. Of great importance is placed on failure prediction of fuel rod in the point of licensing criteria and safety in extending burnup achievement. To address the issue, a statistics-based methodology is introduced to predict failure probability of irradiated fuel rods. Based on RIA simulation results in literature, a failure enthalpy correlation for irradiated fuel rod is constructed as a function of oxide thickness, fuel burnup, and pulse width. From the failure enthalpy correlation, a single damage parameter, equivalent enthalpy, is defined to reflect the effects of the three primary factors as well as peak fuel enthalpy. Moreover, the failure distribution function with equivalent enthalpy is derived, applying a two-parameter Weibull statistical model. Using these equations, the sensitivity analysis is carried out to estimate the effects of burnup, corrosion, peak fuel enthalpy, pulse width and cladding materials used

  13. Comparison of safflower oil extraction kinetics under two characteristic moisture conditions: statistical analysis of non-linear model parameters

    Directory of Open Access Journals (Sweden)

    E. Baümler

    2014-06-01

    Full Text Available In this study the kinetics of oil extraction from partially dehulled safflower seeds under two moisture conditions (7 and 9% dry basis was investigated. The extraction assays were performed using a stirred batch system, thermostated at 50 ºC, using n-hexane as solvent. The data obtained were fitted to a modified diffusion model in order to represent the extraction kinetics. The model took into account a washing and a diffusive step. Fitting parameters were compared statistically for both moisture conditions. The oil yield increased with the extraction time in both cases, although the oil was released at different rates. A comparison of the parameters showed that both the portion extracted in the washing phase and the effective diffusion coefficient were moisture-dependent. The effective diffusivities were 2.81 10-12 and 8.06 10-13 m²s-1 for moisture contents of 7% and 9%, respectively.

  14. Residuals and the Residual-Based Statistic for Testing Goodness of Fit of Structural Equation Models

    Science.gov (United States)

    Foldnes, Njal; Foss, Tron; Olsson, Ulf Henning

    2012-01-01

    The residuals obtained from fitting a structural equation model are crucial ingredients in obtaining chi-square goodness-of-fit statistics for the model. The authors present a didactic discussion of the residuals, obtaining a geometrical interpretation by recognizing the residuals as the result of oblique projections. This sheds light on the…

  15. Basic Mathematics Test Predicts Statistics Achievement and Overall First Year Academic Success

    Science.gov (United States)

    Fonteyne, Lot; De Fruyt, Filip; Dewulf, Nele; Duyck, Wouter; Erauw, Kris; Goeminne, Katy; Lammertyn, Jan; Marchant, Thierry; Moerkerke, Beatrijs; Oosterlinck, Tom; Rosseel, Yves

    2015-01-01

    In the psychology and educational science programs at Ghent University, only 36.1% of the new incoming students in 2011 and 2012 passed all exams. Despite availability of information, many students underestimate the scientific character of social science programs. Statistics courses are a major obstacle in this matter. Not all enrolling students…

  16. Statistical methods in epidemiology. VII. An overview of the chi2 test for 2 x 2 contingency table analysis.

    Science.gov (United States)

    Rigby, A S

    2001-11-10

    The odds ratio is an appropriate method of analysis for data in 2 x 2 contingency tables. However, other methods of analysis exist. One such method is based on the chi2 test of goodness-of-fit. Key players in the development of statistical theory include Pearson, Fisher and Yates. Data are presented in the form of 2 x 2 contingency tables and a method of analysis based on the chi2 test is introduced. There are many variations of the basic test statistic, one of which is the chi2 test with Yates' continuity correction. The usefulness (or not) of Yates' continuity correction is discussed. Problems of interpretation when the method is applied to k x m tables are highlighted. Some properties of the chi2 the test are illustrated by taking examples from the author's teaching experiences. Journal editors should be encouraged to give both observed and expected cell frequencies so that better information comes out of the chi2 test statistic.

  17. Ultrasonic testing of fatigue cracks under various conditions

    International Nuclear Information System (INIS)

    Jessop, T.J.; Cameron, A.G.B.

    1983-01-01

    Reliable detection of the fatigue cracks was possible under all conditions studied. Applied load affected the ultrasonic response in a variety of ways but never more than by 20dB and generally considerably less. Material variations affected the response under applied load by up to 20dB. Oxide in the crack and crack morphology affected the response by up to 9dB (12dB under load). Crack size variations and presence of water had little effect. Sizing accuracy was generally within 2mm although there was a tendency to undersize. The time of flight sizing technique gave the best accuracy if a tensile load was applied

  18. Bending Under Tension Test with Direct Friction Measurement

    DEFF Research Database (Denmark)

    Andreasen, Jan Lasson; Olsson, David Dam; Chodnikiewicz, K.

    2006-01-01

    A special Bending-Under-Tension (BUT) transducer has been developed in which friction around the tool radius can be directly measured when drawing a plane sheet strip around a cylindrical tool-pin under constant back tension. The front tension, back tension and torque on the tool-pin are all...... measured directly, thus enabling accurate measurement of friction and direct determination of lubricant film breakdown for varying normal pressure, sliding speed, tool radius and tool preheat temperature. The transducer is applied in an experimental investigation focusing on limits of lubrication...

  19. Statistical properties of country risk ratings under oil price volatility: Evidence from selected oil-exporting countries

    International Nuclear Information System (INIS)

    Liu, Chang; Sun, Xiaolei; Chen, Jianming; Li, Jianping

    2016-01-01

    This paper focuses on the application of panel models for identification and analysis of influence of oil price volatility on statistical properties of country risk ratings which stem from uncertainty of macroeconomic fluctuations. Firstly, two statistical properties of country risk ratings, volatility clustering and asymmetrical revision were identified in a theoretical framework based on Cruces (2006). Secondly, considering the oil price volatility, numerical experiments were conducted based on extended models to test and verify specific properties of country risk ratings in selected oil-exporting countries. Empirical results suggest that properties of country risk remain comparatively steady despite oil price volatility. It is also found that the oil price volatility can obviously exaggerate the country risk volatility, as it happened during 2007–2009. Country clustering based on the properties of country risk ratings shows that the selected countries maintain a significant clustering tendency. These features are of great importance for estimating risk exposure of international trade and investments in oil export during extreme situations. - Highlights: •Relationship between oil price volatility and country risk is the focus. •An extended model based on Cruces (2006) is proposed. •Volatility clustering and asymmetrical revision of country risk ratings is explored. •Oil price volatility can obviously exaggerate properties of country risk volatility.

  20. Statistical Tests Black swans or dragon-kings? A simple test for deviations from the power law★

    Science.gov (United States)

    Janczura, J.; Weron, R.

    2012-05-01

    We develop a simple test for deviations from power law tails. Actually, from the tails of any distribution. We use this test - which is based on the asymptotic properties of the empirical distribution function - to answer the question whether great natural disasters, financial crashes or electricity price spikes should be classified as dragon-kings or `only' as black swans.

  1. Dynamic behavior of porous concretes under drop weight impact testing

    NARCIS (Netherlands)

    Agar Ozbek, A.S.; Weerheijm, J.; Schlangen, E.; Breugel, K. van

    2013-01-01

    Porous concrete is used as a construction material in various applications mainly as a permeable cementitious material. However, its response under impact loading is generally not considered. Due to the high percentage of its intentional meso-size air pores, porous concrete has a moderate static

  2. Eye Movement Analysis of Information Processing under Different Testing Conditions.

    Science.gov (United States)

    Dillon, Ronna F.

    1985-01-01

    Undergraduates were given complex figural analogies items, and eye movements were observed under three types of feedback: (1) elaborate feedback; (2) subjects verbalized their thinking and application of rules; and (3) no feedback. Both feedback conditions enhanced the rule-governed information processing during inductive reasoning. (Author/GDC)

  3. Elastic response of thermal spray deposits under indentation tests

    International Nuclear Information System (INIS)

    Leigh, S.H.; Lin, C.K.; Berndt, C.C.

    1997-01-01

    The elastic response behavior of thermal spray deposits at Knoop indentations has been investigated using indentation techniques. The ration of hardness to elastic modulus, which is an important prerequisite for the evaluation of indentation fracture toughness, is determined by measuring the elastic recovery of the in-surface dimensions of Knoop indentations. The elastic moduli of thermal spray deposits are in the range of 12%--78% of the comparable bulk materials and reveal the anisotropic behavior of thermal spray deposits. A variety of thermal spray deposits has been examined, including Al 2 O 3 , yttria-stabilized ZrO 2 (YSZ), and NiAl. Statistical tools have been used to evaluate the error estimates of the data

  4. Evaluation of PDA Technical Report No 33. Statistical Testing Recommendations for a Rapid Microbiological Method Case Study.

    Science.gov (United States)

    Murphy, Thomas; Schwedock, Julie; Nguyen, Kham; Mills, Anna; Jones, David

    2015-01-01

    New recommendations for the validation of rapid microbiological methods have been included in the revised Technical Report 33 release from the PDA. The changes include a more comprehensive review of the statistical methods to be used to analyze data obtained during validation. This case study applies those statistical methods to accuracy, precision, ruggedness, and equivalence data obtained using a rapid microbiological methods system being evaluated for water bioburden testing. Results presented demonstrate that the statistical methods described in the PDA Technical Report 33 chapter can all be successfully applied to the rapid microbiological method data sets and gave the same interpretation for equivalence to the standard method. The rapid microbiological method was in general able to pass the requirements of PDA Technical Report 33, though the study shows that there can be occasional outlying results and that caution should be used when applying statistical methods to low average colony-forming unit values. Prior to use in a quality-controlled environment, any new method or technology has to be shown to work as designed by the manufacturer for the purpose required. For new rapid microbiological methods that detect and enumerate contaminating microorganisms, additional recommendations have been provided in the revised PDA Technical Report No. 33. The changes include a more comprehensive review of the statistical methods to be used to analyze data obtained during validation. This paper applies those statistical methods to analyze accuracy, precision, ruggedness, and equivalence data obtained using a rapid microbiological method system being validated for water bioburden testing. The case study demonstrates that the statistical methods described in the PDA Technical Report No. 33 chapter can be successfully applied to rapid microbiological method data sets and give the same comparability results for similarity or difference as the standard method. © PDA, Inc

  5. Test the Overall Significance of p-values by Using Joint Tail Probability of Ordered p-values as Test Statistic

    OpenAIRE

    Fang, Yongxiang; Wit, Ernst

    2008-01-01

    Fisher’s combined probability test is the most commonly used method to test the overall significance of a set independent p-values. However, it is very obviously that Fisher’s statistic is more sensitive to smaller p-values than to larger p-value and a small p-value may overrule the other p-values and decide the test result. This is, in some cases, viewed as a flaw. In order to overcome this flaw and improve the power of the test, the joint tail probability of a set p-values is proposed as a ...

  6. Integrated testing strategy (ITS) for bioaccumulation assessment under REACH

    DEFF Research Database (Denmark)

    Lombardo, Anna; Roncaglioni, Alessandra; Benfentati, Emilio

    2014-01-01

    in a dossier. REACH promotes the use of alternative methods to replace, refine and reduce the use of animal (eco)toxicity testing. Within the EU OSIRIS project, integrated testing strategies (ITSs) have been developed for the rational use of non-animal testing approaches in chemical hazard assessment. Here we......REACH (registration, evaluation, authorisation and restriction of chemicals) regulation requires that all the chemicals produced or imported in Europe above 1 tonne/year are registered. To register a chemical, physicochemical, toxicological and ecotoxicological information needs to be reported...... present an ITS for evaluating the bioaccumulation potential of organic chemicals. The scheme includes the use of all available data (also the non-optimal ones), waiving schemes, analysis of physicochemical properties related to the end point and alternative methods (both in silico and in vitro). In vivo...

  7. Comparison of statistical tests for association between rare variants and binary traits.

    OpenAIRE

    Bacanu, SA; Nelson, MR; Whittaker, JC

    2012-01-01

    : Genome-wide association studies have found thousands of common genetic variants associated with a wide variety of diseases and other complex traits. However, a large portion of the predicted genetic contribution to many traits remains unknown. One plausible explanation is that some of the missing variation is due to the effects of rare variants. Nonetheless, the statistical analysis of rare variants is challenging. A commonly used method is to contrast, within the same region (gene), the fr...

  8. The Bayesian New Statistics: Hypothesis testing, estimation, meta-analysis, and power analysis from a Bayesian perspective.

    Science.gov (United States)

    Kruschke, John K; Liddell, Torrin M

    2018-02-01

    In the practice of data analysis, there is a conceptual distinction between hypothesis testing, on the one hand, and estimation with quantified uncertainty on the other. Among frequentists in psychology, a shift of emphasis from hypothesis testing to estimation has been dubbed "the New Statistics" (Cumming 2014). A second conceptual distinction is between frequentist methods and Bayesian methods. Our main goal in this article is to explain how Bayesian methods achieve the goals of the New Statistics better than frequentist methods. The article reviews frequentist and Bayesian approaches to hypothesis testing and to estimation with confidence or credible intervals. The article also describes Bayesian approaches to meta-analysis, randomized controlled trials, and power analysis.

  9. Freedom of expression in Azerbaijan under test : challenges and prospects

    OpenAIRE

    Madatli, Leyla

    2010-01-01

    This article discusses the ground-breaking judgment in Fatullayev v Azerbaijan in which the European Court ordered the immediate release of imprisoned journalist Eynulla Fatullayev, but who at the time of going to press nevertheless remained in custody. Fatullayev was the founder and chief editor of two newspapers in Azerbaijan well known for their harsh criticism of the Azerbaijani Government. This judgment is of great importance for Azerbaijan as it addresses topical issues under Art.10 ECH...

  10. Bank stress testing under different balance sheet assumptions

    OpenAIRE

    Busch, Ramona; Drescher, Christian; Memmel, Christoph

    2017-01-01

    Using unique supervisory survey data on the impact of a hypothetical interest rate shock on German banks, we analyse price and quantity effects on banks' net interest margin components under different balance sheet assumptions. In the first year, the cross-sectional variation of banks' simulated price effect is nearly eight times as large as the one of the simulated quantity effect. After five years, however, the importance of both effects converges. Large banks adjust their balance sheets mo...

  11. Psychological Processes Underlying Cultivation Effects: Further Tests of Construct Accessibility.

    Science.gov (United States)

    Shrum, L. J.

    1996-01-01

    Describes a study that tested whether the accessibility of information in memory mediates the cultivation effect (the effect of television viewing on social perceptions), consistent with the availability heuristic. Shows that heavy viewers gave higher frequency estimates (cultivation effect) and responded faster (accessibility effect) than did…

  12. Exercise testing in Warmblood sport horses under field conditions

    NARCIS (Netherlands)

    Munsters, Carolien C B M; van Iwaarden, Alexandra; van Weeren, René; Sloet van Oldruitenborgh-Oosterbaan, Marianne M

    2014-01-01

    Regular exercise testing in Warmblood sport horses may, as in racing, potentially help to characterise fitness indices in different disciplines and at various competition levels and assist in understanding when a horse is 'fit to compete'. In this review an overview is given of the current state of

  13. Tensile testing grips are easily assembled under liquid nitrogen

    Science.gov (United States)

    Skalka, R. J.; Vandergrift, E. F.

    1967-01-01

    Split-screw grips for tensile testing provide uniform loading on the specimen shoulders. Holes in the heads enable the screws and specimen to be threaded as an assembly into a grip body, closely controlled guides and seats afford positive seating, and precision machining of mating surfaces minimizes misalignment effects.

  14. Principles Underlying the Bilingual Aphasia Test (BAT) and Its Uses

    Science.gov (United States)

    Paradis, Michel

    2011-01-01

    The Bilingual Aphasia Test (BAT) is designed to be objective (so it can be administered by a lay native speaker of the language) and equivalent across languages (to allow for a comparison between the languages of a given patient as well as across patients from different institutions). It has been used not only with aphasia but also with any…

  15. Democracies under rising inequality : New tests of the redistributive thesis

    NARCIS (Netherlands)

    van der Linde, D.E.

    2017-01-01

    Recent increases in income inequality have led a number of authors to question the redistributive thesis, which predicts higher levels of income inequality will be met with increased redistribution of income, curbing inequality. This dissertation offers a new test of this theory, and sets out to

  16. [Do we always correctly interpret the results of statistical nonparametric tests].

    Science.gov (United States)

    Moczko, Jerzy A

    2014-01-01

    Mann-Whitney, Wilcoxon, Kruskal-Wallis and Friedman tests create a group of commonly used tests to analyze the results of clinical and laboratory data. These tests are considered to be extremely flexible and their asymptotic relative efficiency exceeds 95 percent. Compared with the corresponding parametric tests they do not require checking the fulfillment of the conditions such as the normality of data distribution, homogeneity of variance, the lack of correlation means and standard deviations, etc. They can be used both in the interval and or-dinal scales. The article presents an example Mann-Whitney test, that does not in any case the choice of these four nonparametric tests treated as a kind of gold standard leads to correct inference.

  17. Statistical Diversions

    Science.gov (United States)

    Petocz, Peter; Sowey, Eric

    2008-01-01

    In this article, the authors focus on hypothesis testing--that peculiarly statistical way of deciding things. Statistical methods for testing hypotheses were developed in the 1920s and 1930s by some of the most famous statisticians, in particular Ronald Fisher, Jerzy Neyman and Egon Pearson, who laid the foundations of almost all modern methods of…

  18. Statistical modeling of road contribution as emission sources to total suspended particles (TSP) under MCF model downtown Medellin - Antioquia - Colombia, 2004

    International Nuclear Information System (INIS)

    Gomez, Miryam; Saldarriaga, Julio; Correa, Mauricio; Posada, Enrique; Castrillon M, Francisco Javier

    2007-01-01

    Sand fields, constructions, carbon boilers, roads, and biologic sources are air-contaminant-constituent factors in down town Valle de Aburra, among others. the distribution of road contribution data to total suspended particles according to the source receptor model MCF, source correlation modeling, is nearly a gamma distribution. Chi-square goodness of fit is used to model statistically. This test for goodness of fit also allows estimating the parameters of the distribution utilizing maximum likelihood method. As convergence criteria, the estimation maximization algorithm is used. The mean of road contribution data to total suspended particles according to the source receptor model MCF, is straightforward and validates the road contribution factor to the atmospheric pollution of the zone under study

  19. Design of durability test protocol for vehicular fuel cell systems operated in power-follow mode based on statistical results of on-road data

    Science.gov (United States)

    Xu, Liangfei; Reimer, Uwe; Li, Jianqiu; Huang, Haiyan; Hu, Zunyan; Jiang, Hongliang; Janßen, Holger; Ouyang, Minggao; Lehnert, Werner

    2018-02-01

    City buses using polymer electrolyte membrane (PEM) fuel cells are considered to be the most likely fuel cell vehicles to be commercialized in China. The technical specifications of the fuel cell systems (FCSs) these buses are equipped with will differ based on the powertrain configurations and vehicle control strategies, but can generally be classified into the power-follow and soft-run modes. Each mode imposes different levels of electrochemical stress on the fuel cells. Evaluating the aging behavior of fuel cell stacks under the conditions encountered in fuel cell buses requires new durability test protocols based on statistical results obtained during actual driving tests. In this study, we propose a systematic design method for fuel cell durability test protocols that correspond to the power-follow mode based on three parameters for different fuel cell load ranges. The powertrain configurations and control strategy are described herein, followed by a presentation of the statistical data for the duty cycles of FCSs in one city bus in the demonstration project. Assessment protocols are presented based on the statistical results using mathematical optimization methods, and are compared to existing protocols with respect to common factors, such as time at open circuit voltage and root-mean-square power.

  20. Design, Analysis and Test of Logic Circuits Under Uncertainty

    CERN Document Server

    Krishnaswamy, Smita; Hayes, John P

    2013-01-01

    Integrated circuits (ICs) increasingly exhibit uncertain characteristics due to soft errors, inherently probabilistic devices, and manufacturing variability. As device technologies scale, these effects can be detrimental to the reliability of logic circuits.  To improve future semiconductor designs, this book describes methods for analyzing, designing, and testing circuits subject to probabilistic effects. The authors first develop techniques to model inherently probabilistic methods in logic circuits and to test circuits for determining their reliability after they are manufactured. Then, they study error-masking mechanisms intrinsic to digital circuits and show how to leverage them to design more reliable circuits.  The book describes techniques for:   • Modeling and reasoning about probabilistic behavior in logic circuits, including a matrix-based reliability-analysis framework;   • Accurate analysis of soft-error rate (SER) based on functional-simulation, sufficiently scalable for use in gate-l...

  1. Mapping cell populations in flow cytometry data for cross‐sample comparison using the Friedman–Rafsky test statistic as a distance measure

    Science.gov (United States)

    Hsiao, Chiaowen; Liu, Mengya; Stanton, Rick; McGee, Monnie; Qian, Yu

    2015-01-01

    Abstract Flow cytometry (FCM) is a fluorescence‐based single‐cell experimental technology that is routinely applied in biomedical research for identifying cellular biomarkers of normal physiological responses and abnormal disease states. While many computational methods have been developed that focus on identifying cell populations in individual FCM samples, very few have addressed how the identified cell populations can be matched across samples for comparative analysis. This article presents FlowMap‐FR, a novel method for cell population mapping across FCM samples. FlowMap‐FR is based on the Friedman–Rafsky nonparametric test statistic (FR statistic), which quantifies the equivalence of multivariate distributions. As applied to FCM data by FlowMap‐FR, the FR statistic objectively quantifies the similarity between cell populations based on the shapes, sizes, and positions of fluorescence data distributions in the multidimensional feature space. To test and evaluate the performance of FlowMap‐FR, we simulated the kinds of biological and technical sample variations that are commonly observed in FCM data. The results show that FlowMap‐FR is able to effectively identify equivalent cell populations between samples under scenarios of proportion differences and modest position shifts. As a statistical test, FlowMap‐FR can be used to determine whether the expression of a cellular marker is statistically different between two cell populations, suggesting candidates for new cellular phenotypes by providing an objective statistical measure. In addition, FlowMap‐FR can indicate situations in which inappropriate splitting or merging of cell populations has occurred during gating procedures. We compared the FR statistic with the symmetric version of Kullback–Leibler divergence measure used in a previous population matching method with both simulated and real data. The FR statistic outperforms the symmetric version of KL‐distance in distinguishing

  2. Mapping cell populations in flow cytometry data for cross-sample comparison using the Friedman-Rafsky test statistic as a distance measure.

    Science.gov (United States)

    Hsiao, Chiaowen; Liu, Mengya; Stanton, Rick; McGee, Monnie; Qian, Yu; Scheuermann, Richard H

    2016-01-01

    Flow cytometry (FCM) is a fluorescence-based single-cell experimental technology that is routinely applied in biomedical research for identifying cellular biomarkers of normal physiological responses and abnormal disease states. While many computational methods have been developed that focus on identifying cell populations in individual FCM samples, very few have addressed how the identified cell populations can be matched across samples for comparative analysis. This article presents FlowMap-FR, a novel method for cell population mapping across FCM samples. FlowMap-FR is based on the Friedman-Rafsky nonparametric test statistic (FR statistic), which quantifies the equivalence of multivariate distributions. As applied to FCM data by FlowMap-FR, the FR statistic objectively quantifies the similarity between cell populations based on the shapes, sizes, and positions of fluorescence data distributions in the multidimensional feature space. To test and evaluate the performance of FlowMap-FR, we simulated the kinds of biological and technical sample variations that are commonly observed in FCM data. The results show that FlowMap-FR is able to effectively identify equivalent cell populations between samples under scenarios of proportion differences and modest position shifts. As a statistical test, FlowMap-FR can be used to determine whether the expression of a cellular marker is statistically different between two cell populations, suggesting candidates for new cellular phenotypes by providing an objective statistical measure. In addition, FlowMap-FR can indicate situations in which inappropriate splitting or merging of cell populations has occurred during gating procedures. We compared the FR statistic with the symmetric version of Kullback-Leibler divergence measure used in a previous population matching method with both simulated and real data. The FR statistic outperforms the symmetric version of KL-distance in distinguishing equivalent from nonequivalent cell

  3. Statistical Considerations in Choosing a Test Reliability Coefficient. ACT Research Report Series, 2012 (10)

    Science.gov (United States)

    Woodruff, David; Wu, Yi-Fang

    2012-01-01

    The purpose of this paper is to illustrate alpha's robustness and usefulness, using actual and simulated educational test data. The sampling properties of alpha are compared with the sampling properties of several other reliability coefficients: Guttman's lambda[subscript 2], lambda[subscript 4], and lambda[subscript 6]; test-retest reliability;…

  4. A Powerful Test of the Autoregressive Unit Root Hypothesis Based on a Tuning Parameter Free Statistic

    DEFF Research Database (Denmark)

    Nielsen, Morten Ørregaard

    This paper presents a family of simple nonparametric unit root tests indexed by one parameter, d, and containing Breitung's (2002) test as the special case d = 1. It is shown that (i) each member of the family with d > 0 is consistent, (ii) the asymptotic distribution depends on d, and thus refle...

  5. Application of the modified chi-square ratio statistic in a stepwise procedure for cascade impactor equivalence testing.

    Science.gov (United States)

    Weber, Benjamin; Lee, Sau L; Delvadia, Renishkumar; Lionberger, Robert; Li, Bing V; Tsong, Yi; Hochhaus, Guenther

    2015-03-01

    Equivalence testing of aerodynamic particle size distribution (APSD) through multi-stage cascade impactors (CIs) is important for establishing bioequivalence of orally inhaled drug products. Recent work demonstrated that the median of the modified chi-square ratio statistic (MmCSRS) is a promising metric for APSD equivalence testing of test (T) and reference (R) products as it can be applied to a reduced number of CI sites that are more relevant for lung deposition. This metric is also less sensitive to the increased variability often observed for low-deposition sites. A method to establish critical values for the MmCSRS is described here. This method considers the variability of the R product by employing a reference variance scaling approach that allows definition of critical values as a function of the observed variability of the R product. A stepwise CI equivalence test is proposed that integrates the MmCSRS as a method for comparing the relative shapes of CI profiles and incorporates statistical tests for assessing equivalence of single actuation content and impactor sized mass. This stepwise CI equivalence test was applied to 55 published CI profile scenarios, which were classified as equivalent or inequivalent by members of the Product Quality Research Institute working group (PQRI WG). The results of the stepwise CI equivalence test using a 25% difference in MmCSRS as an acceptance criterion provided the best matching with those of the PQRI WG as decisions of both methods agreed in 75% of the 55 CI profile scenarios.

  6. A test for monitoring under- and overtreatment in Dutch hospitals

    OpenAIRE

    Lenz, Oliver Urs; Oberski, Daniel L

    2017-01-01

    Over- and undertreatment harm patients and society and confound other healthcare quality measures. Despite a growing body of research covering specific conditions, we lack tools to systematically detect and measure over- and undertreatment in hospitals. We demonstrate a test used to monitor over- and undertreatment in Dutch hospitals, and illustrate its results applied to the aggregated administrative treatment data of 1,836,349 patients at 89 hospitals in 2013. We employ a random effects mod...

  7. Accelerated Testing with Multiple Failure Modes under Several Temperature Conditions

    OpenAIRE

    Zongyue Yu; Zhiqian Ren; Junyong Tao; Xun Chen

    2014-01-01

    A complicated device may have multiple failure modes, and some of the failure modes are sensitive to low temperatures. To assess the reliability of a product with multiple failure modes, this paper presents an accelerated testing in which both of the high temperatures and the low temperatures are applied. Firstly, an acceleration model based on the Arrhenius model but accounting for the influence of both the high temperatures and low temperatures is proposed. Accordingly, an accelerated testi...

  8. INVITATION TO PERFORM Y2K TESTING UNDER UNIX

    CERN Multimedia

    CERN Y2K Co-ordinator

    1999-01-01

    IntroductionA special AFS cell Ôy2k.cern.chÕ has been established to allow service managers and users to test y2k compliance.In addition to AFS, the cluster consists of machines representing all the Unix flavours in use at CERN (AIX, DUNIX, HP-UX, IRIX, LINUX, and SOLARIS).More information can be obtained from the page: http://wwwinfo.cern.ch/pdp/bis/y2k/y2kplus.htmlTesting scheduleThe cluster will be set to 25 December 1999 on fixed days and then left running for three weeks. This gives people one week to prepare test programs in 1999 and two weeks to check the consequences of passing into year 2000. These fixed dates are set as follows:— 19 May 1999, date set to 25/12/99 (year 2000 starts on 26 May) — 9 June1999, date set to 25/12/99 (year 2000 starts on 16 June)— 30 June 1999, date set to 25/12/99 (year 2000 starts on 7 July)If more than these three sessions are needed an announcement will be made later. RegistrationThe following Web page should be used for r...

  9. Bending Under Tension Test with Direct Friction Measurement

    DEFF Research Database (Denmark)

    Andreasen, Jan Lasson; Olsson, David Dam; Chodnikiewicz, K.

    2004-01-01

    A special BUT-transducer has been developed in which friction around the tool radius can be directly measured when drawing a plane sheet strip around a cylindrical tool-pin under constant back tension. The front tension, back tension and torque on the tool-pin are all measured directly, thus...... enabling accurate measurement of friction and direct determination of lubricant film breakdown for varying normal pressure, sliding speed, tool radius and tool preheat temperature. The transducer is applied in an experimental investigation focusing on limits of lubrication in drawing of stainless steel...

  10. Statistically based reevaluation of PISC-II round robin test data

    International Nuclear Information System (INIS)

    Heasler, P.G.; Taylor, T.T.; Doctor, S.R.

    1993-05-01

    This report presents a re-analysis of an international PISC-II (Programme for Inspection of Steel Components, Phase 2) round-robin inspection results using formal statistical techniques to account for experimental error. The analysis examines US team performance vs. other participants performance,flaw sizing performance and errors associated with flaw sizing, factors influencing flaw detection probability, performance of all participants with respect to recently adopted ASME Section 11 flaw detection performance demonstration requirements, and develops conclusions concerning ultrasonic inspection capability. Inspection data were gathered on four heavy section steel components which included two plates and two nozzle configurations

  11. Statistical homogeneity tests applied to large data sets from high energy physics experiments

    Science.gov (United States)

    Trusina, J.; Franc, J.; Kůs, V.

    2017-12-01

    Homogeneity tests are used in high energy physics for the verification of simulated Monte Carlo samples, it means if they have the same distribution as a measured data from particle detector. Kolmogorov-Smirnov, χ 2, and Anderson-Darling tests are the most used techniques to assess the samples’ homogeneity. Since MC generators produce plenty of entries from different models, each entry has to be re-weighted to obtain the same sample size as the measured data has. One way of the homogeneity testing is through the binning. If we do not want to lose any information, we can apply generalized tests based on weighted empirical distribution functions. In this paper, we propose such generalized weighted homogeneity tests and introduce some of their asymptotic properties. We present the results based on numerical analysis which focuses on estimations of the type-I error and power of the test. Finally, we present application of our homogeneity tests to data from the experiment DØ in Fermilab.

  12. Statistical Analysis of Compressive and Flexural Test Results on the Sustainable Adobe Reinforced with Steel Wire Mesh

    Science.gov (United States)

    Jokhio, Gul A.; Syed Mohsin, Sharifah M.; Gul, Yasmeen

    2018-04-01

    It has been established that Adobe provides, in addition to being sustainable and economic, a better indoor air quality without spending extensive amounts of energy as opposed to the modern synthetic materials. The material, however, suffers from weak structural behaviour when subjected to adverse loading conditions. A wide range of mechanical properties has been reported in literature owing to lack of research and standardization. The present paper presents the statistical analysis of the results that were obtained through compressive and flexural tests on Adobe samples. Adobe specimens with and without wire mesh reinforcement were tested and the results were reported. The statistical analysis of these results presents an interesting read. It has been found that the compressive strength of adobe increases by about 43% after adding a single layer of wire mesh reinforcement. This increase is statistically significant. The flexural response of Adobe has also shown improvement with the addition of wire mesh reinforcement, however, the statistical significance of the same cannot be established.

  13. Nonlinear Parameter Estimation in Microbiological Degradation Systems and Statistic Test for Common Estimation

    DEFF Research Database (Denmark)

    Sommer, Helle Mølgaard; Holst, Helle; Spliid, Henrik

    1995-01-01

    Three identical microbiological experiments were carried out and analysed in order to examine the variability of the parameter estimates. The microbiological system consisted of a substrate (toluene) and a biomass (pure culture) mixed together in an aquifer medium. The degradation of the substrate...... and the growth of the biomass are described by the Monod model consisting of two nonlinear coupled first-order differential equations. The objective of this study was to estimate the kinetic parameters in the Monod model and to test whether the parameters from the three identical experiments have the same values....... Estimation of the parameters was obtained using an iterative maximum likelihood method and the test used was an approximative likelihood ratio test. The test showed that the three sets of parameters were identical only on a 4% alpha level....

  14. Behaviour of Ti-doped CFCs under thermal fatigue tests

    Energy Technology Data Exchange (ETDEWEB)

    Centeno, A. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Pintsuk, G.; Linke, J. [Forschungszentrum Juelich GmbH, EURATOM Association, 52425 Juelich (Germany); Gualco, C. [Ansaldo Energia, I-16152 Genoa (Italy); Blanco, C., E-mail: clara@incar.csic.es [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain); Santamaria, R.; Granda, M.; Menendez, R. [Instituto Nacional del Carbon (CSIC), Apdo. 73, 33080 Oviedo (Spain)

    2011-01-15

    In spite of the remarkable progress in the design of in-vessel components for the divertor of the first International Thermonuclear Experimental Reactor (ITER), a great effort is still put into the development of manufacturing technologies for carbon armour with improved properties. Newly developed 3D titanium-doped carbon fibre reinforced composites and their corresponding undoped counterparts were brazed to a CuCrZr heat sink to produce actively cooled flat tile mock-ups. By exposing the mock-ups to thermal fatigue tests in an electron beam test facility, the material behaviour and the brazing between the individual constituents in the mock-up was qualified. The mock-ups with titanium-doped CFCs exhibited a significantly improved thermal fatigue resistance compared with those undoped materials. The comparison of these mock-ups with those produced using pristine NB31, one of the reference materials as plasma facing material for ITER, showed almost identical results, indicating the high potential of Ti-doped CFCs due to their improved thermal shock resistance.

  15. Testing Paradigms of Ecosystem Change under Climate Warming in Antarctica

    Science.gov (United States)

    Melbourne-Thomas, Jessica; Constable, Andrew; Wotherspoon, Simon; Raymond, Ben

    2013-01-01

    Antarctic marine ecosystems have undergone significant changes as a result of human activities in the past and are now responding in varied and often complicated ways to climate change impacts. Recent years have seen the emergence of large-scale mechanistic explanations–or “paradigms of change”–that attempt to synthesize our understanding of past and current changes. In many cases, these paradigms are based on observations that are spatially and temporally patchy. The West Antarctic Peninsula (WAP), one of Earth’s most rapidly changing regions, has been an area of particular research focus. A recently proposed mechanistic explanation for observed changes in the WAP region relates changes in penguin populations to variability in krill biomass and regional warming. While this scheme is attractive for its simplicity and chronology, it may not account for complex spatio-temporal processes that drive ecosystem dynamics in the region. It might also be difficult to apply to other Antarctic regions that are experiencing some, though not all, of the changes documented for the WAP. We use qualitative network models of differing levels of complexity to test paradigms of change for the WAP ecosystem. Importantly, our approach captures the emergent effects of feedback processes in complex ecological networks and provides a means to identify and incorporate uncertain linkages between network elements. Our findings highlight key areas of uncertainty in the drivers of documented trends, and suggest that a greater level of model complexity is needed in devising explanations for ecosystem change in the Southern Ocean. We suggest that our network approach to evaluating a recent and widely cited paradigm of change for the Antarctic region could be broadly applied in hypothesis testing for other regions and research fields. PMID:23405116

  16. Statistical reliability assessment of UT round-robin test data for piping welds

    International Nuclear Information System (INIS)

    Kim, H.M.; Park, I.K.; Park, U.S.; Park, Y.W.; Kang, S.C.; Lee, J.H.

    2004-01-01

    Ultrasonic NDE is one of important technologies in the life-time maintenance of nuclear power plant. Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of ultrasonic inspection system is affected by its ability. The performance demonstration round robin was conducted to quantify the capability of ultrasonic inspection for in-service. Several teams employed procedures that met or exceeded with ASME sec. XI code requirements detected the piping of nuclear power plant with various cracks to evaluate the capability of detection and sizing. In this paper, the statistical reliability assessment of ultrasonic nondestructive inspection data using probability of detection (POD) is presented. The result of POD using logistic model was useful to the reliability assessment for the NDE hit or miss data. (orig.)

  17. A Statistical Test of Correlations and Periodicities in the Geological Records

    Science.gov (United States)

    Yabushita, S.

    1997-09-01

    Matsumoto & Kubotani argued that there is a positive and statistically significant correlation between cratering and mass extinction. This argument is critically examined by adopting a method of Ertel used by Matsumoto & Kubotani but by applying it more directly to the extinction and cratering records. It is shown that on the null-hypothesis of random distribution of crater ages, the observed correlation has a probability of occurrence of 13%. However, when large craters are excluded whose ages agree with the times of peaks of extinction rate of marine fauna, one obtains a negative correlation. This result strongly indicates that mass extinction are not due to accumulation of impacts but due to isolated gigantic impacts.

  18. Statistical model for the mechanical behavior of the tissue engineering non-woven fibrous matrices under large deformation.

    Science.gov (United States)

    Rizvi, Mohd Suhail; Pal, Anupam

    2014-09-01

    The fibrous matrices are widely used as scaffolds for the regeneration of load-bearing tissues due to their structural and mechanical similarities with the fibrous components of the extracellular matrix. These scaffolds not only provide the appropriate microenvironment for the residing cells but also act as medium for the transmission of the mechanical stimuli, essential for the tissue regeneration, from macroscopic scale of the scaffolds to the microscopic scale of cells. The requirement of the mechanical loading for the tissue regeneration requires the fibrous scaffolds to be able to sustain the complex three-dimensional mechanical loading conditions. In order to gain insight into the mechanical behavior of the fibrous matrices under large amount of elongation as well as shear, a statistical model has been formulated to study the macroscopic mechanical behavior of the electrospun fibrous matrix and the transmission of the mechanical stimuli from scaffolds to the cells via the constituting fibers. The study establishes the load-deformation relationships for the fibrous matrices for different structural parameters. It also quantifies the changes in the fiber arrangement and tension generated in the fibers with the deformation of the matrix. The model reveals that the tension generated in the fibers on matrix deformation is not homogeneous and hence the cells located in different regions of the fibrous scaffold might experience different mechanical stimuli. The mechanical response of fibrous matrices was also found to be dependent on the aspect ratio of the matrix. Therefore, the model establishes a structure-mechanics interdependence of the fibrous matrices under large deformation, which can be utilized in identifying the appropriate structure and external mechanical loading conditions for the regeneration of load-bearing tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Wage Growth and Job Mobility in the Early Career : Testing a Statistical Discrimination Model of the Gender Wage Gap

    OpenAIRE

    Belley , Philippe; Havet , Nathalie; Lacroix , Guy

    2012-01-01

    The paper focuses on the early career patterns of young male and female workers. It investigates potential dynamic links between statistical discrimination, mobility, tenure and wage profiles. The model assumes that it is more costly for an employer to assess female workers' productivity and that the noise/signal ratio tapers off more rapidly for male workers. These two assumptions yield numerous theoretical predictions pertaining to gender wage gaps. These predictions are tested using data f...

  20. Predicting foraging wading bird populations in Everglades National Park from seasonal hydrologic statistics under different management scenarios

    Science.gov (United States)

    Kwon, Hyun-Han; Lall, Upmanu; Engel, Vic

    2011-09-01

    The ability to map relationships between ecological outcomes and hydrologic conditions in the Everglades National Park (ENP) is a key building block for their restoration program, a primary goal of which is to improve conditions for wading birds. This paper presents a model linking wading bird foraging numbers to hydrologic conditions in the ENP. Seasonal hydrologic statistics derived from a single water level recorder are well correlated with water depths throughout most areas of the ENP, and are effective as predictors of wading bird numbers when using a nonlinear hierarchical Bayesian model to estimate the conditional distribution of bird populations. Model parameters are estimated using a Markov chain Monte Carlo (MCMC) procedure. Parameter and model uncertainty is assessed as a byproduct of the estimation process. Water depths at the beginning of the nesting season, the average dry season water level, and the numbers of reversals from the dry season recession are identified as significant predictors, consistent with the hydrologic conditions considered important in the production and concentration of prey organisms in this system. Long-term hydrologic records at the index location allow for a retrospective analysis (1952-2006) of foraging bird numbers showing low frequency oscillations in response to decadal fluctuations in hydroclimatic conditions. Simulations of water levels at the index location used in the Bayesian model under alternative water management scenarios allow the posterior probability distributions of the number of foraging birds to be compared, thus providing a mechanism for linking management schemes to seasonal rainfall forecasts.

  1. Dynamic PMU Compliance Test under C37.118.1aTM-2014

    DEFF Research Database (Denmark)

    Ghiga, Radu; Wu, Qiuwei; Martin, K.

    2015-01-01

    This paper presents a flexible testing methodology and the dynamic compliance of PMUs as per the new C37.118.1a amendment published in 2014. The test platform consists of test signal generator, a Doble F6150 amplifier, PMUs under test, and a PMU test result analysis kit. The Doble amplifier is used...

  2. Weibull statistics effective area and volume in the ball-on-ring testing method

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund

    2014-01-01

    The ball-on-ring method is together with other biaxial bending methods often used for measuring the strength of plates of brittle materials, because machining defects are remote from the high stresses causing the failure of the specimens. In order to scale the measured Weibull strength...... to geometries relevant for the application of the material, the effective area or volume for the test specimen must be evaluated. In this work analytical expressions for the effective area and volume of the ball-on-ring test specimen is derived. In the derivation the multiaxial stress field has been accounted...

  3. Testing the effectiveness of monolayers under wind and wave conditions.

    Science.gov (United States)

    Palada, C; Schouten, P; Lemckert, C

    2012-01-01

    Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

  4. Relational Aggression and Hostile Attribution Biases: Testing Multiple Statistical Methods and Models

    Science.gov (United States)

    Godleski, Stephanie A.; Ostrov, Jamie M.

    2010-01-01

    The present study used both categorical and dimensional approaches to test the association between relational and physical aggression and hostile intent attributions for both relational and instrumental provocation situations using the National Institute of Child Health and Human Development longitudinal Study of Early Child Care and Youth…

  5. Monitoring and analysis of bovine spongiform encephalopathy (BSE) testing in Denmark using statistical models

    DEFF Research Database (Denmark)

    Paisley, Larry

    2002-01-01

    The evolution of monitoring and surveillance for bovine spongiform encephalopathy (BSE) from the phase of passive surveillance that began in the United Kingdom in 1988 until the present is described. Currently, surveillance for BSE in Europe consists of mass testing of cattle slaughtered for human...

  6. Stiffness modulus of Polyethylene Terephthalate modified asphalt mixture: A statistical analysis of the laboratory testing results

    International Nuclear Information System (INIS)

    Baghaee Moghaddam, Taher; Soltani, Mehrtash; Karim, Mohamed Rehan

    2015-01-01

    Highlights: • Effect of PET modification on stiffness property of asphalt mixture was examined. • Different temperatures and loading amounts were designated. • Statistical analysis was used to find interactions between selected variables. • A good agreement between experimental results and predicted values was obtained. • Optimal amount of PET was calculated to achieve the highest mixture performance. - Abstract: Stiffness of asphalt mixture is a fundamental design parameter of flexible pavement. According to literature, stiffness value is very susceptible to environmental and loading conditions. In this paper, effects of applied stress and temperature on the stiffness modulus of unmodified and Polyethylene Terephthalate (PET) modified asphalt mixtures were evaluated using Response Surface Methodology (RSM). A quadratic model was successfully fitted to the experimental data. Based on the results achieved in this study, the temperature variation had the highest impact on the mixture’s stiffness. Besides, PET content and amount of stress showed to have almost the same effect on the stiffness of mixtures. The optimal amount of PET was found to be 0.41% by weight of aggregate particles to reach the highest stiffness value

  7. Relationship between the COI test and other sensory profiles by statistical procedures

    Directory of Open Access Journals (Sweden)

    Calvente, J. J.

    1994-04-01

    Full Text Available Relationships between 139 sensory attributes evaluated on 32 samples of virgin olive oil have been analysed by a statistical sensory wheel that guarantees the objectiveness and prediction of its conclusions concerning the best clusters of attributes: green, bitter-pungent, ripe fruit, fruity, sweet fruit, undesirable attributes and two miscellanies. The procedure allows the sensory notes evaluated for potential consumers of this edible oil from the point of view of its habitual consumers to be understood with special reference to The European Communities Regulation n-2568/91. Five different panels: Spanish, Greek, Italian, Dutch and British, have been used to evaluate the samples. Analysis of the relationships between stimuli perceived by aroma, flavour, smell, mouthfeel and taste together with Linear Sensory Profiles based on Fuzzy Logic are provided. A 3-dimensional plot indicates the usefulness of the proposed procedure in the authentication of different varieties of virgin olive oil. An analysis of the volatile compounds responsible for most of the attributes gives weight to the conclusions. Directions which promise to improve the E.G. Regulation on the sensory quality of olive oil are also given.

  8. A statistical simulation model for field testing of non-target organisms in environmental risk assessment of genetically modified plants.

    Science.gov (United States)

    Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore

    2014-04-01

    Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided.

  9. Testing for Gender Related Size and Shape Differences of the Human Ear canal using Statistical methods

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Larsen, Rasmus; Ersbøll, Bjarne Kjær

    2002-01-01

    surface models are built by using the anatomical landmarks to warp a template mesh onto all shapes in the training set. Testing the gender related differences is done by initially reducing the dimensionality using principal component analysis of the vertices of the warped meshes. The number of components...... to retain is chosen using Horn's parallel analysis. Finally a multivariate analysis of variance is performed on these components....

  10. A statistical test of the stability assumption inherent in empirical estimates of economic depreciation.

    Science.gov (United States)

    Shriver, K A

    1986-01-01

    Realistic estimates of economic depreciation are required for analyses of tax policy, economic growth and production, and national income and wealth. THe purpose of this paper is to examine the stability assumption underlying the econometric derivation of empirical estimates of economic depreciation for industrial machinery and and equipment. The results suggest that a reasonable stability of economic depreciation rates of decline may exist over time. Thus, the assumption of a constant rate of economic depreciation may be a reasonable approximation for further empirical economic analyses.

  11. Engaging Diverse Students in Statistical Inquiry: A Comparison of Learning Experiences and Outcomes of Under-Represented and Non-Underrepresented Students Enrolled in a Multidisciplinary Project-Based Statistics Course

    Science.gov (United States)

    Dierker, Lisa; Alexander, Jalen; Cooper, Jennifer L.; Selya, Arielle; Rose, Jennifer; Dasgupta, Nilanjana

    2016-01-01

    Introductory statistics needs innovative, evidence-based teaching practices that support and engage diverse students. To evaluate the success of a multidisciplinary, project-based course, we compared experiences of under-represented (URM) and non-underrepresented students in 4 years of the course. While URM students considered the material more…

  12. Application of modern tests for stationarity to single-trial MEG data: transferring powerful statistical tools from econometrics to neuroscience.

    Science.gov (United States)

    Kipiński, Lech; König, Reinhard; Sielużycki, Cezary; Kordecki, Wojciech

    2011-10-01

    Stationarity is a crucial yet rarely questioned assumption in the analysis of time series of magneto- (MEG) or electroencephalography (EEG). One key drawback of the commonly used tests for stationarity of encephalographic time series is the fact that conclusions on stationarity are only indirectly inferred either from the Gaussianity (e.g. the Shapiro-Wilk test or Kolmogorov-Smirnov test) or the randomness of the time series and the absence of trend using very simple time-series models (e.g. the sign and trend tests by Bendat and Piersol). We present a novel approach to the analysis of the stationarity of MEG and EEG time series by applying modern statistical methods which were specifically developed in econometrics to verify the hypothesis that a time series is stationary. We report our findings of the application of three different tests of stationarity--the Kwiatkowski-Phillips-Schmidt-Schin (KPSS) test for trend or mean stationarity, the Phillips-Perron (PP) test for the presence of a unit root and the White test for homoscedasticity--on an illustrative set of MEG data. For five stimulation sessions, we found already for short epochs of duration of 250 and 500 ms that, although the majority of the studied epochs of single MEG trials were usually mean-stationary (KPSS test and PP test), they were classified as nonstationary due to their heteroscedasticity (White test). We also observed that the presence of external auditory stimulation did not significantly affect the findings regarding the stationarity of the data. We conclude that the combination of these tests allows a refined analysis of the stationarity of MEG and EEG time series.

  13. A Systematic Review of Statistical Methods Used to Test for Reliability of Medical Instruments Measuring Continuous Variables

    Directory of Open Access Journals (Sweden)

    Rafdzah Zaki

    2013-06-01

    Full Text Available   Objective(s: Reliability measures precision or the extent to which test results can be replicated. This is the first ever systematic review to identify statistical methods used to measure reliability of equipment measuring continuous variables. This studyalso aims to highlight the inappropriate statistical method used in the reliability analysis and its implication in the medical practice.   Materials and Methods: In 2010, five electronic databases were searched between 2007 and 2009 to look for reliability studies. A total of 5,795 titles were initially identified. Only 282 titles were potentially related, and finally 42 fitted the inclusion criteria. Results: The Intra-class Correlation Coefficient (ICC is the most popular method with 25 (60% studies having used this method followed by the comparing means (8 or 19%. Out of 25 studies using the ICC, only 7 (28% reported the confidence intervals and types of ICC used. Most studies (71% also tested the agreement of instruments. Conclusion: This study finds that the Intra-class Correlation Coefficient is the most popular method used to assess the reliability of medical instruments measuring continuous outcomes. There are also inappropriate applications and interpretations of statistical methods in some studies. It is important for medical researchers to be aware of this issue, and be able to correctly perform analysis in reliability studies.

  14. Age related neuromuscular changes in sEMG of m. Tibialis Anterior using higher order statistics (Gaussianity & linearity test).

    Science.gov (United States)

    Siddiqi, Ariba; Arjunan, Sridhar P; Kumar, Dinesh K

    2016-08-01

    Age-associated changes in the surface electromyogram (sEMG) of Tibialis Anterior (TA) muscle can be attributable to neuromuscular alterations that precede strength loss. We have used our sEMG model of the Tibialis Anterior to interpret the age-related changes and compared with the experimental sEMG. Eighteen young (20-30 years) and 18 older (60-85 years) performed isometric dorsiflexion at 6 different percentage levels of maximum voluntary contractions (MVC), and their sEMG from the TA muscle was recorded. Six different age-related changes in the neuromuscular system were simulated using the sEMG model at the same MVCs as the experiment. The maximal power of the spectrum, Gaussianity and Linearity Test Statistics were computed from the simulated and experimental sEMG. A correlation analysis at α=0.05 was performed between the simulated and experimental age-related change in the sEMG features. The results show the loss in motor units was distinguished by the Gaussianity and Linearity test statistics; while the maximal power of the PSD distinguished between the muscular factors. The simulated condition of 40% loss of motor units with halved the number of fast fibers best correlated with the age-related change observed in the experimental sEMG higher order statistical features. The simulated aging condition found by this study corresponds with the moderate motor unit remodelling and negligible strength loss reported in literature for the cohorts aged 60-70 years.

  15. Automated collimation testing by determining the statistical correlation coefficient of Talbot self-images.

    Science.gov (United States)

    Rana, Santosh; Dhanotia, Jitendra; Bhatia, Vimal; Prakash, Shashi

    2018-04-01

    In this paper, we propose a simple, fast, and accurate technique for detection of collimation position of an optical beam using the self-imaging phenomenon and correlation analysis. Herrera-Fernandez et al. [J. Opt.18, 075608 (2016)JOOPDB0150-536X10.1088/2040-8978/18/7/075608] proposed an experimental arrangement for collimation testing by comparing the period of two different self-images produced by a single diffraction grating. Following their approach, we propose a testing procedure based on correlation coefficient (CC) for efficient detection of variation in the size and fringe width of the Talbot self-images and thereby the collimation position. When the beam is collimated, the physical properties of the self-images of the grating, such as its size and fringe width, do not vary from one Talbot plane to the other and are identical; the CC is maximum in such a situation. For the de-collimated position, the size and fringe width of the self-images vary, and correspondingly the CC decreases. Hence, the magnitude of CC is a measure of degree of collimation. Using the method, we could set the collimation position to a resolution of 1 μm, which relates to ±0.25   μ    radians in terms of collimation angle (for testing a collimating lens of diameter 46 mm and focal length 300 mm). In contrast to most collimation techniques reported to date, the proposed technique does not require a translation/rotation of the grating, use of complicated phase evaluation algorithms, or an intricate method for determination of period of the grating or its self-images. The technique is fully automated and provides high resolution and precision.

  16. Local tolerance testing under REACH: Accepted non-animal methods are not on equal footing with animal tests.

    Science.gov (United States)

    Sauer, Ursula G; Hill, Erin H; Curren, Rodger D; Raabe, Hans A; Kolle, Susanne N; Teubner, Wera; Mehling, Annette; Landsiedel, Robert

    2016-07-01

    In general, no single non-animal method can cover the complexity of any given animal test. Therefore, fixed sets of in vitro (and in chemico) methods have been combined into testing strategies for skin and eye irritation and skin sensitisation testing, with pre-defined prediction models for substance classification. Many of these methods have been adopted as OECD test guidelines. Various testing strategies have been successfully validated in extensive in-house and inter-laboratory studies, but they have not yet received formal acceptance for substance classification. Therefore, under the European REACH Regulation, data from testing strategies can, in general, only be used in so-called weight-of-evidence approaches. While animal testing data generated under the specific REACH information requirements are per se sufficient, the sufficiency of weight-of-evidence approaches can be questioned under the REACH system, and further animal testing can be required. This constitutes an imbalance between the regulatory acceptance of data from approved non-animal methods and animal tests that is not justified on scientific grounds. To ensure that testing strategies for local tolerance testing truly serve to replace animal testing for the REACH registration 2018 deadline (when the majority of existing chemicals have to be registered), clarity on their regulatory acceptance as complete replacements is urgently required. 2016 FRAME.

  17. On the Integrity of Online Testing for Introductory Statistics Courses: A Latent Variable Approach

    Directory of Open Access Journals (Sweden)

    Alan Fask

    2015-04-01

    Full Text Available There has been a remarkable growth in distance learning courses in higher education. Despite indications that distance learning courses are more vulnerable to cheating behavior than traditional courses, there has been little research studying whether online exams facilitate a relatively greater level of cheating. This article examines this issue by developing an approach using a latent variable to measure student cheating. This latent variable is linked to both known student mastery related variables and variables unrelated to student mastery. Grade scores from a proctored final exam and an unproctored final exam are used to test for increased cheating behavior in the unproctored exam

  18. An empirical test of Maslow's theory of need hierarchy using hologeistic comparison by statistical sampling.

    Science.gov (United States)

    Davis-Sharts, J

    1986-10-01

    Maslow's hierarchy of basic human needs provides a major theoretical framework in nursing science. The purpose of this study was to empirically test Maslow's need theory, specifically at the levels of physiological and security needs, using a hologeistic comparative method. Thirty cultures taken from the 60 cultural units in the Health Relations Area Files (HRAF) Probability Sample were found to have data available for examining hypotheses about thermoregulatory (physiological) and protective (security) behaviors practiced prior to sleep onset. The findings demonstrate there is initial worldwide empirical evidence to support Maslow's need hierarchy.

  19. Expansions of GMM statistics that indicate their properties under weak and/or many instruments and the bootstrap

    NARCIS (Netherlands)

    Kleibergen, F.R.

    2003-01-01

    We show that the sensitivity of the limit distribution of commonly used GMM statistics to weak and many instruments results from superfluous elements in the higher order expansion of these statistics. When the instruments are strong and their number is small, these elements are of higher order and

  20. Designing experiments for maximum information from cyclic oxidation tests and their statistical analysis using half Normal plots

    International Nuclear Information System (INIS)

    Coleman, S.Y.; Nicholls, J.R.

    2006-01-01

    Cyclic oxidation testing at elevated temperatures requires careful experimental design and the adoption of standard procedures to ensure reliable data. This is a major aim of the 'COTEST' research programme. Further, as such tests are both time consuming and costly, in terms of human effort, to take measurements over a large number of cycles, it is important to gain maximum information from a minimum number of tests (trials). This search for standardisation of cyclic oxidation conditions leads to a series of tests to determine the relative effects of cyclic parameters on the oxidation process. Following a review of the available literature, databases and the experience of partners to the COTEST project, the most influential parameters, upper dwell temperature (oxidation temperature) and time (hot time), lower dwell time (cold time) and environment, were investigated in partners' laboratories. It was decided to test upper dwell temperature at 3 levels, at and equidistant from a reference temperature; to test upper dwell time at a reference, a higher and a lower time; to test lower dwell time at a reference and a higher time and wet and dry environments. Thus an experiment, consisting of nine trials, was designed according to statistical criteria. The results of the trial were analysed statistically, to test the main linear and quadratic effects of upper dwell temperature and hot time and the main effects of lower dwell time (cold time) and environment. The nine trials are a quarter fraction of the 36 possible combinations of parameter levels that could have been studied. The results have been analysed by half Normal plots as there are only 2 degrees of freedom for the experimental error variance, which is rather low for a standard analysis of variance. Half Normal plots give a visual indication of which factors are statistically significant. In this experiment each trial has 3 replications, and the data are analysed in terms of mean mass change, oxidation kinetics

  1. A generalized Grubbs-Beck test statistic for detecting multiple potentially influential low outliers in flood series

    Science.gov (United States)

    Cohn, T.A.; England, J.F.; Berenbrock, C.E.; Mason, R.R.; Stedinger, J.R.; Lamontagne, J.R.

    2013-01-01

    he Grubbs-Beck test is recommended by the federal guidelines for detection of low outliers in flood flow frequency computation in the United States. This paper presents a generalization of the Grubbs-Beck test for normal data (similar to the Rosner (1983) test; see also Spencer and McCuen (1996)) that can provide a consistent standard for identifying multiple potentially influential low flows. In cases where low outliers have been identified, they can be represented as “less-than” values, and a frequency distribution can be developed using censored-data statistical techniques, such as the Expected Moments Algorithm. This approach can improve the fit of the right-hand tail of a frequency distribution and provide protection from lack-of-fit due to unimportant but potentially influential low flows (PILFs) in a flood series, thus making the flood frequency analysis procedure more robust.

  2. Accuracy statistics in predicting Independent Activities of Daily Living (IADL) capacity with comprehensive and brief neuropsychological test batteries.

    Science.gov (United States)

    Karzmark, Peter; Deutsch, Gayle K

    2018-01-01

    This investigation was designed to determine the predictive accuracy of a comprehensive neuropsychological and brief neuropsychological test battery with regard to the capacity to perform instrumental activities of daily living (IADLs). Accuracy statistics that included measures of sensitivity, specificity, positive and negative predicted power and positive likelihood ratio were calculated for both types of batteries. The sample was drawn from a general neurological group of adults (n = 117) that included a number of older participants (age >55; n = 38). Standardized neuropsychological assessments were administered to all participants and were comprised of the Halstead Reitan Battery and portions of the Wechsler Adult Intelligence Scale-III. A comprehensive test battery yielded a moderate increase over base-rate in predictive accuracy that generalized to older individuals. There was only limited support for using a brief battery, for although sensitivity was high, specificity was low. We found that a comprehensive neuropsychological test battery provided good classification accuracy for predicting IADL capacity.

  3. Change detection in a time series of polarimetric SAR data by an omnibus test statistic and its factorization (Conference Presentation)

    Science.gov (United States)

    Nielsen, Allan A.; Conradsen, Knut; Skriver, Henning

    2016-10-01

    Test statistics for comparison of real (as opposed to complex) variance-covariance matrices exist in the statistics literature [1]. In earlier publications we have described a test statistic for the equality of two variance-covariance matrices following the complex Wishart distribution with an associated p-value [2]. We showed their application to bitemporal change detection and to edge detection [3] in multilook, polarimetric synthetic aperture radar (SAR) data in the covariance matrix representation [4]. The test statistic and the associated p-value is described in [5] also. In [6] we focussed on the block-diagonal case, we elaborated on some computer implementation issues, and we gave examples on the application to change detection in both full and dual polarization bitemporal, bifrequency, multilook SAR data. In [7] we described an omnibus test statistic Q for the equality of k variance-covariance matrices following the complex Wishart distribution. We also described a factorization of Q = R2 R3 … Rk where Q and Rj determine if and when a difference occurs. Additionally, we gave p-values for Q and Rj. Finally, we demonstrated the use of Q and Rj and the p-values to change detection in truly multitemporal, full polarization SAR data. Here we illustrate the methods by means of airborne L-band SAR data (EMISAR) [8,9]. The methods may be applied to other polarimetric SAR data also such as data from Sentinel-1, COSMO-SkyMed, TerraSAR-X, ALOS, and RadarSat-2 and also to single-pol data. The account given here closely follows that given our recent IEEE TGRS paper [7]. Selected References [1] Anderson, T. W., An Introduction to Multivariate Statistical Analysis, John Wiley, New York, third ed. (2003). [2] Conradsen, K., Nielsen, A. A., Schou, J., and Skriver, H., "A test statistic in the complex Wishart distribution and its application to change detection in polarimetric SAR data," IEEE Transactions on Geoscience and Remote Sensing 41(1): 4-19, 2003. [3] Schou, J

  4. Reply: Birnbaum's (2012 statistical tests of independence have unknown Type-I error rates and do not replicate within participant

    Directory of Open Access Journals (Sweden)

    Yun-shil Cha

    2013-01-01

    Full Text Available Birnbaum (2011, 2012 questioned the iid (independent and identically distributed sampling assumptions used by state-of-the-art statistical tests in Regenwetter, Dana and Davis-Stober's (2010, 2011 analysis of the ``linear order model''. Birnbaum (2012 cited, but did not use, a test of iid by Smith and Batchelder (2008 with analytically known properties. Instead, he created two new test statistics with unknown sampling distributions. Our rebuttal has five components: 1 We demonstrate that the Regenwetter et al. data pass Smith and Batchelder's test of iid with flying colors. 2 We provide evidence from Monte Carlo simulations that Birnbaum's (2012 proposed tests have unknown Type-I error rates, which depend on the actual choice probabilities and on how data are coded as well as on the null hypothesis of iid sampling. 3 Birnbaum analyzed only a third of Regenwetter et al.'s data. We show that his two new tests fail to replicate on the other two-thirds of the data, within participants. 4 Birnbaum selectively picked data of one respondent to suggest that choice probabilities may have changed partway into the experiment. Such nonstationarity could potentially cause a seemingly good fit to be a Type-II error. We show that the linear order model fits equally well if we allow for warm-up effects. 5 Using hypothetical data, Birnbaum (2012 claimed to show that ``true-and-error'' models for binary pattern probabilities overcome the alleged short-comings of Regenwetter et al.'s approach. We disprove this claim on the same data.

  5. Statistical analysis on the fluence factor of surveillance test data of Korean nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gyeong Geun; Kim, Min Chul; Yoon, Ji Hyun; Lee, Bong Sang; Lim, Sang Yeob; Kwon, Jun Hyun [Nuclear Materials Safety Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-06-15

    The transition temperature shift (TTS) of the reactor pressure vessel materials is an important factor that determines the lifetime of a nuclear power plant. The prediction of the TTS at the end of a plant’s lifespan is calculated based on the equation of Regulatory Guide 1.99 revision 2 (RG1.99/2) from the US. The fluence factor in the equation was expressed as a power function, and the exponent value was determined by the early surveillance data in the US. Recently, an advanced approach to estimate the TTS was proposed in various countries for nuclear power plants, and Korea is considering the development of a new TTS model. In this study, the TTS trend of the Korean surveillance test results was analyzed using a nonlinear regression model and a mixed-effect model based on the power function. The nonlinear regression model yielded a similar exponent as the power function in the fluence compared with RG1.99/2. The mixed-effect model had a higher value of the exponent and showed superior goodness of fit compared with the nonlinear regression model. Compared with RG1.99/2 and RG1.99/3, the mixed-effect model provided a more accurate prediction of the TTS.

  6. Statistical equivalence and test-retest reliability of delay and probability discounting using real and hypothetical rewards.

    Science.gov (United States)

    Matusiewicz, Alexis K; Carter, Anne E; Landes, Reid D; Yi, Richard

    2013-11-01

    Delay discounting (DD) and probability discounting (PD) refer to the reduction in the subjective value of outcomes as a function of delay and uncertainty, respectively. Elevated measures of discounting are associated with a variety of maladaptive behaviors, and confidence in the validity of these measures is imperative. The present research examined (1) the statistical equivalence of discounting measures when rewards were hypothetical or real, and (2) their 1-week reliability. While previous research has partially explored these issues using the low threshold of nonsignificant difference, the present study fully addressed this issue using the more-compelling threshold of statistical equivalence. DD and PD measures were collected from 28 healthy adults using real and hypothetical $50 rewards during each of two experimental sessions, one week apart. Analyses using area-under-the-curve measures revealed a general pattern of statistical equivalence, indicating equivalence of real/hypothetical conditions as well as 1-week reliability. Exceptions are identified and discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. GENUS STATISTICS USING THE DELAUNAY TESSELLATION FIELD ESTIMATION METHOD. I. TESTS WITH THE MILLENNIUM SIMULATION AND THE SDSS DR7

    International Nuclear Information System (INIS)

    Zhang Youcai; Yang Xiaohu; Springel, Volker

    2010-01-01

    We study the topology of cosmic large-scale structure through the genus statistics, using galaxy catalogs generated from the Millennium Simulation and observational data from the latest Sloan Digital Sky Survey Data Release (SDSS DR7). We introduce a new method for constructing galaxy density fields and for measuring the genus statistics of its isodensity surfaces. It is based on a Delaunay tessellation field estimation (DTFE) technique that allows the definition of a piece-wise continuous density field and the exact computation of the topology of its polygonal isodensity contours, without introducing any free numerical parameter. Besides this new approach, we also employ the traditional approaches of smoothing the galaxy distribution with a Gaussian of fixed width, or by adaptively smoothing with a kernel that encloses a constant number of neighboring galaxies. Our results show that the Delaunay-based method extracts the largest amount of topological information. Unlike the traditional approach for genus statistics, it is able to discriminate between the different theoretical galaxy catalogs analyzed here, both in real space and in redshift space, even though they are based on the same underlying simulation model. In particular, the DTFE approach detects with high confidence a discrepancy of one of the semi-analytic models studied here compared with the SDSS data, while the other models are found to be consistent.

  8. Automated grading of homework assignments and tests in introductory and intermediate statistics courses using active server pages.

    Science.gov (United States)

    Stockburger, D W

    1999-05-01

    Active server pages permit a software developer to customize the Web experience for users by inserting server-side script and database access into Web pages. This paper describes applications of these techniques and provides a primer on the use of these methods. Applications include a system that generates and grades individualized homework assignments and tests for statistics students. The student accesses the system as a Web page, prints out the assignment, does the assignment, and enters the answers on the Web page. The server, running on NT Server 4.0, grades the assignment, updates the grade book (on a database), and returns the answer key to the student.

  9. Statistical properties of SASE FEL radiation: experimental results from the VUV FEL at the TESLA test facility at DESY

    International Nuclear Information System (INIS)

    Yurkov, M.V.

    2002-01-01

    This paper presents an experimental study of the statistical properties of the radiation from a SASE FEL. The experiments were performed at the TESLA Test Facility VUV SASE FEL at DESY operating in a high-gain linear regime with a gain of about 10 6 . It is shown that fluctuations of the output radiation energy follows a gamma-distribution. We also measured for the first time the probability distribution of SASE radiation energy after a narrow-band monochromator. The experimental results are in good agreement with theoretical predictions, the energy fluctuations after the monochromator follow a negative exponential distribution

  10. A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated

    OpenAIRE

    Sandurska, Elżbieta; Szulc, Aleksandra

    2016-01-01

    Sandurska Elżbieta, Szulc Aleksandra. A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated. Journal of Education Health and Sport. 2016;6(13):275-287. eISSN 2391-8306. DOI http://dx.doi.org/10.5281/zenodo.293762 http://ojs.ukw.edu.pl/index.php/johs/article/view/4278 The journal has had 7 points in Ministry of Science and Higher Education parametric evaluation. Part B item 754 (09.12.2016). 754 Journal...

  11. Bending fatigue tests on SiC-Al tapes under alternating stress at room temperature

    Science.gov (United States)

    Herzog, J. A.

    1981-01-01

    The development of a testing method for fatigue tests on SiC-Al tapes containing a small amount of SiC filaments under alternating stress is reported. The fatigue strength curves resulting for this composite are discussed. They permit an estimate of its behavior under continuous stress and in combination with various other matrices, especially metal matrices.

  12. RILEM technical committee 195-DTD recommendation for test methods for AD and TD of early age concrete Round Robin documentation report : program, test results and statistical evaluation

    CERN Document Server

    Bjøntegaard, Øyvind; Krauss, Matias; Budelmann, Harald

    2015-01-01

    This report presents the Round-Robin (RR) program and test results including a statistical evaluation of the RILEM TC195-DTD committee named “Recommendation for test methods for autogenous deformation (AD) and thermal dilation (TD) of early age concrete”. The task of the committee was to investigate the linear test set-up for AD and TD measurements (Dilation Rigs) in the period from setting to the end of the hardening phase some weeks after. These are the stress-inducing deformations in a hardening concrete structure subjected to restraint conditions. The main task was to carry out an RR program on testing of AD of one concrete at 20 °C isothermal conditions in Dilation Rigs. The concrete part materials were distributed to 10 laboratories (Canada, Denmark, France, Germany, Japan, The Netherlands, Norway, Sweden and USA), and in total 30 tests on AD were carried out. Some supporting tests were also performed, as well as a smaller RR on cement paste. The committee has worked out a test procedure recommenda...

  13. Statistical flaw strength distributions for glass fibres: Correlation between bundle test and AFM-derived flaw size density functions

    International Nuclear Information System (INIS)

    Foray, G.; Descamps-Mandine, A.; R’Mili, M.; Lamon, J.

    2012-01-01

    The present paper investigates glass fibre flaw size distributions. Two commercial fibre grades (HP and HD) mainly used in cement-based composite reinforcement were studied. Glass fibre fractography is a difficult and time consuming exercise, and thus is seldom carried out. An approach based on tensile tests on multifilament bundles and examination of the fibre surface by atomic force microscopy (AFM) was used. Bundles of more than 500 single filaments each were tested. Thus a statistically significant database of failure data was built up for the HP and HD glass fibres. Gaussian flaw distributions were derived from the filament tensile strength data or extracted from the AFM images. The two distributions were compared. Defect sizes computed from raw AFM images agreed reasonably well with those derived from tensile strength data. Finally, the pertinence of a Gaussian distribution was discussed. The alternative Pareto distribution provided a fair approximation when dealing with AFM flaw size.

  14. Statistical analysis and ANN modeling for predicting hydrological extremes under climate change scenarios: the example of a small Mediterranean agro-watershed.

    Science.gov (United States)

    Kourgialas, Nektarios N; Dokou, Zoi; Karatzas, George P

    2015-05-01

    The purpose of this study was to create a modeling management tool for the simulation of extreme flow events under current and future climatic conditions. This tool is a combination of different components and can be applied in complex hydrogeological river basins, where frequent flood and drought phenomena occur. The first component is the statistical analysis of the available hydro-meteorological data. Specifically, principal components analysis was performed in order to quantify the importance of the hydro-meteorological parameters that affect the generation of extreme events. The second component is a prediction-forecasting artificial neural network (ANN) model that simulates, accurately and efficiently, river flow on an hourly basis. This model is based on a methodology that attempts to resolve a very difficult problem related to the accurate estimation of extreme flows. For this purpose, the available measurements (5 years of hourly data) were divided in two subsets: one for the dry and one for the wet periods of the hydrological year. This way, two ANNs were created, trained, tested and validated for a complex Mediterranean river basin in Crete, Greece. As part of the second management component a statistical downscaling tool was used for the creation of meteorological data according to the higher and lower emission climate change scenarios A2 and B1. These data are used as input in the ANN for the forecasting of river flow for the next two decades. The final component is the application of a meteorological index on the measured and forecasted precipitation and flow data, in order to assess the severity and duration of extreme events. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Under sodium reliability tests on core components and in-core instrumentation

    International Nuclear Information System (INIS)

    Ruppert, E.; Stehle, H.; Vinzens, K.

    1977-01-01

    A sodium test facility for fast breeder core components (AKB), built by INTERATOM at Bensberg, has been operating since 1971 to test fuel dummies and blanket elements as well as absorber elements under simulated normal and extreme reactor conditions. Individual full-scale fuel or blanket elements and arrays of seven elements, modelling a section of the SNR-300 reactor core, have been tested under a wide range of sodium mass flow and isothermal test conditions up to 925K as well as under cyclic changed temperature transients. Besides endurance testing of the core components a special sodium and high-temperature instrumentation is provided to investigate thermohydraulic and vibrational behaviour of the test objects. During all test periods the main subassembly characteristics could be reproduced and the reliability of the instrumentation could be proven. (orig.) [de

  16. Validity and reliability of new agility test among elite and subelite under 14-soccer players.

    Directory of Open Access Journals (Sweden)

    Younés Hachana

    Full Text Available BACKGROUND: Agility is a determinant component in soccer performance. This study aimed to evaluate the reliability and sensitivity of a "Modified Illinois change of direction test" (MICODT in ninety-five U-14 soccer players. METHODS: A total of 95 U-14 soccer players (mean ± SD: age: 13.61 ± 1.04 years; body mass: 30.52 ± 4.54 kg; height: 1.57 ± 0.1 m from a professional and semi-professional soccer academy, participated to this study. Sixty of them took part in reliability analysis and thirty-two in sensitivity analysis. RESULTS: The intraclass correlation coefficient (ICC that aims to assess relative reliability of the MICODT was of 0.99, and its standard error of measurement (SEM for absolute reliability was <5% (1.24%. The MICODT's capacity to detect change is "good", it's SEM (0.10 s was ≤ SWC (0.33 s. The MICODT is significantly correlated to the Illinois change of direction speed test (ICODT (r = 0.77; p<0.0001. The ICODT's MDC95 (0.64 s was twice about the MICODT's MDC95 (0.28 s, indicating that MICODT presents better ability to detect true changes than ICODT. The MICODT provided good sensitivity since elite U-14 soccer players were better than non-elite one on MICODT (p = 0.005; dz = 1.01 [large]. This was supported by an area under the ROC curve of 0.77 (CI 95%, 0.59 to 0.89, p<0.0008. The difference observed in these two groups in ICODT was not statistically significant (p = 0.14; dz = 0.51 [small], showing poor discriminant ability. CONCLUSION: MICODT can be considered as more suitable protocol for assessing agility performance level than ICODT in U-14 soccer players.

  17. Homogeneity tests for variances and mean test under heterogeneity conditions in a single way ANOVA method

    International Nuclear Information System (INIS)

    Morales P, J.R.; Avila P, P.

    1996-01-01

    If we have consider the maximum permissible levels showed for the case of oysters, it results forbidding to collect oysters at the four stations of the El Chijol Channel ( Veracruz, Mexico), as well as along the channel itself, because the metal concentrations studied exceed these limits. In this case the application of Welch tests were not necessary. For the water hyacinth the means of the treatments were unequal in Fe, Cu, Ni, and Zn. This case is more illustrative, for the conclusion has been reached through the application of the Welch tests to treatments with heterogeneous variances. (Author)

  18. Test of safety injection supply by diesel generator under reactor vessel closed condition

    International Nuclear Information System (INIS)

    Zhang Hao; Bi Fengchuan; Che Junxia; Zhang Jianwen; Yang Bo

    2014-01-01

    The paper studied that the test of diesel generator full load take-up under the condition of actual safety injection and reactor vessel closed in Ningde nuclear project unit l. It is proved that test result accorded with design criteria, meanwhile, the test was removed from the key path of project schedule, which cut a huge cost. (authors)

  19. 77 FR 15101 - Results From Inert Ingredient Test Orders Issued Under EPA's Endocrine Disruptor Screening...

    Science.gov (United States)

    2012-03-14

    ... the selection criteria for endocrine testing under the Safe Drinking Water Act (SDWA). EPA has no...) because the chemicals meet the selection criteria. EPA has no plans to issue further test orders for the... Screening Program (EDSP) and the Federal Food, Drug, and Cosmetic Act (FFDCA). In response to the test...

  20. FLUCTUATION IN PENSION FUND ASSETS PRIVATELY MANAGED UNDER THE INFLUENCE OF CERTAIN FACTORS. STATISTICAL STUDY IN ROMANIA

    Directory of Open Access Journals (Sweden)

    Dracea Raluca

    2011-07-01

    Full Text Available On international level, the economic and financial crisis has determined a diminution of the asset value of compulsory pension funds, reflecting a reallocation of funds towards alternative or low-risk investments. The present paper indicates how the net asset value of privately managed pension funds in Romania may be affected or not by certain influence factors in direct correlation with different asset allocation strategies of pension funds. In this way, on literature review there are many studies which have analyzed the fluctuation of pension funds assets and a better reallocation of their investment in order to improve their efficiency. The experience of the value fluctuation of privately administered pension fund net assets is highly important, firstly beacause of its effects on the increase and the decrease of invested values for the insured persons’ accounts, under the circumstances of constantly maintaining their contributions and, implicitly, the results achieved through these investments. The research methodology consists in testing of five variables: currency exchange rate, credit interest rate, bank deposit interest rate, reference interest rate and value of the stock exchange market index (BET-C index, by means of the multiple linear regression method. The conclusion is that only two of these factors, namely, the currency exchange rate and the reference interest rate, influence net asset value of privately managed pension funds, the second pillar, one in direct and the other in indirect correlation. In order to neutralize the effects generated by the diminution of the net asset value of privately managed pension funds, considering a short time horizon, we shall elaborate a dynamic mix of their investments able to adapt to the fluctuations of the influence factors. Thus, new opportunities will be generated in order to achieve the efficiency of pension funds and to prevent the diminution of the value of insured individuals

  1. Statistical analysis of water-quality data containing multiple detection limits II: S-language software for nonparametric distribution modeling and hypothesis testing

    Science.gov (United States)

    Lee, L.; Helsel, D.

    2007-01-01

    Analysis of low concentrations of trace contaminants in environmental media often results in left-censored data that are below some limit of analytical precision. Interpretation of values becomes complicated when there are multiple detection limits in the data-perhaps as a result of changing analytical precision over time. Parametric and semi-parametric methods, such as maximum likelihood estimation and robust regression on order statistics, can be employed to model distributions of multiply censored data and provide estimates of summary statistics. However, these methods are based on assumptions about the underlying distribution of data. Nonparametric methods provide an alternative that does not require such assumptions. A standard nonparametric method for estimating summary statistics of multiply-censored data is the Kaplan-Meier (K-M) method. This method has seen widespread usage in the medical sciences within a general framework termed "survival analysis" where it is employed with right-censored time-to-failure data. However, K-M methods are equally valid for the left-censored data common in the geosciences. Our S-language software provides an analytical framework based on K-M methods that is tailored to the needs of the earth and environmental sciences community. This includes routines for the generation of empirical cumulative distribution functions, prediction or exceedance probabilities, and related confidence limits computation. Additionally, our software contains K-M-based routines for nonparametric hypothesis testing among an unlimited number of grouping variables. A primary characteristic of K-M methods is that they do not perform extrapolation and interpolation. Thus, these routines cannot be used to model statistics beyond the observed data range or when linear interpolation is desired. For such applications, the aforementioned parametric and semi-parametric methods must be used.

  2. Exploiting the full power of temporal gene expression profiling through a new statistical test: Application to the analysis of muscular dystrophy data

    Directory of Open Access Journals (Sweden)

    Turk Rolf

    2006-04-01

    Full Text Available Abstract Background The identification of biologically interesting genes in a temporal expression profiling dataset is challenging and complicated by high levels of experimental noise. Most statistical methods used in the literature do not fully exploit the temporal ordering in the dataset and are not suited to the case where temporal profiles are measured for a number of different biological conditions. We present a statistical test that makes explicit use of the temporal order in the data by fitting polynomial functions to the temporal profile of each gene and for each biological condition. A Hotelling T2-statistic is derived to detect the genes for which the parameters of these polynomials are significantly different from each other. Results We validate the temporal Hotelling T2-test on muscular gene expression data from four mouse strains which were profiled at different ages: dystrophin-, beta-sarcoglycan and gamma-sarcoglycan deficient mice, and wild-type mice. The first three are animal models for different muscular dystrophies. Extensive biological validation shows that the method is capable of finding genes with temporal profiles significantly different across the four strains, as well as identifying potential biomarkers for each form of the disease. The added value of the temporal test compared to an identical test which does not make use of temporal ordering is demonstrated via a simulation study, and through confirmation of the expression profiles from selected genes by quantitative PCR experiments. The proposed method maximises the detection of the biologically interesting genes, whilst minimising false detections. Conclusion The temporal Hotelling T2-test is capable of finding relatively small and robust sets of genes that display different temporal profiles between the conditions of interest. The test is simple, it can be used on gene expression data generated from any experimental design and for any number of conditions, and it

  3. TESTING MODELS OF MAGNETIC FIELD EVOLUTION OF NEUTRON STARS WITH THE STATISTICAL PROPERTIES OF THEIR SPIN EVOLUTIONS

    International Nuclear Information System (INIS)

    Zhang Shuangnan; Xie Yi

    2012-01-01

    We test models for the evolution of neutron star (NS) magnetic fields (B). Our model for the evolution of the NS spin is taken from an analysis of pulsar timing noise presented by Hobbs et al.. We first test the standard model of a pulsar's magnetosphere in which B does not change with time and magnetic dipole radiation is assumed to dominate the pulsar's spin-down. We find that this model fails to predict both the magnitudes and signs of the second derivatives of the spin frequencies (ν-double dot). We then construct a phenomenological model of the evolution of B, which contains a long-term decay (LTD) modulated by short-term oscillations; a pulsar's spin is thus modified by its B-evolution. We find that an exponential LTD is not favored by the observed statistical properties of ν-double dot for young pulsars and fails to explain the fact that ν-double dot is negative for roughly half of the old pulsars. A simple power-law LTD can explain all the observed statistical properties of ν-double dot. Finally, we discuss some physical implications of our results to models of the B-decay of NSs and suggest reliable determination of the true ages of many young NSs is needed, in order to constrain further the physical mechanisms of their B-decay. Our model can be further tested with the measured evolutions of ν-dot and ν-double dot for an individual pulsar; the decay index, oscillation amplitude, and period can also be determined this way for the pulsar.

  4. Statistical comparative study on a combined radioiodine test and extended protirelin test and correlation with the common in vitro parameters of hyroid function

    International Nuclear Information System (INIS)

    Kraemer, H.A.

    1982-01-01

    Using the data of 339 patients, the following parameters of thyroid function were statistically evaluated. The in vitro parameters ET 3 U, TT 4 (D), FT 4 -index and PB 127 I and the radioiodine test with determination of PB 131 I before i.v. injection of 400 μg protirelin (DHP) and 120 minutes after the injection. There was no correlation between the percentage Change of the PB 121 I level 120 min after protirelin (DHP) administration and the percentage change of the TSH level 30 min after protirelin (DTP1) administration. The accuracies of the in vitro parameters ET 3 U, TT 4 (D) and FT 4 -index on the one hand and the extended protirelin test on the other hand were compared. (orig./MG) [de

  5. Combined equations for estimating global solar radiation: Projection of radiation field over Japan under global warming conditions by statistical downscaling

    International Nuclear Information System (INIS)

    Iizumi, T.; Nishimori, M.; Yokozawa, M.

    2008-01-01

    For this study, we developed a new statistical model to estimate the daily accumulated global solar radiation on the earth's surface and used the model to generate a high-resolution climate change scenario of the radiation field in Japan. The statistical model mainly relies on precipitable water vapor calculated from air temperature and relative humidity on the surface to estimate seasonal changes in global solar radiation. On the other hand, to estimate daily radiation fluctuations, the model uses either a diurnal temperature range or relative humidity. The diurnal temperature range, calculated from the daily maximum and minimum temperatures, and relative humidity is a general output of most climate models, and pertinent observation data are comparatively easy to access. The statistical model performed well when estimating the monthly mean value, daily fluctuation statistics, and regional differences in the radiation field in Japan. To project the change in the radiation field for the years 2081 to 2100, we applied the statistical model to the climate change scenario of a high-resolution Regional Climate Model with a 20-km mesh size (RCM20) developed at the Meteorological Research Institute based on the Special Report for Emission Scenario (SRES)-A2. The projected change shows the following tendency: global solar radiation will increase in the warm season and decrease in the cool season in many areas of Japan, indicating that global warming may cause changes in the radiation field in Japan. The generated climate change scenario for the radiation field is linked to long-term and short-term changes in air temperature and relative humidity obtained from the RCM20 and, consequently, is expected to complement the RCM20 datasets for an impact assessment study in the agricultural sector

  6. Understanding Statistics - Cancer Statistics

    Science.gov (United States)

    Annual reports of U.S. cancer statistics including new cases, deaths, trends, survival, prevalence, lifetime risk, and progress toward Healthy People targets, plus statistical summaries for a number of common cancer types.

  7. A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions

    Science.gov (United States)

    Evans, Mark

    2016-12-01

    A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linear relationship that appears to exist between various creep properties and a log transformation of the normalized stress. However, these linear trends are subject to discontinuities, the number of which appears to differ from material to material. These discontinuities have until now been (1) treated as abrupt in nature and (2) identified by eye from an inspection of simple graphical plots of the data. This article puts forward a statistical test for determining the correct number of discontinuities present within a creep data set and a method for allowing these discontinuities to occur more gradually, so that the methodology is more in line with the accepted view as to how creep mechanisms evolve with changing test conditions. These two developments are fully illustrated using creep data sets on two steel alloys. When these new procedures are applied to these steel alloys, not only do they produce more accurate and realistic looking long-term predictions of the minimum creep rate, but they also lead to different conclusions about the mechanisms determining the rates of creep from those originally put forward by Wilshire.

  8. Experimental observations of Lagrangian sand grain kinematics under bedload transport: statistical description of the step and rest regimes

    Science.gov (United States)

    Guala, M.; Liu, M.

    2017-12-01

    The kinematics of sediment particles is investigated by non-intrusive imaging methods to provide a statistical description of bedload transport in conditions near the threshold of motion. In particular, we focus on the cyclic transition between motion and rest regimes to quantify the waiting time statistics inferred to be responsible for anomalous diffusion, and so far elusive. Despite obvious limitations in the spatio-temporal domain of the observations, we are able to identify the probability distributions of the particle step time and length, velocity, acceleration, waiting time, and thus distinguish which quantities exhibit well converged mean values, based on the thickness of their respective tails. The experimental results shown here for four different transport conditions highlight the importance of the waiting time distribution and represent a benchmark dataset for the stochastic modeling of bedload transport.

  9. Principal Components of Superhigh-Dimensional Statistical Features and Support Vector Machine for Improving Identification Accuracies of Different Gear Crack Levels under Different Working Conditions

    Directory of Open Access Journals (Sweden)

    Dong Wang

    2015-01-01

    Full Text Available Gears are widely used in gearbox to transmit power from one shaft to another. Gear crack is one of the most frequent gear fault modes found in industry. Identification of different gear crack levels is beneficial in preventing any unexpected machine breakdown and reducing economic loss because gear crack leads to gear tooth breakage. In this paper, an intelligent fault diagnosis method for identification of different gear crack levels under different working conditions is proposed. First, superhigh-dimensional statistical features are extracted from continuous wavelet transform at different scales. The number of the statistical features extracted by using the proposed method is 920 so that the extracted statistical features are superhigh dimensional. To reduce the dimensionality of the extracted statistical features and generate new significant low-dimensional statistical features, a simple and effective method called principal component analysis is used. To further improve identification accuracies of different gear crack levels under different working conditions, support vector machine is employed. Three experiments are investigated to show the superiority of the proposed method. Comparisons with other existing gear crack level identification methods are conducted. The results show that the proposed method has the highest identification accuracies among all existing methods.

  10. Statistics Clinic

    Science.gov (United States)

    Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James

    2014-01-01

    Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.

  11. Paired preference data with a no-preference option – Statistical tests for comparison with placebo data

    DEFF Research Database (Denmark)

    Christensen, Rune Haubo Bojesen; Ennis, John M.; Ennis, Daniel M.

    2014-01-01

    /preference responses or ties in choice experiments. Food Quality and Preference, 23, 13–17) noted that this proportion can depend on the product category, have proposed that the expected proportion of preference responses within a given category be called an identicality norm, and have argued that knowledge...... of such norms is valuable for more complete interpretation of 2-Alternative Choice (2-AC) data. For instance, these norms can be used to indicate consumer segmentation even with non-replicated data. In this paper, we show that the statistical test suggested by Ennis and Ennis (2012a) behaves poorly and has too...... when ingredient changes are considered for cost-reduction or health initiative purposes....

  12. AN UNSUPERVISED CHANGE DETECTION BASED ON TEST STATISTIC AND KI FROM MULTI-TEMPORAL AND FULL POLARIMETRIC SAR IMAGES

    Directory of Open Access Journals (Sweden)

    J. Q. Zhao

    2016-06-01

    Full Text Available Accurate and timely change detection of Earth’s surface features is extremely important for understanding relationships and interactions between people and natural phenomena. Many traditional methods of change detection only use a part of polarization information and the supervised threshold selection. Those methods are insufficiency and time-costing. In this paper, we present a novel unsupervised change-detection method based on quad-polarimetric SAR data and automatic threshold selection to solve the problem of change detection. First, speckle noise is removed for the two registered SAR images. Second, the similarity measure is calculated by the test statistic, and automatic threshold selection of KI is introduced to obtain the change map. The efficiency of the proposed method is demonstrated by the quad-pol SAR images acquired by Radarsat-2 over Wuhan of China.

  13. Particle-particle correlations and lifetimes of composite nuclei: New tests for the evaporation model and for statistical equilibration

    International Nuclear Information System (INIS)

    DeYoung, P.A.; Gelderloos, C.J.; Kortering, D.; Sarafa, J.; Zienert, K.; Gordon, M.S.; Fineman, B.J.; Gilfoyle, G.P.; Lu, X.; McGrath, R.L.; de Castro Rizzo, D.M.; Alexander, J.M.; Auger, G.; Kox, S.; Vaz, L.C.; Beck, C.; Henderson, D.J.; Kovar, D.G.; Vineyard, M.F.; Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794; Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794; Argonne National Laboratory, Argonne, Illinois 60439)

    1990-01-01

    We present data for small-angle particle-particle correlations from the reactions 80, 140, 215, and 250 MeV 16 O+ 27 Al→p-p or p-d. The main features of these data are anticorrelations for small relative momenta (≤25 MeV/c) that strengthen with increasing bombarding energy. Statistical model calculations have been performed to predict the mean lifetimes for each step of evaporative decay, and then simulate the trajectories of the particle pairs and the resulting particle correlations. This simulation accounts very well for the trends of the data and can provide an important new test for the hypothesis of equilibration on which the model is built

  14. Does bisphenol A induce superfeminization in Marisa cornuarietis? Part II: toxicity test results and requirements for statistical power analyses.

    Science.gov (United States)

    Forbes, Valery E; Aufderheide, John; Warbritton, Ryan; van der Hoeven, Nelly; Caspers, Norbert

    2007-03-01

    This study presents results of the effects of bisphenol A (BPA) on adult egg production, egg hatchability, egg development rates and juvenile growth rates in the freshwater gastropod, Marisa cornuarietis. We observed no adult mortality, substantial inter-snail variability in reproductive output, and no effects of BPA on reproduction during 12 weeks of exposure to 0, 0.1, 1.0, 16, 160 or 640 microg/L BPA. We observed no effects of BPA on egg hatchability or timing of egg hatching. Juveniles showed good growth in the control and all treatments, and there were no significant effects of BPA on this endpoint. Our results do not support previous claims of enhanced reproduction in Marisa cornuarietis in response to exposure to BPA. Statistical power analysis indicated high levels of inter-snail variability in the measured endpoints and highlighted the need for sufficient replication when testing treatment effects on reproduction in M. cornuarietis with adequate power.

  15. Model test study of evaporation mechanism of sand under constant atmospheric condition

    OpenAIRE

    CUI, Yu Jun; DING, Wenqi; SONG, Weikang

    2014-01-01

    The evaporation mechanism of Fontainebleau sand using a large-scale model chamber is studied. First, the evaporation test on a layer of water above sand surface is performed under various atmospheric conditions, validating the performance of the chamber and the calculation method of actual evaporation rate by comparing the calculated and measured cumulative evaporations. Second,the evaporation test on sand without water layer is conducted under constant atmospheric condition. Both the evoluti...

  16. Note: An online testing method for lifetime projection of high power light-emitting diode under accelerated reliability test.

    Science.gov (United States)

    Chen, Qi; Chen, Quan; Luo, Xiaobing

    2014-09-01

    In recent years, due to the fast development of high power light-emitting diode (LED), its lifetime prediction and assessment have become a crucial issue. Although the in situ measurement has been widely used for reliability testing in laser diode community, it has not been applied commonly in LED community. In this paper, an online testing method for LED life projection under accelerated reliability test was proposed and the prototype was built. The optical parametric data were collected. The systematic error and the measuring uncertainty were calculated to be within 0.2% and within 2%, respectively. With this online testing method, experimental data can be acquired continuously and sufficient amount of data can be gathered. Thus, the projection fitting accuracy can be improved (r(2) = 0.954) and testing duration can be shortened.

  17. The Use of Statistical Process Control-Charts for Person-Fit Analysis on Computerized Adaptive Testing. LSAC Research Report Series.

    Science.gov (United States)

    Meijer, Rob R.; van Krimpen-Stoop, Edith M. L. A.

    In this study a cumulative-sum (CUSUM) procedure from the theory of Statistical Process Control was modified and applied in the context of person-fit analysis in a computerized adaptive testing (CAT) environment. Six person-fit statistics were proposed using the CUSUM procedure, and three of them could be used to investigate the CAT in online test…

  18. A Correlated Study of the Response of a Satellite to Acoustic Radiation Using Statistical Energy Analysis and Acoustic Test Data

    International Nuclear Information System (INIS)

    CAP, JEROME S.; TRACEY, BRIAN

    1999-01-01

    Aerospace payloads, such as satellites, are subjected to vibroacoustic excitation during launch. Sandia's MTI satellite has recently been certified to this environment using a combination of base input random vibration and reverberant acoustic noise. The initial choices for the acoustic and random vibration test specifications were obtained from the launch vehicle Interface Control Document (ICD). In order to tailor the random vibration levels for the laboratory certification testing, it was necessary to determine whether vibration energy was flowing across the launch vehicle interface from the satellite to the launch vehicle or the other direction. For frequencies below 120 Hz this issue was addressed using response limiting techniques based on results from the Coupled Loads Analysis (CLA). However, since the CLA Finite Element Analysis FEA model was only correlated for frequencies below 120 Hz, Statistical Energy Analysis (SEA) was considered to be a better choice for predicting the direction of the energy flow for frequencies above 120 Hz. The existing SEA model of the launch vehicle had been developed using the VibroAcoustic Payload Environment Prediction System (VAPEPS) computer code[1]. Therefore, the satellite would have to be modeled using VAPEPS as well. As is the case for any computational model, the confidence in its predictive capability increases if one can correlate a sample prediction against experimental data. Fortunately, Sandia had the ideal data set for correlating an SEA model of the MTI satellite--the measured response of a realistic assembly to a reverberant acoustic test that was performed during MTI's qualification test series. The first part of this paper will briefly describe the VAPEPS modeling effort and present the results of the correlation study for the VAPEPS model. The second part of this paper will present the results from a study that used a commercial SEA software package[2] to study the effects of in-plane modes and to evaluate

  19. Test method research on weakening interface strength of steel - concrete under cyclic loading

    Science.gov (United States)

    Liu, Ming-wei; Zhang, Fang-hua; Su, Guang-quan

    2018-02-01

    The mechanical properties of steel - concrete interface under cyclic loading are the key factors affecting the rule of horizontal load transfer, the calculation of bearing capacity and cumulative horizontal deformation. Cyclic shear test is an effective method to study the strength reduction of steel - concrete interface. A test system composed of large repeated direct shear test instrument, hydraulic servo system, data acquisition system, test control software system and so on is independently designed, and a set of test method, including the specimen preparation, the instrument preparation, the loading method and so on, is put forward. By listing a set of test results, the validity of the test method is verified. The test system and the test method based on it provide a reference for the experimental study on mechanical properties of steel - concrete interface.

  20. Collaborative testing for key-term definitions under representative conditions: Efficiency costs and no learning benefits.

    Science.gov (United States)

    Wissman, Kathryn T; Rawson, Katherine A

    2018-01-01

    Students are expected to learn key-term definitions across many different grade levels and academic disciplines. Thus, investigating ways to promote understanding of key-term definitions is of critical importance for applied purposes. A recent survey showed that learners report engaging in collaborative practice testing when learning key-term definitions, with outcomes also shedding light on the way in which learners report engaging in collaborative testing in real-world contexts (Wissman & Rawson, 2016, Memory, 24, 223-239). However, no research has directly explored the effectiveness of engaging in collaborative testing under representative conditions. Accordingly, the current research evaluates the costs (with respect to efficiency) and the benefits (with respect to learning) of collaborative testing for key-term definitions under representative conditions. In three experiments (ns = 94, 74, 95), learners individually studied key-term definitions and then completed retrieval practice, which occurred either individually or collaboratively (in dyads). Two days later, all learners completed a final individual test. Results from Experiments 1-2 showed a cost (with respect to efficiency) and no benefit (with respect to learning) of engaging in collaborative testing for key-term definitions. Experiment 3 evaluated a theoretical explanation for why collaborative benefits do not emerge under representative conditions. Collectively, outcomes indicate that collaborative testing versus individual testing is less effective and less efficient when learning key-term definitions under representative conditions.

  1. Extensible Synthetic File Servers? or: Structuring the Glue between Tester and System Under Test

    NARCIS (Netherlands)

    Belinfante, Axel; Mullender, Sape J.; Collyer, G.

    2007-01-01

    We discuss a few simple scenarios of how we can design and develop a compositional synthetic ��?le server that gives access to external processes – in particular, in the context of testing, gives access to the system under test – such that certain parts of said synthethic ��?le server can be

  2. Steady-State PMU Compliance Test under C37.118.1a-2014

    DEFF Research Database (Denmark)

    Ghiga, Radu; Wu, Qiuwei; Martin, Kenneth E.

    2016-01-01

    This paper presents a flexible testing method and the steady-state compliance of PMUs under the C37.118.1a amendment. The work is focused on the changes made to the standard for the harmonic rejection and out-of-band interference tests for which the ROCOF Error limits have been suspended. The paper...

  3. An Efficient Stepwise Statistical Test to Identify Multiple Linked Human Genetic Variants Associated with Specific Phenotypic Traits.

    Directory of Open Access Journals (Sweden)

    Iksoo Huh

    Full Text Available Recent advances in genotyping methodologies have allowed genome-wide association studies (GWAS to accurately identify genetic variants that associate with common or pathological complex traits. Although most GWAS have focused on associations with single genetic variants, joint identification of multiple genetic variants, and how they interact, is essential for understanding the genetic architecture of complex phenotypic traits. Here, we propose an efficient stepwise method based on the Cochran-Mantel-Haenszel test (for stratified categorical data to identify causal joint multiple genetic variants in GWAS. This method combines the CMH statistic with a stepwise procedure to detect multiple genetic variants associated with specific categorical traits, using a series of associated I × J contingency tables and a null hypothesis of no phenotype association. Through a new stratification scheme based on the sum of minor allele count criteria, we make the method more feasible for GWAS data having sample sizes of several thousands. We also examine the properties of the proposed stepwise method via simulation studies, and show that the stepwise CMH test performs better than other existing methods (e.g., logistic regression and detection of associations by Markov blanket for identifying multiple genetic variants. Finally, we apply the proposed approach to two genomic sequencing datasets to detect linked genetic variants associated with bipolar disorder and obesity, respectively.

  4. The quantitative LOD score: test statistic and sample size for exclusion and linkage of quantitative traits in human sibships.

    Science.gov (United States)

    Page, G P; Amos, C I; Boerwinkle, E

    1998-04-01

    We present a test statistic, the quantitative LOD (QLOD) score, for the testing of both linkage and exclusion of quantitative-trait loci in randomly selected human sibships. As with the traditional LOD score, the boundary values of 3, for linkage, and -2, for exclusion, can be used for the QLOD score. We investigated the sample sizes required for inferring exclusion and linkage, for various combinations of linked genetic variance, total heritability, recombination distance, and sibship size, using fixed-size sampling. The sample sizes required for both linkage and exclusion were not qualitatively different and depended on the percentage of variance being linked or excluded and on the total genetic variance. Information regarding linkage and exclusion in sibships larger than size 2 increased as approximately all possible pairs n(n-1)/2 up to sibships of size 6. Increasing the recombination (theta) distance between the marker and the trait loci reduced empirically the power for both linkage and exclusion, as a function of approximately (1-2theta)4.

  5. Aspects of the statistical theory of stochastic magnetic fields: test particle transport and turbulent collisionless tearing mode

    International Nuclear Information System (INIS)

    Kleva, R.G.

    1980-01-01

    The first part of this work is concerned with test particle transport in a stochastic magnetic field. In the absence of collisions, the test particle self-diffusion coefficient is given by D = D/sub m/ V (in the zero gyroradius limit), where D/sub m/ is the magnetic diffusion coefficient due to a given spectrum of magnetic fluctuations and V is the particle velocity along a field line. The effect of collisions, either classical or turbulent, on this result is considered. The second part of this work is concerned with the evolution of the collisionless tearing mode in the presence of a stochastic magnetic field. A statistical closure approximation, obtained from the DIA by neglecting a mode-coupling term, is used to derive a nonlinear dispersion relation. For L 0 < L/sub K/ the dominant nonlinear effect is shown to be a turbulent broadening of the perturbed current layer. Saturation occurs when the perturbed current layer broadens to the point where Δ' = 0, where Δ' is the jump in the logarithmic derivative of the vector potential across the perturbed current layer

  6. Comparison of the release of constituents from granular materials under batch and column testing.

    Science.gov (United States)

    Lopez Meza, Sarynna; Garrabrants, Andrew C; van der Sloot, Hans; Kosson, David S

    2008-01-01

    Column leaching testing can be considered a better basis for assessing field impact data than any other available batch test method and thus provides a fundamental basis from which to estimate constituent release under a variety of field conditions. However, column testing is time-intensive compared to the more simplified batch testing, and may not always be a viable option when making decisions for material reuse. Batch tests are used most frequently as a simple tool for compliance or quality control reasons. Therefore, it is important to compare the release that occurs under batch and column testing, and establish conservative interpretation protocols for extrapolation from batch data when column data are not available. Five different materials (concrete, construction debris, aluminum recycling residue, coal fly ash and bottom ash) were evaluated via batch and column testing, including different column flow regimes (continuously saturated and intermittent unsaturated flow). Constituent release data from batch and column tests were compared. Results showed no significant difference between the column flow regimes when constituent release data from batch and column tests were compared. In most cases batch and column testing agreed when presented in the form of cumulative release. For arsenic in carbonated materials, however, batch testing underestimates the column constituent release for most LS ratios and also on a cumulative basis. For cases when As is a constituent of concern, column testing may be required.

  7. Calculation of Tajima's D and other neutrality test statistics from low depth next-generation sequencing data

    DEFF Research Database (Denmark)

    Korneliussen, Thorfinn Sand; Moltke, Ida; Albrechtsen, Anders

    2013-01-01

    A number of different statistics are used for detecting natural selection using DNA sequencing data, including statistics that are summaries of the frequency spectrum, such as Tajima's D. These statistics are now often being applied in the analysis of Next Generation Sequencing (NGS) data. Howeve......, estimates of frequency spectra from NGS data are strongly affected by low sequencing coverage; the inherent technology dependent variation in sequencing depth causes systematic differences in the value of the statistic among genomic regions....

  8. Tests of qualification of national components of nuclear power plants under design basis accident

    International Nuclear Information System (INIS)

    Mesquita, A.Z.

    1990-01-01

    With the purpose of qualifying national components of nuclear power plants, whose working must be maintained during and after an accident, the Thermohydraulic Division of CDTN have done tests to check the equipment stability, under Design Basis Accident conditions. Until this moment, the following components were tested: electrical junction boxes (connectors); coating systems for wall, inside cover and steel containment; hydraulics components of personnel and equipment airlock. This work describes the test instalation, the tests performed and its results. The components tested, in a general way, fulfil the specified requirements. (author) [pt

  9. Statistical energy as a tool for binning-free, multivariate goodness-of-fit tests, two-sample comparison and unfolding

    International Nuclear Information System (INIS)

    Aslan, B.; Zech, G.

    2005-01-01

    We introduce the novel concept of statistical energy as a statistical tool. We define statistical energy of statistical distributions in a similar way as for electric charge distributions. Charges of opposite sign are in a state of minimum energy if they are equally distributed. This property is used to check whether two samples belong to the same parent distribution, to define goodness-of-fit tests and to unfold distributions distorted by measurement. The approach is binning-free and especially powerful in multidimensional applications

  10. Seed vigour tests for predicting field emergence of maize under severe conditions

    OpenAIRE

    García de Yzaguirre, Álvaro; Lasa Dolhagaray, José Manuel

    1989-01-01

    [EN] With 40 to 50 different seed vigour tests available, appropiate procedures for choosing the best single test or combination the best predictors of seedling emergence of maize (Zea Mays L.) under severe conditions. Thirteen vigour tests and various field emergence trials were performed on six inbred lines and two commercial hybrids. The best single predictors of field emergence were identified by calculating simple correlation coefficients. The calculation of the geometric mean of the res...

  11. Stability of selected volatile contact allergens in different patch test chambers under different storage conditions

    DEFF Research Database (Denmark)

    Mose, Kristian Fredløv; Andersen, Klaus Ejner; Christensen, Lars Porskjaer

    2012-01-01

    Background. Patch test preparations of volatile substances may evaporate during storage, thereby giving rise to reduced patch test concentrations. Objectives. To investigate the stability of selected acrylates/methacrylates and fragrance allergens in three different test chambers under different...... both storage conditions, whereas MMA and 2-HPA required cool storage for maintenance of the limit. Conclusion. The Van der Bend® transport container was the best device for storage of samples of volatile contact allergens....

  12. Dynamic Brazilian Test of Rock Under Intermediate Strain Rate: Pendulum Hammer-Driven SHPB Test and Numerical Simulation

    Science.gov (United States)

    Zhu, W. C.; Niu, L. L.; Li, S. H.; Xu, Z. H.

    2015-09-01

    The tensile strength of rock subjected to dynamic loading constitutes many engineering applications such as rock drilling and blasting. The dynamic Brazilian test of rock specimens was conducted with the split Hopkinson pressure bar (SHPB) driven by pendulum hammer, in order to determine the indirect tensile strength of rock under an intermediate strain rate ranging from 5.2 to 12.9 s-1, which is achieved when the incident bar is impacted by pendulum hammer with different velocities. The incident wave excited by pendulum hammer is triangular in shape, featuring a long rising time, and it is considered to be helpful for achieving a constant strain rate in the rock specimen. The dynamic indirect tensile strength of rock increases with strain rate. Then, the numerical simulator RFPA-Dynamics, a well-recognized software for simulating the rock failure under dynamic loading, is validated by reproducing the Brazilian test of rock when the incident stress wave retrieved at the incident bar is input as the boundary condition, and then it is employed to study the Brazilian test of rock under the higher strain rate. Based on the numerical simulation, the strain-rate dependency of tensile strength and failure pattern of the Brazilian disc specimen under the intermediate strain rate are numerically simulated, and the associated failure mechanism is clarified. It is deemed that the material heterogeneity should be a reason for the strain-rate dependency of rock.

  13. Materials interactions test methods to measure radionuclide release from waste forms under repository-relevant conditions

    International Nuclear Information System (INIS)

    Strickert, R.G.; Erikson, R.L.; Shade, J.W.

    1984-10-01

    At the request of the Basalt Waste Isolation Project, the Materials Characterization Center has collected and developed a set of procedures into a waste form compliance test method (MCC-14.4). The purpose of the test is to measure the steady-state concentrations of specified radionuclides in solutions contacting a waste form material. The test method uses a crushed waste form and basalt material suspended in a synthetic basalt groundwater and agitated for up to three months at 150 0 C under anoxic conditions. Elemental and radioisotopic analyses are made on filtered and unfiltered aliquots of the solution. Replicate experiments are performed and simultaneous tests are conducted with an approved test material (ATM) to help ensure precise and reliable data for the actual waste form material. Various features of the test method, equipment, and test conditions are reviewed. Experimental testing using actinide-doped borosilicate glasses are also discussed. 9 references, 2 tables

  14. Diurnal and Seasonal Statistical Characteristics of Well-formed Plasma Depletion and Enhancement Plumes under Quiet Solar Conditions

    Science.gov (United States)

    Haaser, R. A.

    2011-12-01

    The Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamics Investigation (CINDI) aboard the Communication/ Navigation Outage Forecasting System (C/NOFS) satellite, is used to measure in situ ion densities and drifts at altitudes between 400 and 550 km during the nighttime hours from 2100 to 300 local time. A new approach to detecting and classifying well-formed ionospheric plasma depletion and enhancement plumes (bubbles and blobs) of scale sizes between 50 and 500 km is used to develop geophysical statistics for the summer, winter and equinox seasons of the quiet solar conditions during 2009 and 2010. Some diurnal and seasonal geomagnetic distribution characteristics confirm previous work on irregularities and scintillations, while others reveal new behaviors that require additional observations and modeling to promote full understanding.

  15. Statistical Study on Respiratory Stability Through RPM Signal Analysis according to Patient Position Under Radiation Therapy and Device

    International Nuclear Information System (INIS)

    Park, Myung Hwan; Seo, Jeong Min; Choi, Byeong Gi; Shin, Eun Hyeok; Song, Gi Won

    2011-01-01

    This study statistically analyzed the difference of the stability of maintaining a respiratory period shown according to position and use of a device to search the tendency and usefulness of a device. The study obtained respiratory signals which maintained a respiratory period for 20 minutes each supine and prone position for 11 subjects. The study obtained respiratory signals in a state of using a belly board for 7 patients in a bad condition of a respiratory period in a prone position to analyze a change in respiration and the stability before and after the use of a device. The supine part showed 54.5%, better than the prone part of 36.4% in a case that the stability for maintaining a respiratory period was in a good condition as a fixed respiratory period was well maintained according to the position. 6 patients (85%) showed a maintenance pattern of a respiratory period significantly different before the use and 4 patients showed a significantly good change in the stability for maintaining a respiratory period as a result that belly boards were used for 7 patients that the maintenance of a respiratory period was not in a good condition on a prone position. It seemed that this study could contribute to the maintenance of respiratory period and of respiratory stability as the optimal position for maintenance of respiration and the use of a device such as a belly board were decided through statistic analysis of respiratory signals and its application even if patient position and use of device were decided by the beam arrangement a treatment part of a patient, location of a target, and an expected plan.

  16. Standard Test Method for Testing Polymeric Seal Materials for Geothermal and/or High Temperature Service Under Sealing Stress

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1985-01-01

    1.1 This test method covers the initial evaluation of (screening) polymeric materials for seals under static sealing stress and at elevated temperatures. 1.2 This test method applies to geothermal service only if used in conjunction with Test Method E 1068. 1.3 The test fluid is distilled water. 1.4 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  17. Testing earthquake prediction algorithms: Statistically significant advance prediction of the largest earthquakes in the Circum-Pacific, 1992-1997

    Science.gov (United States)

    Kossobokov, V.G.; Romashkova, L.L.; Keilis-Borok, V. I.; Healy, J.H.

    1999-01-01

    Algorithms M8 and MSc (i.e., the Mendocino Scenario) were used in a real-time intermediate-term research prediction of the strongest earthquakes in the Circum-Pacific seismic belt. Predictions are made by M8 first. Then, the areas of alarm are reduced by MSc at the cost that some earthquakes are missed in the second approximation of prediction. In 1992-1997, five earthquakes of magnitude 8 and above occurred in the test area: all of them were predicted by M8 and MSc identified correctly the locations of four of them. The space-time volume of the alarms is 36% and 18%, correspondingly, when estimated with a normalized product measure of empirical distribution of epicenters and uniform time. The statistical significance of the achieved results is beyond 99% both for M8 and MSc. For magnitude 7.5 + , 10 out of 19 earthquakes were predicted by M8 in 40% and five were predicted by M8-MSc in 13% of the total volume considered. This implies a significance level of 81% for M8 and 92% for M8-MSc. The lower significance levels might result from a global change in seismic regime in 1993-1996, when the rate of the largest events has doubled and all of them become exclusively normal or reversed faults. The predictions are fully reproducible; the algorithms M8 and MSc in complete formal definitions were published before we started our experiment [Keilis-Borok, V.I., Kossobokov, V.G., 1990. Premonitory activation of seismic flow: Algorithm M8, Phys. Earth and Planet. Inter. 61, 73-83; Kossobokov, V.G., Keilis-Borok, V.I., Smith, S.W., 1990. Localization of intermediate-term earthquake prediction, J. Geophys. Res., 95, 19763-19772; Healy, J.H., Kossobokov, V.G., Dewey, J.W., 1992. A test to evaluate the earthquake prediction algorithm, M8. U.S. Geol. Surv. OFR 92-401]. M8 is available from the IASPEI Software Library [Healy, J.H., Keilis-Borok, V.I., Lee, W.H.K. (Eds.), 1997. Algorithms for Earthquake Statistics and Prediction, Vol. 6. IASPEI Software Library]. ?? 1999 Elsevier

  18. Reliability data collection on IC and VLSI devices tested under accelerated life conditions

    International Nuclear Information System (INIS)

    Barry, D.M.; Meniconi, M.

    1986-01-01

    As part of a more general investigation into the reliability and failure causes of semiconductor devices, statistical samples of integrated circuit devices (LM741C) and dynamic random access memory devices (TMS4116) were tested destructively to failure using elevated temperature as the accelerating stress. The devices were operated during the life test and the failure data generated were collected automatically using a multiple question-and-answer program and a process control computer. The failure data were modelled from the lognormal, inverse Gaussian and Weibull distribution using an Arrhenius reaction rate model. The failed devices were later decapsulated for failure cause determination. (orig./DG)

  19. Standard Test Method for Electrical Performance of Concentrator Terrestrial Photovoltaic Modules and Systems Under Natural Sunlight

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This test method covers the determination of the electrical performance of photovoltaic concentrator modules and systems under natural sunlight using a normal incidence pyrheliometer. 1.2 The test method is limited to module assemblies and systems where the geometric concentration ratio specified by the manufacturer is greater than 5. 1.3 This test method applies to concentrators that use passive cooling where the cell temperature is related to the air temperature. 1.4 Measurements under a variety of conditions are allowed; results are reported under a select set of concentrator reporting conditions to facilitate comparison of results. 1.5 This test method applies only to concentrator terrestrial modules and systems. 1.6 This test method assumes that the module or system electrical performance characteristics do not change during the period of test. 1.7 The performance rating determined by this test method applies only at the period of the test, and implies no past or future performance level. 1.8...

  20. Endurance of lead-free assembly under board level drop test and thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Xia Yanghua [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)], E-mail: xia_yanghua@hotmail.com; Xie Xiaoming [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2008-06-12

    The reliability of lead-free electronic assemblies under board level drop test and thermal cycling was investigated. TSOP (thin small outline package) devices with FeNi leads were reflow soldered on FR4 PCB (printed circuit board) with Sn3.0Ag0.5Cu (wt%) solder. The effects of different PCB finishes (organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG)) on the reliability performance were studied. The results show that the assemblies with ENIG finishes reveal better reliability performance than its OSP counterparts under drop test, however, the OSP samples outperform those with ENIG finishes under thermal cycling. The failure mechanism is different under these two test conditions: the solder joints fracture into the intermetallic compounds (IMCs) layer under drop test, and cracks initiate in the bulk solder under thermal cycling. The surface finishes have an effect on the failure mode. The propagation of crack in the ENIG case is along the device/solder interface, while in the case of OSP, the crack extends parallel to the solder/PCB interface.