Similar tests and the standardized log likelihood ratio statistic
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...
Generalized Correlation Coefficient Based on Log Likelihood Ratio Test Statistic
Liu Hsiang-Chuan
2016-01-01
Full Text Available In this paper, I point out that both Joe’s and Ding’s strength statistics can only be used for testing the pair-wise independence, and I propose a novel G-square based strength statistic, called Liu’s generalized correlation coefficient, it can be used to detect and compare the strength of not only the pair-wise independence but also the mutual independence of any multivariate variables. Furthermore, I proved that only Liu’s generalized correlation coefficient is strictly increasing on its number of variables, it is more sensitive and useful than Cramer’s V coefficient, in other words, Liu generalized correlation coefficient is not only the G-square based strength statistic, but also an improved statistic for detecting and comparing the strengths of deferent associations of any two or more sets of multivariate variables, moreover, this new strength statistic can also be tested by G2.
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, s......, 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....
Application of a generalized likelihood ratio test statistic to MAGIC data
Klepser, S; 10.1063/1.4772359
2012-01-01
The commonly used detection test statistic for Cherenkov telescope data is Li & Ma (1983), Eq. 17. It evaluates the compatibility of event counts in an on-source region with those in a representative off-region. It does not exploit the typically known gamma-ray point spread function (PSF) of a system, and in practice its application requires either assumptions on the symmetry of the acceptance across the field of view, orMonte Carlo simulations.MAGIC has an azimuth-dependent, asymmetric acceptance which required a careful review of detection statistics. Besides an adapted Li & Ma based technique, the recently presented generalized LRT statistic of [1] is now in use. It is more flexible, more sensitive and less systematics-affected, because it is highly customized for multi-pointing Cherenkov telescope data with a known PSF. We present the application of this new method to archival MAGIC data and compare it to the other, Li&Ma-based method.
Weber, Benjamin; Lee, Sau L; Lionberger, Robert; Li, Bing V; Tsong, Yi; Hochhaus, Guenther
2013-04-01
Demonstration of equivalence in aerodynamic particle size distribution (APSD) is one key component for establishing bioequivalence of orally inhaled drug products. We previously proposed a modified version of the Chi-square ratio statistic (mCSRS) for APSD equivalence testing and demonstrated that the median of the distribution of the mCSRS (MmCSRS) is a robust metric when test (T) and reference (R) cascade impactor (CI) profiles are identical. Here, we systematically evaluate the behavior of the MmCSRS when T and R CI profiles differ from each other in their mean deposition and variability on a single and multiple sites. All CI profiles were generated by Monte-Carlo simulations based upon modified actual CI data. Twenty thousand sets of 30 T and 30 R CI profiles were simulated for each scenario, and the behavior of the MmCSRS was correlated to metrics that characterize the difference between T and R product in mean deposition and variability. The two key findings were, first, that the MmCSRS is more sensitive to difference between T and R CI profiles on high deposition sites, and second, that a cut-off value for APSD equivalence testing based on the MmCSRS needs to be scaled on the variability of the R product. The former is considered as beneficial for equivalence testing of CI profiles as it decreases the likelihood of failing identical CI profiles by chance, in part, due to increasing analytical variability associated with lower deposition sites. The latter is expected to be important for consistently being able to discriminate equivalent from inequivalent CI profiles.
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.
1981-09-01
Statistics, Carnegie-Mellon University. **At present with the Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio. #.,p- edfor puL lic...recurrence relation 3J B. - Z kak8" k ’ o = 1 (2.7) J -O k =l k . We use the following notations as defined in James (1964). The complex multivariate...gamma functions F’ (a)p and r P(a, K ) are given by (a) p(p-l)/2 P (a) = Tp ) r(a-i+l). (2.8) p i=l pa <) p(p-l)/2 Pr (a, K ) = n(a-i+l+ki) (2.9) i=l where
Weber, Benjamin; Hochhaus, Guenther; Adams, Wallace; Lionberger, Robert; Li, Bing; Tsong, Yi; Lee, Sau L
2013-01-01
Demonstration of equivalence in aerodynamic particle size distribution (APSD; e.g., by comparing cascade impactor (CI) profiles) constitutes one of key in vitro tests for supporting bioequivalence between test (T) and reference (R) orally inhaled drug products (OIDPs). A chi-square ratio statistic (CSRS) was previously proposed for equivalence testing of CI profiles. However, it was reported that the CSRS could not consistently discriminate between equivalent and inequivalent CI profiles. The objective of the overall project was to develop a robust and sensitive methodology for assessing equivalence of APSD profiles of T and R OIDPs. We propose here a modified version of the CSRS (mCSRS) and evaluated systematically its behavior when T and R CI profiles were identical. Different scenarios comprising CI profiles with different number of deposition sites and shapes were generated by Monte-Carlo simulation. For each scenario, the mCSRS was applied to 20,000 independent sets of 30 T and 30 R CI profiles that were identical. Different metrics (including mean and median) of the distribution of 900 mCSRSs (30 T × 30 R) were then evaluated for their suitability as a test statistic (i.e., independent of the number of sites and shape of the CI profile) for APSD equivalence testing. The median of the distribution of 900 mCSRSs (MmCSRS) was one regardless of the number of sites and shape of the CI profile. Hence, the MmCSRS is a robust metric for CI profile equivalence testing when T and R CI profiles are identical and potentially useful for APSD equivalence testing.
Ramos Verri, Fellippo; Santiago Junior, Joel Ferreira; de Faria Almeida, Daniel Augusto; de Oliveira, Guilherme Bérgamo Brandão; de Souza Batista, Victor Eduardo; Marques Honório, Heitor; Noritomi, Pedro Yoshito; Pellizzer, Eduardo Piza
2015-01-02
The study of short implants is relevant to the biomechanics of dental implants, and research on crown increase has implications for the daily clinic. The aim of this study was to analyze the biomechanical interactions of a singular implant-supported prosthesis of different crown heights under vertical and oblique force, using the 3-D finite element method. Six 3-D models were designed with Invesalius 3.0, Rhinoceros 3D 4.0, and Solidworks 2010 software. Each model was constructed with a mandibular segment of bone block, including an implant supporting a screwed metal-ceramic crown. The crown height was set at 10, 12.5, and 15 mm. The applied force was 200 N (axial) and 100 N (oblique). We performed an ANOVA statistical test and Tukey tests; p0.05) under axial load. However, crown heights of 12.5 and 15 mm caused statistically significant damage to the stress distribution of screws and to the cortical bone (p<0.001) under oblique load. High crown to implant (C/I) ratio harmed microstrain distribution on bone tissue under axial and oblique loads (p<0.001). Crown increase was a possible deleterious factor to the screws and to the different regions of bone tissue.
Testing statistical hypotheses
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...
Statistical Test for Bivariate Uniformity
Zhenmin Chen
2014-01-01
Full Text Available The purpose of the multidimension uniformity test is to check whether the underlying probability distribution of a multidimensional population differs from the multidimensional uniform distribution. The multidimensional uniformity test has applications in various fields such as biology, astronomy, and computer science. Such a test, however, has received less attention in the literature compared with the univariate case. A new test statistic for checking multidimensional uniformity is proposed in this paper. Some important properties of the proposed test statistic are discussed. As a special case, the bivariate statistic test is discussed in detail in this paper. The Monte Carlo simulation is used to compare the power of the newly proposed test with the distance-to-boundary test, which is a recently published statistical test for multidimensional uniformity. It has been shown that the test proposed in this paper is more powerful than the distance-to-boundary test in some cases.
Explorations in Statistics: The Analysis of Ratios and Normalized Data
Curran-Everett, Douglas
2013-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This ninth installment of "Explorations in Statistics" explores the analysis of ratios and normalized--or standardized--data. As researchers, we compute a ratio--a numerator divided by a denominator--to compute a…
Testing statistical hypotheses of equivalence
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
Kaufman Jay S
2008-07-01
Full Text Available Abstract In 2004, Garcia-Berthou and Alcaraz published "Incongruence between test statistics and P values in medical papers," a critique of statistical errors that received a tremendous amount of attention. One of their observations was that the final reported digit of p-values in articles published in the journal Nature departed substantially from the uniform distribution that they suggested should be expected. In 2006, Jeng critiqued that critique, observing that the statistical analysis of those terminal digits had been based on comparing the actual distribution to a uniform continuous distribution, when digits obviously are discretely distributed. Jeng corrected the calculation and reported statistics that did not so clearly support the claim of a digit preference. However delightful it may be to read a critique of statistical errors in a critique of statistical errors, we nevertheless found several aspects of the whole exchange to be quite troubling, prompting our own meta-critique of the analysis. The previous discussion emphasized statistical significance testing. But there are various reasons to expect departure from the uniform distribution in terminal digits of p-values, so that simply rejecting the null hypothesis is not terribly informative. Much more importantly, Jeng found that the original p-value of 0.043 should have been 0.086, and suggested this represented an important difference because it was on the other side of 0.05. Among the most widely reiterated (though often ignored tenets of modern quantitative research methods is that we should not treat statistical significance as a bright line test of whether we have observed a phenomenon. Moreover, it sends the wrong message about the role of statistics to suggest that a result should be dismissed because of limited statistical precision when it is so easy to gather more data. In response to these limitations, we gathered more data to improve the statistical precision, and
Omar Chavez
2016-07-01
Full Text Available A method to improve the detection of seismo-magnetic signals is presented herein. Eight events registered for periods of 24 hours with seismic activity were analyzed and compared with non-seismic periods of the same duration. The distance between the earthquakes (EQs and the ultra-low frequency detector is of ρ = (1.8 100.45M, where M is the magnitude of the EQ reported by the Seismological National Service of Mexico, in a period of three years. An improved fast Fourier transform analysis in the form of the ratio of the vertical magnetic field component to the horizontal one (Q = Bz/Bx has been developed. There are important differences between the frequencies obtained during the days of seismic activity compared with those with no seismic activity.
SAW, J.G.
THIS VOLUME DEALS WITH THE BIVARIATE NORMAL DISTRIBUTION. THE AUTHOR MAKES A DISTINCTION BETWEEN DISTRIBUTION AND DENSITY FROM WHICH HE DEVELOPS THE CONSEQUENCES OF THIS DISTINCTION FOR HYPOTHESIS TESTING. OTHER ENTRIES IN THIS SERIES ARE ED 003 044 AND ED 003 045. (JK)
Monotonicity of chi-square test statistics
Ryu, Keunkwan
2003-01-01
This paper establishes monotonicity of the chi-square test statistic. As the more efficient parameter estimator is plugged into the test statistic, the degrees of freedom of the resulting chi-square test statistic monotonically increase.
Statistical tests to compare motif count exceptionalities
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.
The Laplace Likelihood Ratio Test for Heteroscedasticity
J. Martin van Zyl
2011-01-01
Full Text Available It is shown that the likelihood ratio test for heteroscedasticity, assuming the Laplace distribution, gives good results for Gaussian and fat-tailed data. The likelihood ratio test, assuming normality, is very sensitive to any deviation from normality, especially when the observations are from a distribution with fat tails. Such a likelihood test can also be used as a robust test for a constant variance in residuals or a time series if the data is partitioned into groups.
Stoica, Iuliana-Madalina; Babamoradi, Hamid; van den Berg, Frans
2017-01-01
•A statistical strategy combining fluorescence spectroscopy, multivariate analysis and Wilks’ ratio is proposed.•The method was tested both off-line and on-line having riboflavin as a (controlled) contaminant.•Wilks’ ratio signals unusual recordings based on shifts in variance and covariance stru...
Statistical hypothesis testing with SAS and R
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
2008-01-01
This paper investigates the asymptotic properties of the modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models with an unknown structural parameter. It is shown that the modified likelihood ratio statistic has χ22 null limiting distribution.
A Hybrid Joint Moment Ratio Test for Financial Time Series
Groenendijk, Patrick A.; Lucas, André; Vries, de Casper G.
1998-01-01
We advocate the use of absolute moment ratio statistics in conjunctionwith standard variance ratio statistics in order to disentangle lineardependence, non-linear dependence, and leptokurtosis in financial timeseries. Both statistics are computed for multiple return horizonssimultaneously, and the
A Hybrid Joint Moment Ratio Test for Financial Time Series
Groenendijk, Patrick A.; Lucas, André; Vries, de Casper G.
1998-01-01
We advocate the use of absolute moment ratio statistics in conjunctionwith standard variance ratio statistics in order to disentangle lineardependence, non-linear dependence, and leptokurtosis in financial timeseries. Both statistics are computed for multiple return horizonssimultaneously, and the r
Statistical equilibrium in cometary C2. II - Swan/Phillips band ratios
Swamy, K. S. K.; Odell, C. R.
1979-01-01
Statistical equilibrium calculations have been made for both the triplet and ground state singlets for C2 in comets, using the exchange rate as a free parameter. The predictions of the results are consistent with optical observations and may be tested definitively by accurate observations of the Phillips and Swan band ratios. Comparison with the one reported observation indicates compatibility with a low exchange rate and resonance fluorescence statistical equilibrium.
Polarimetric Segmentation Using Wishart Test Statistic
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....... The results show clearly an improved segmentation performance for the full polarimetric algorithm compared to single channel approaches....
Teaching Statistics in Language Testing Courses
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…
Teaching Statistics in Language Testing Courses
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…
Statistical Tests of Galactic Dynamo Theory
Chamandy, Luke; Shukurov, Anvar; Taylor, A. Russ
2016-12-01
Mean-field galactic dynamo theory is the leading theory to explain the prevalence of regular magnetic fields in spiral galaxies, but its systematic comparison with observations is still incomplete and fragmentary. Here we compare predictions of mean-field dynamo models to observational data on magnetic pitch angle and the strength of the mean magnetic field. We demonstrate that a standard {α }2{{Ω }} dynamo model produces pitch angles of the regular magnetic fields of nearby galaxies that are reasonably consistent with available data. The dynamo estimates of the magnetic field strength are generally within a factor of a few of the observational values. Reasonable agreement between theoretical and observed pitch angles generally requires the turbulent correlation time τ to be in the range of 10-20 {Myr}, in agreement with standard estimates. Moreover, good agreement also requires that the ratio of the ionized gas scale height to root-mean-square turbulent velocity increases with radius. Our results thus widen the possibilities to constrain interstellar medium parameters using observations of magnetic fields. This work is a step toward systematic statistical tests of galactic dynamo theory. Such studies are becoming more and more feasible as larger data sets are acquired using current and up-and-coming instruments.
Statistical analyses of plume composition and deposited radionuclide mixture ratios
Kraus, Terrence D.; Sallaberry, Cedric Jean-Marie; Eckert-Gallup, Aubrey Celia; Brito, Roxanne; Hunt, Brian D.; Osborn, Douglas.
2014-01-01
A proposed method is considered to classify the regions in the close neighborhood of selected measurements according to the ratio of two radionuclides measured from either a radioactive plume or a deposited radionuclide mixture. The subsequent associated locations are then considered in the area of interest with a representative ratio class. This method allows for a more comprehensive and meaningful understanding of the data sampled following a radiological incident.
SPSS for applied sciences basic statistical testing
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
无
2007-01-01
Suppose that several different imperfect instruments and one perfect instrument are independently used to measure some characteristics of a population. Thus, measurements of two or more sets of samples with varying accuracies are obtained. Statistical inference should be based on the pooled samples. In this article, the authors also assumes that all the imperfect instruments are unbiased. They consider the problem of combining this information to make statistical tests for parameters more relevant. They define the empirical likelihood ratio functions and obtain their asymptotic distributions in the presence of measurement error.
Statistical test of VEP waveform equality.
Young, Rockefeller S L; Kimura, Eiji
2010-04-01
The aim of the study was to describe a theory and method for inferring the statistical significance of a visually evoked cortical potential (VEP) recording. The statistical evaluation is predicated on the pre-stimulus VEP as estimates of the cortical potentials expected when the stimulus does not produce an effect, a mathematical transform to convert the voltages into standard deviations from zero, and a time-series approach for estimating the variability of between-session VEPs under the null hypothesis. Empirical and Monte Carlo analyses address issues concerned with testability, statistical validity, clinical feasibility, as well as limitations of the proposed method. We conclude that visual electrophysiological recordings can be evaluated as a statistical study of n = 1 subject using time-series analysis when confounding effects are adequately controlled. The statistical test can be performed on either a single VEP or the difference between pairs of VEPs.
Analysis of Preference Data Using Intermediate Test Statistic Abstract
PROF. O. E. OSUAGWU
2013-06-01
Jun 1, 2013 ... Intermediate statistic is a link between Friedman test statistic and the multinomial statistic. The statistic is ... The null hypothesis Ho .... [7] Taplin, R.H., The Statistical Analysis of Preference Data, Applied Statistics, No. 4, pp.
A Hybrid Joint Moment Ratio Test for Financial Time Series
P.A. Groenendijk (Patrick); A. Lucas (André); C.G. de Vries (Casper)
1998-01-01
textabstractWe advocate the use of absolute moment ratio statistics in conjunction with standard variance ratio statistics in order to disentangle linear dependence, non-linear dependence, and leptokurtosis in financial time series. Both statistics are computed for multiple return horizons
A Hybrid Joint Moment Ratio Test for Financial Time Series
P.A. Groenendijk (Patrick); A. Lucas (André); C.G. de Vries (Casper)
1998-01-01
textabstractWe advocate the use of absolute moment ratio statistics in conjunction with standard variance ratio statistics in order to disentangle linear dependence, non-linear dependence, and leptokurtosis in financial time series. Both statistics are computed for multiple return horizons simultane
Morphology and hardness ratio exploitation under limited statistics
Clapson, A -C; Nekrassov, D; Renaud, M
2008-01-01
Gamma-ray astronomy has produced for several years now sky maps for low photon statistics, non-negligible background and comparatively poor angular resolution. Quantifying the significance of spatial features remains difficult. Besides, spectrum extraction requires regions with large statistics while maps in energy bands allow only qualitative interpretation. The two main competing mechanisms in the VHE domain are the Inverse-Compton emission from accelerated electrons radiating through synchrotron in the X-ray domain and the interactions between accelerated hadrons and the surrounding medium, leading to the production and subsequent decay of Pi0 mesons. The spectrum of the VHE emission from leptons is predicted to steepen with increasing distance from the acceleration zone, owing to synchrotron losses (i.e. cooled population). It would remain approximately constant for hadrons. Ideally, spectro-imaging analysis would have the same spatial scale in the TeV and X-ray domains, to distinguish the local emission ...
A unitary test of the Ratios Conjecture
Goes, John; Miller, Steven J; Montague, David; Ninsuwan, Kesinee; Peckner, Ryan; Pham, Thuy
2009-01-01
The Ratios Conjecture of Conrey, Farmer and Zirnbauer predicts the answers to numerous questions in number theory, ranging from n-level densities and correlations to mollifiers to moments and vanishing at the central point. The conjecture gives a recipe to generate these answers, which are believed to be correct up to square-root cancelation. These predictions have been verified, for suitably restricted test functions, for the 1-level density of orthogonal and symplectic families of L-functions. In this paper we verify the conjecture's predictions for the unitary family of all Dirichlet $L$-functions with prime conductor; we show square-root agreement between prediction and number theory if the support of the Fourier transform of the test function is in (-1,1), and for support up to (-2,2) we show agreement up to a power savings in the family's cardinality. The interesting feature in this family (which has not surfaced in previous investigations) is determining what is and what is not a diagonal term in the R...
Total Protein and Albumin/Globulin Ratio Test
... products and services. Advertising & Sponsorship: Policy | Opportunities Total Protein and Albumin/Globulin (A/G) Ratio Share this ... Globulin Ratio; A/G Ratio Formal name: Total Protein; Albumin to Globulin Ratio Related tests: Albumin ; Liver ...
Statistical test theory for the behavioral sciences
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...
New Graphical Methods and Test Statistics for Testing Composite Normality
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.
A MODIFIED LIKELIHOOD RATIO TEST FOR HOMOGENEITY IN BIVARIATE NORMAL MIXTURES OF TWO SAMPLES
Qingzhu LEI; Yongsong QIN
2009-01-01
This paper investigates the asymptotic properties of a modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models of two samples. The asymptotic null distribution of the modified likelihood ratio statistic is found to be X~2_2, where X~2_2 is a chi-squared distribution with 2 degrees of freedom.
Bartroff, Jay
2011-01-01
A new approach to adaptive design of clinical trials is proposed in a general multiparameter exponential family setting, based on generalized likelihood ratio statistics and optimal sequential testing theory. These designs are easy to implement, maintain the prescribed Type I error probability, and are asymptotically efficient. Practical issues involved in clinical trials allowing mid-course adaptation and the large literature on this subject are discussed, and comparisons between the proposed and existing designs are presented in extensive simulation studies of their finite-sample performance, measured in terms of the expected sample size and power functions.
Conditional statistical inference with multistage testing designs.
Zwitser, Robert J; Maris, Gunter
2015-03-01
In this paper it is demonstrated how statistical inference from multistage test designs can be made based on the conditional likelihood. Special attention is given to parameter estimation, as well as the evaluation of model fit. Two reasons are provided why the fit of simple measurement models is expected to be better in adaptive designs, compared to linear designs: more parameters are available for the same number of observations; and undesirable response behavior, like slipping and guessing, might be avoided owing to a better match between item difficulty and examinee proficiency. The results are illustrated with simulated data, as well as with real data.
Empirical likelihood ratio tests for multivariate regression models
WU Jianhong; ZHU Lixing
2007-01-01
This paper proposes some diagnostic tools for checking the adequacy of multivariate regression models including classical regression and time series autoregression. In statistical inference, the empirical likelihood ratio method has been well known to be a powerful tool for constructing test and confidence region. For model checking, however, the naive empirical likelihood (EL) based tests are not of Wilks' phenomenon. Hence, we make use of bias correction to construct the EL-based score tests and derive a nonparametric version of Wilks' theorem. Moreover, by the advantages of both the EL and score test method, the EL-based score tests share many desirable features as follows: They are self-scale invariant and can detect the alternatives that converge to the null at rate n-1/2, the possibly fastest rate for lack-of-fit testing; they involve weight functions, which provides us with the flexibility to choose scores for improving power performance, especially under directional alternatives. Furthermore, when the alternatives are not directional, we construct asymptotically distribution-free maximin tests for a large class of possible alternatives. A simulation study is carried out and an application for a real dataset is analyzed.
Statistical analysis of concrete quality testing results
Jevtić Dragica
2014-01-01
Full Text Available This paper statistically investigates the testing results of compressive strength and density of control concrete specimens tested in the Laboratory for materials, Faculty of Civil Engineering, University of Belgrade, during 2012. The total number of 4420 concrete specimens were tested, which were sampled on different locations - either on concrete production site (concrete plant, or concrete placement location (construction site. To be exact, these samples were made of concrete which was produced on 15 concrete plants, i.e. placed in at 50 different reinforced concrete structures, built during 2012 by 22 different contractors. It is a known fact that the achieved values of concrete compressive strength are very important, both for quality and durability assessment of concrete inside the structural elements, as well as for calculation of their load-bearing capacity limit. Together with the compressive strength testing results, the data concerning requested (designed concrete class, matching between the designed and the achieved concrete quality, concrete density values and frequency of execution of concrete works during 2012 were analyzed.
Statistical modeling and MAP estimation for body fat quantification with MRI ratio imaging
Wong, Wilbur C. K.; Johnson, David H.; Wilson, David L.
2008-03-01
We are developing small animal imaging techniques to characterize the kinetics of lipid accumulation/reduction of fat depots in response to genetic/dietary factors associated with obesity and metabolic syndromes. Recently, we developed an MR ratio imaging technique that approximately yields lipid/{lipid + water}. In this work, we develop a statistical model for the ratio distribution that explicitly includes a partial volume (PV) fraction of fat and a mixture of a Rician and multiple Gaussians. Monte Carlo hypothesis testing showed that our model was valid over a wide range of coefficient of variation of the denominator distribution (c.v.: 0-0:20) and correlation coefficient among the numerator and denominator (ρ 0-0.95), which cover the typical values that we found in MRI data sets (c.v.: 0:027-0:063, ρ: 0:50-0:75). Then a maximum a posteriori (MAP) estimate for the fat percentage per voxel is proposed. Using a digital phantom with many PV voxels, we found that ratio values were not linearly related to PV fat content and that our method accurately described the histogram. In addition, the new method estimated the ground truth within +1.6% vs. +43% for an approach using an uncorrected ratio image, when we simply threshold the ratio image. On the six genetically obese rat data sets, the MAP estimate gave total fat volumes of 279 +/- 45mL, values 21% smaller than those from the uncorrected ratio images, principally due to the non-linear PV effect. We conclude that our algorithm can increase the accuracy of fat volume quantification even in regions having many PV voxels, e.g. ectopic fat depots.
Statistical reasoning in clinical trials: hypothesis testing.
Kelen, G D; Brown, C G; Ashton, J
1988-01-01
Hypothesis testing is based on certain statistical and mathematical principles that allow investigators to evaluate data by making decisions based on the probability or implausibility of observing the results obtained. However, classic hypothesis testing has its limitations, and probabilities mathematically calculated are inextricably linked to sample size. Furthermore, the meaning of the p value frequently is misconstrued as indicating that the findings are also of clinical significance. Finally, hypothesis testing allows for four possible outcomes, two of which are errors that can lead to erroneous adoption of certain hypotheses: 1. The null hypothesis is rejected when, in fact, it is false. 2. The null hypothesis is rejected when, in fact, it is true (type I or alpha error). 3. The null hypothesis is conceded when, in fact, it is true. 4. The null hypothesis is conceded when, in fact, it is false (type II or beta error). The implications of these errors, their relation to sample size, the interpretation of negative trials, and strategies related to the planning of clinical trials will be explored in a future article in this journal.
A Statistical Perspective on Highly Accelerated Testing
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
A Statistical Perspective on Highly Accelerated Testing.
Thomas, Edward V.
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
Statistical tests of simple earthquake cycle models
DeVries, Phoebe M. R.; Evans, Eileen L.
2016-12-01
A central goal of observing and modeling the earthquake cycle is to forecast when a particular fault may generate an earthquake: a fault late in its earthquake cycle may be more likely to generate an earthquake than a fault early in its earthquake cycle. Models that can explain geodetic observations throughout the entire earthquake cycle may be required to gain a more complete understanding of relevant physics and phenomenology. Previous efforts to develop unified earthquake models for strike-slip faults have largely focused on explaining both preseismic and postseismic geodetic observations available across a few faults in California, Turkey, and Tibet. An alternative approach leverages the global distribution of geodetic and geologic slip rate estimates on strike-slip faults worldwide. Here we use the Kolmogorov-Smirnov test for similarity of distributions to infer, in a statistically rigorous manner, viscoelastic earthquake cycle models that are inconsistent with 15 sets of observations across major strike-slip faults. We reject a large subset of two-layer models incorporating Burgers rheologies at a significance level of α = 0.05 (those with long-term Maxwell viscosities ηM 4.6 × 1020 Pa s) but cannot reject models on the basis of transient Kelvin viscosity ηK. Finally, we examine the implications of these results for the predicted earthquake cycle timing of the 15 faults considered and compare these predictions to the geologic and historical record.
Hypothesis testing and statistical analysis of microbiome
Yinglin Xia
2017-09-01
Full Text Available After the initiation of Human Microbiome Project in 2008, various biostatistic and bioinformatic tools for data analysis and computational methods have been developed and applied to microbiome studies. In this review and perspective, we discuss the research and statistical hypotheses in gut microbiome studies, focusing on mechanistic concepts that underlie the complex relationships among host, microbiome, and environment. We review the current available statistic tools and highlight recent progress of newly developed statistical methods and models. Given the current challenges and limitations in biostatistic approaches and tools, we discuss the future direction in developing statistical methods and models for the microbiome studies.
Chen Cao
2016-09-01
Full Text Available This study focused on producing flash flood hazard susceptibility maps (FFHSM using frequency ratio (FR and statistical index (SI models in the Xiqu Gully (XQG of Beijing, China. First, a total of 85 flash flood hazard locations (n = 85 were surveyed in the field and plotted using geographic information system (GIS software. Based on the flash flood hazard locations, a flood hazard inventory map was built. Seventy percent (n = 60 of the flooding hazard locations were randomly selected for building the models. The remaining 30% (n = 25 of the flooded hazard locations were used for validation. Considering that the XQG used to be a coal mining area, coalmine caves and subsidence caused by coal mining exist in this catchment, as well as many ground fissures. Thus, this study took the subsidence risk level into consideration for FFHSM. The ten conditioning parameters were elevation, slope, curvature, land use, geology, soil texture, subsidence risk area, stream power index (SPI, topographic wetness index (TWI, and short-term heavy rain. This study also tested different classification schemes for the values for each conditional parameter and checked their impacts on the results. The accuracy of the FFHSM was validated using area under the curve (AUC analysis. Classification accuracies were 86.61%, 83.35%, and 78.52% using frequency ratio (FR-natural breaks, statistical index (SI-natural breaks and FR-manual classification schemes, respectively. Associated prediction accuracies were 83.69%, 81.22%, and 74.23%, respectively. It was found that FR modeling using a natural breaks classification method was more appropriate for generating FFHSM for the Xiqu Gully.
Testing for Statistical Discrimination based on Gender
Lesner, Rune Vammen
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 but increases in job transitions and that the fraction of women in high-ranking positions within a firm does...... not affect the level of statistical discrimination by gender....
Statistical Decision Theory Estimation, Testing, and Selection
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
Filipiak, Katarzyna; Klein, Daniel; Roy, Anuradha
2017-01-01
The problem of testing the separability of a covariance matrix against an unstructured variance-covariance matrix is studied in the context of multivariate repeated measures data using Rao's score test (RST). The RST statistic is developed with the first component of the separable structure as a first-order autoregressive (AR(1)) correlation matrix or an unstructured (UN) covariance matrix under the assumption of multivariate normality. It is shown that the distribution of the RST statistic under the null hypothesis of any separability does not depend on the true values of the mean or the unstructured components of the separable structure. A significant advantage of the RST is that it can be performed for small samples, even smaller than the dimension of the data, where the likelihood ratio test (LRT) cannot be used, and it outperforms the standard LRT in a number of contexts. Monte Carlo simulations are then used to study the comparative behavior of the null distribution of the RST statistic, as well as that of the LRT statistic, in terms of sample size considerations, and for the estimation of the empirical percentiles. Our findings are compared with existing results where the first component of the separable structure is a compound symmetry (CS) correlation matrix. It is also shown by simulations that the empirical null distribution of the RST statistic converges faster than the empirical null distribution of the LRT statistic to the limiting χ(2) distribution. The tests are implemented on a real dataset from medical studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hsu Li; Helmer Quinta; de Visser Marieke CH; Uitte de Willige Shirley; el Galta Rachid; Houwing-Duistermaat Jeanine J
2007-01-01
Abstract Background: In this paper, we propose a one degree of freedom test for association between a candidate gene and a binary trait. This method is a generalization of Terwilliger's likelihood ratio statistic and is especially powerful for the situation of one associated haplotype. As an alternative to the likelihood ratio statistic, we derive a score statistic, which has a tractable expression. For haplotype analysis, we assume that phase is known. Results: By means of a simulation study...
Obtaining reliable Likelihood Ratio tests from simulated likelihood functions
Andersen, Laura Mørch
It is standard practice by researchers and the default option in many statistical programs to base test statistics for mixed models on simulations using asymmetric draws (e.g. Halton draws). This paper shows that when the estimated likelihood functions depend on standard deviations of mixed...
Scaling images using their background ratio. An application in statistical comparisons of images.
Kalemis, A; Binnie, D; Bailey, D L; Flower, M A; Ott, R J
2003-06-07
Comparison of two medical images often requires image scaling as a pre-processing step. This is usually done with the scaling-to-the-mean or scaling-to-the-maximum techniques which, under certain circumstances, in quantitative applications may contribute a significant amount of bias. In this paper, we present a simple scaling method which assumes only that the most predominant values in the corresponding images belong to their background structure. The ratio of the two images to be compared is calculated and its frequency histogram is plotted. The scaling factor is given by the position of the peak in this histogram which belongs to the background structure. The method was tested against the traditional scaling-to-the-mean technique on simulated planar gamma-camera images which were compared using pixelwise statistical parametric tests. Both sensitivity and specificity for each condition were measured over a range of different contrasts and sizes of inhomogeneity for the two scaling techniques. The new method was found to preserve sensitivity in all cases while the traditional technique resulted in significant degradation of sensitivity in certain cases.
Nearly Efficient Likelihood Ratio Tests of the Unit Root Hypothesis
Jansson, Michael; Nielsen, Morten Ørregaard
Seemingly absent from the arsenal of currently available "nearly efficient" testing procedures for the unit root hypothesis, i.e. tests whose local asymptotic power functions are indistinguishable from the Gaussian power envelope, is a test admitting a (quasi-)likelihood ratio interpretation. We...... show that the likelihood ratio unit root test derived in a Gaussian AR(1) model with standard normal innovations is nearly efficient in that model. Moreover, these desirable properties carry over to more complicated models allowing for serially correlated and/or non-Gaussian innovations....
Obtaining reliable likelihood ratio tests from simulated likelihood functions
Andersen, Laura Mørch
2014-01-01
likely to cause misleading test results for the number of draws usually used today. The paper illustrates that increasing the number of draws is a very inefficient solution strategy requiring very large numbers of draws to ensure against misleading test statistics. The main conclusion of this paper...
Statistical Tests for Mixed Linear Models
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
Wald Sequential Probability Ratio Test for Space Object Conjunction Assessment
Carpenter, James R.; Markley, F Landis
2014-01-01
This paper shows how satellite owner/operators may use sequential estimates of collision probability, along with a prior assessment of the base risk of collision, in a compound hypothesis ratio test to inform decisions concerning collision risk mitigation maneuvers. The compound hypothesis test reduces to a simple probability ratio test, which appears to be a novel result. The test satisfies tolerances related to targeted false alarm and missed detection rates. This result is independent of the method one uses to compute the probability density that one integrates to compute collision probability. A well-established test case from the literature shows that this test yields acceptable results within the constraints of a typical operational conjunction assessment decision timeline. Another example illustrates the use of the test in a practical conjunction assessment scenario based on operations of the International Space Station.
Dachian, Serguei
2010-01-01
Different change-point type models encountered in statistical inference for stochastic processes give rise to different limiting likelihood ratio processes. In a previous paper of one of the authors it was established that one of these likelihood ratios, which is an exponential functional of a two-sided Poisson process driven by some parameter, can be approximated (for sufficiently small values of the parameter) by another one, which is an exponential functional of a two-sided Brownian motion. In this paper we consider yet another likelihood ratio, which is the exponent of a two-sided compound Poisson process driven by some parameter. We establish, that similarly to the Poisson type one, the compound Poisson type likelihood ratio can be approximated by the Brownian type one for sufficiently small values of the parameter. We equally discuss the asymptotics for large values of the parameter and illustrate the results by numerical simulations.
Statistical tests of galactic dynamo theory
Chamandy, Luke; Taylor, A Russ
2016-01-01
Mean-field galactic dynamo theory is the leading theory to explain the prevalence of regular magnetic fields in spiral galaxies, but its systematic comparison with observations is still incomplete and fragmentary. Here we compare predictions of mean-field dynamo models to observational data on magnetic pitch angle and the strength of the mean magnetic field. We demonstrate that a standard $\\alpha^2\\Omega$ dynamo model produces pitch angles of the regular magnetic fields of nearby galaxies that are reasonably consistent with available data. The dynamo estimates of the magnetic field strength are generally within a factor of a few of the observational values. Reasonable agreement between theoretical and observed pitch angles generally requires the turbulent correlation time $\\tau$ to be in the range 10-20 Myr, in agreement with standard estimates. Moreover, good agreement also requires that the ratio of the ionized gas scale height to root-mean-square turbulent velocity increases with radius. Our results thus w...
Caveats for using statistical significance tests in research assessments
2011-01-01
This paper 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. Statistical significance tests are highly 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 s...
Assessing Statistical Aspects of Test Fairness with Structural Equation Modelling
Kline, Rex B.
2013-01-01
Test fairness and test bias are not synonymous concepts. Test bias refers to statistical evidence that the psychometrics or interpretation of test scores depend on group membership, such as gender or race, when such differences are not expected. A test that is grossly biased may be judged to be unfair, but test fairness concerns the broader, more…
A note on measurement scales and statistical testing
Meijer, R.R.; Oosterloo, Sebe J.
2008-01-01
In elementary books on applied statistics (e.g., Siegel, 1988; Agresti, 1990) and books on research methodology in psychology and personality assessment (e.g., Aiken, 1999), it is often suggested that the choice of a statistical test and the choice of statistical operations should be determined by
A note on measurement scales and statistical testing
Meijer, Rob R.; Oosterloo, Sebie J.
2008-01-01
In elementary books on applied statistics (e.g., Siegel, 1988; Agresti, 1990) and books on research methodology in psychology and personality assessment (e.g., Aiken, 1999), it is often suggested that the choice of a statistical test and the choice of statistical operations should be determined by t
A statistical procedure for testing financial contagion
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.
A Molecular Diode with a Statistically Robust Rectification Ratio of Three Orders of Magnitude.
Yuan, Li; Breuer, Rochus; Jiang, Li; Schmittel, Michael; Nijhuis, Christian A
2015-08-12
This paper describes a molecular diode with high, statistically robust, rectification ratios R of 1.1 × 10(3). These diodes operate with a new mechanism of charge transport based on sequential tunneling involving both the HOMO and HOMO-1 positioned asymmetrically inside the junction. In addition, the diodes are stable and withstand voltage cycling for 1500 times, and the yield in working junctions is 90%.
Caveats for using statistical significance tests in research assessments
Schneider, Jesper W
2011-01-01
This paper 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. Statistical significance tests are highly 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 of such tests, their dichotomous application in decision making, the difference between statistical and substantive significance, the implausibility of most null hypotheses, the crucial assumption of randomness, as well as the utility of standard errors and confidence intervals for inferential purposes. We argue that applying statistical significance tests and mechanically adhering to their results is highly problematic and detrimental to critical thinki...
Distinguish Dynamic Basic Blocks by Structural Statistical Testing
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 satisfying a structural coverage criterion for instance. In this paper, we propose a new statistical testing method that generates sequences of random test data that respect the following probabilistic properties: 1) each sequence guarantees the uniform selection of feasible paths only and 2) the uniform...... 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...
Misuse of statistical test in three decades of psychotherapy research.
Dar, R; Serlin, R C; Omer, H
1994-02-01
This article reviews the misuse of statistical tests in psychotherapy research studies published in the Journal of Consulting and Clinical Psychology in the years 1967-1968, 1977-1978, and 1987-1988. It focuses on 3 major problems in statistical practice: inappropriate uses of null hypothesis tests and p values, neglect of effect size, and inflation of Type I error rate. The impressive frequency of these problems is documented, and changes in statistical practices over the past 3 decades are interpreted in light of trends in psychotherapy research. The article concludes with practical suggestions for rational application of statistical tests.
A detailed description of the sequential probability ratio test for 2-IMU FDI
Rich, T. M.
1976-01-01
The sequential probability ratio test (SPRT) for 2-IMU FDI (inertial measuring unit failure detection/isolation) is described. The SPRT is a statistical technique for detecting and isolating soft IMU failures originally developed for the strapdown inertial reference unit. The flowchart of a subroutine incorporating the 2-IMU SPRT is included.
Quantum Hypothesis Testing and Non-Equilibrium Statistical Mechanics
Jaksic, V; Pillet, C -A; Seiringer, R
2011-01-01
We extend the mathematical theory of quantum hypothesis testing to the general $W^*$-algebraic setting and explore its relation with recent developments in non-equilibrium quantum statistical mechanics. In particular, we relate the large deviation principle for the full counting statistics of entropy flow to quantum hypothesis testing of the arrow of time.
Statistical Tests of the PTHA Poisson Assumption for Submarine Landslides
Geist, E. L.; Chaytor, J. D.; Parsons, T.; Ten Brink, U. S.
2012-12-01
We demonstrate that a sequence of dated mass transport deposits (MTDs) can provide information to statistically test whether or not submarine landslides associated with these deposits conform to a Poisson model of occurrence. Probabilistic tsunami hazard analysis (PTHA) most often assumes Poissonian occurrence for all sources, with an exponential distribution of return times. Using dates that define the bounds of individual MTDs, we first describe likelihood and Monte Carlo methods of parameter estimation for a suite of candidate occurrence models (Poisson, lognormal, gamma, Brownian Passage Time). In addition to age-dating uncertainty, both methods incorporate uncertainty caused by the open time intervals: i.e., before the first and after the last event to the present. Accounting for these open intervals is critical when there are a small number of observed events. The optimal occurrence model is selected according to both the Akaike Information Criteria (AIC) and Akaike's Bayesian Information Criterion (ABIC). In addition, the likelihood ratio test can be performed on occurrence models from the same family: e.g., the gamma model relative to the exponential model of return time distribution. Parameter estimation, model selection, and hypothesis testing are performed on data from two IODP holes in the northern Gulf of Mexico that penetrated a total of 14 MTDs, some of which are correlated between the two holes. Each of these events has been assigned an age based on microfossil zonations and magnetostratigraphic datums. Results from these sites indicate that the Poisson assumption is likely valid. However, parameter estimation results using the likelihood method for one of the sites suggest that the events may have occurred quasi-periodically. Methods developed in this study provide tools with which one can determine both the rate of occurrence and the statistical validity of the Poisson assumption when submarine landslides are included in PTHA.
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.
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
Caveats for using statistical significance tests in research assessments
Schneider, Jesper Wiborg
2013-01-01
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...... 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...... of such tests, their dichotomous application in decision making, the difference between statistical and substantive significance, the implausibility of most null hypotheses, the crucial assumption of randomness, as well as the utility of standard errors and confidence intervals for inferential purposes. We...
Caveats for using statistical significance tests in research assessments
Schneider, Jesper Wiborg
2013-01-01
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...... 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...... are important or not. On the contrary their use may be harmful. Like many other critics, we generally believe that statistical significance tests are over- and misused in the empirical sciences including scientometrics and we encourage a reform on these matters....
A Note on Three Statistical Tests in the Logistic Regression DIF Procedure
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…
A Note on Three Statistical Tests in the Logistic Regression DIF Procedure
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…
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 loc
Razavi, R.; Dehghani, V.
2014-03-01
The entropy excess of 163Dy compared to 162Dy as a function of nuclear temperature have been investigated using the mean value Bardeen-Cooper-Schrieffer (BCS) method based on application of the isothermal probability distribution function to take into account the statistical fluctuations. Then, the spin cut-off excess ratio (moment of inertia excess ratio) introduced by Razavi [Phys. Rev. C88 (2013) 014316] for proton and neutron system have been obtained and are compared with their corresponding data on the BCS model. The results show that the overall agreement between the BCS model and mean value BCS method is satisfactory and the mean value BCS model reduces fluctuations and washes out singularities. However, the expected constant value in the entropy excess is not reproduced by the mean value BCS method.
Sanabria, Federico; Killeen, Peter R.
2007-01-01
Despite being under challenge for the past 50 years, null hypothesis significance testing (NHST) remains dominant in the scientific field for want of viable alternatives. NHST, along with its significance level "p," is inadequate for most of the uses to which it is put, a flaw that is of particular interest to educational practitioners…
Misuse of statistical tests in Archives of Clinical Neuropsychology publications.
Schatz, Philip; Jay, Kristin A; McComb, Jason; McLaughlin, Jason R
2005-12-01
This article reviews the (mis)use of statistical tests in neuropsychology research studies published in the Archives of Clinical Neuropsychology in the years 1990-1992 and 1996-2000, and 2001-2004, prior to, commensurate with the internet-based and paper-based release, and following the release of the American Psychological Association's Task Force on Statistical Inference. The authors focused on four statistical errors: inappropriate use of null hypothesis tests, inappropriate use of P-values, neglect of effect size, and inflation of Type I error rates. Despite the recommendations of the Task Force on Statistical Inference published in 1999, the present study recorded instances of these statistical errors both pre- and post-APA's report, with only the reporting of effect size increasing after the release of the report. Neuropsychologists involved in empirical research should be better aware of the limitations and boundaries of hypothesis testing as well as the theoretical aspects of research methodology.
The Use of Meta-Analytic Statistical Significance Testing
Polanin, Joshua R.; Pigott, Terri D.
2015-01-01
Meta-analysis multiplicity, the concept of conducting multiple tests of statistical significance within one review, is an underdeveloped literature. We address this issue by considering how Type I errors can impact meta-analytic results, suggest how statistical power may be affected through the use of multiplicity corrections, and propose how…
CUSUM-Based Person-Fit Statistics for Adaptive Testing.
van Krimpen-Stoop, Edith M. L. A.; Meijer, Rob R.
2001-01-01
Proposed person-fit statistics that are designed for use in a computerized adaptive test (CAT) and derived critical values for these statistics using cumulative sum (CUSUM) procedures so that item-score patterns can be classified as fitting or misfitting. Compared nominal Type I errors with empirical Type I errors through simulation studies. (SLD)
BIAZA statistics guidelines: toward a common application of statistical tests for zoo research.
Plowman, Amy B
2008-05-01
Zoo research presents many statistical challenges, mostly arising from the need to work with small sample sizes. Efforts to overcome these often lead to the misuse of statistics including pseudoreplication, inappropriate pooling, assumption violation or excessive Type II errors because of using tests with low power to avoid assumption violation. To tackle these issues and make some general statistical recommendations for zoo researchers, the Research Group of the British and Irish Association of Zoos and Aquariums (BIAZA) conducted a workshop. Participants included zoo-based researchers, university academics with zoo interests and three statistical experts. The result was a BIAZA publication Zoo Research Guidelines: Statistics for Typical Zoo Datasets (Plowman [2006] Zoo research guidelines: statistics for zoo datasets. London: BIAZA), which provides advice for zoo researchers on study design and analysis to ensure appropriate and rigorous use of statistics. The main recommendations are: (1) that many typical zoo investigations should be conducted as single case/small N randomized designs, analyzed with randomization tests, (2) that when comparing complete time budgets across conditions in behavioral studies, G tests and their derivatives are the most appropriate statistical tests and (3) that in studies involving multiple dependent and independent variables there are usually no satisfactory alternatives to traditional parametric tests and, despite some assumption violations, it is better to use these tests with careful interpretation, than to lose information through not testing at all. The BIAZA guidelines were recommended by American Association of Zoos and Aquariums (AZA) researchers at the AZA Annual Conference in Tampa, FL, September 2006, and are free to download from www.biaza.org.uk.
Evaluation of Multi-parameter Test Statistics for Multiple Imputation.
Liu, Yu; Enders, Craig K
2017-01-01
In Ordinary Least Square regression, researchers often are interested in knowing whether a set of parameters is different from zero. With complete data, this could be achieved using the gain in prediction test, hierarchical multiple regression, or an omnibus F test. However, in substantive research scenarios, missing data often exist. In the context of multiple imputation, one of the current state-of-art missing data strategies, there are several different analogous multi-parameter tests of the joint significance of a set of parameters, and these multi-parameter test statistics can be referenced to various distributions to make statistical inferences. However, little is known about the performance of these tests, and virtually no research study has compared the Type 1 error rates and statistical power of these tests in scenarios that are typical of behavioral science data (e.g., small to moderate samples, etc.). This paper uses Monte Carlo simulation techniques to examine the performance of these multi-parameter test statistics for multiple imputation under a variety of realistic conditions. We provide a number of practical recommendations for substantive researchers based on the simulation results, and illustrate the calculation of these test statistics with an empirical example.
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.
The null distribution of likelihood-ratio statistics in the conditional-logistic linkage model.
Song, Yeunjoo E; Elston, Robert C
2013-01-01
Olson's conditional-logistic model retains the nice property of the LOD score formulation and has advantages over other methods that make it an appropriate choice for complex trait linkage mapping. However, the asymptotic distribution of the conditional-logistic likelihood-ratio (CL-LR) statistic with genetic constraints on the model parameters is unknown for some analysis models, even in the case of samples comprising only independent sib pairs. We derive approximations to the asymptotic null distributions of the CL-LR statistics and compare them with the empirical null distributions by simulation using independent affected sib pairs. Generally, the empirical null distributions of the CL-LR statistics match well the known or approximated asymptotic distributions for all analysis models considered except for the covariate model with a minimum-adjusted binary covariate. This work will provide useful guidelines for linkage analysis of real data sets for the genetic analysis of complex traits, thereby contributing to the identification of genes for disease traits.
Statistical Evaluation of Molecular Contamination During Spacecraft Thermal Vacuum Test
Chen, Philip; Hedgeland, Randy; Montoya, Alex; Roman-Velazquez, Juan; Dunn, Jamie; Colony, Joe; Petitto, Joseph
1999-01-01
The purpose of this paper is to evaluate the statistical molecular contamination data with a goal to improve spacecraft contamination control. The statistical data was generated in typical thermal vacuum tests at the National Aeronautics and Space Administration, Goddard Space Flight Center (GSFC). The magnitude of material outgassing was measured using a Quartz Crystal Microbalance (QCNO device during the test. A solvent rinse sample was taken at the conclusion of each test. Then detailed qualitative and quantitative measurements were obtained through chemical analyses. All data used in this study encompassed numerous spacecraft tests in recent years.
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....
Rabinowitz, Daniel
2003-05-01
The focus of this work is the TDT-type and family-based test statistics used for adjusting for potential confounding due to population heterogeneity or misspecified allele frequencies. A variety of heuristics have been used to motivate and derive these statistics, and the statistics have been developed for a variety of analytic goals. There appears to be no general theoretical framework, however, that may be used to evaluate competing approaches. Furthermore, there is no framework to guide the development of efficient TDT-type and family-based methods for analytic goals for which methods have not yet been proposed. The purpose of this paper is to present a theoretical framework that serves both to identify the information which is available to methods that are immune to confounding due to population heterogeneity or misspecified allele frequencies, and to inform the construction of efficient unbiased tests in novel settings. The development relies on the existence of a characterization of the null hypothesis in terms of a completely specified conditional distribution of transmitted genotypes. An important observation is that, with such a characterization, when the conditioning event is unobserved or incomplete, there is statistical information that cannot be exploited by any exact conditional test. The main technical result of this work is an approach to computing test statistics for local alternatives that exploit all of the available statistical information. Copyright 2003 Wiley-Liss, Inc.
Log-concave Probability Distributions: Theory and Statistical Testing
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...
Scale invariant for one-sided multivariate likelihood ratio tests
Samruam Chongcharoen
2010-07-01
Full Text Available Suppose 1 2 , ,..., n X X X is a random sample from Np ( ,V distribution. Consider 0 1 2 : ... 0 p H and1 : 0 for 1, 2,..., i H i p , let 1 0 H H denote the hypothesis that 1 H holds but 0 H does not, and let ~ 0 H denote thehypothesis that 0 H does not hold. Because the likelihood ratio test (LRT of 0 H versus 1 0 H H is complicated, severalad hoc tests have been proposed. Tang, Gnecco and Geller (1989 proposed an approximate LRT, Follmann (1996 suggestedrejecting 0 H if the usual test of 0 H versus ~ 0 H rejects 0 H with significance level 2 and a weighted sum of the samplemeans is positive, and Chongcharoen, Singh and Wright (2002 modified Follmann’s test to include information about thecorrelation structure in the sum of the sample means. Chongcharoen and Wright (2007, 2006 give versions of the Tang-Gnecco-Geller tests and Follmann-type tests, respectively, with invariance properties. With LRT’s scale invariant desiredproperty, we investigate its powers by using Monte Carlo techniques and compare them with the tests which we recommendin Chongcharoen and Wright (2007, 2006.
Melo, Tatiane F N; Patriota, Alexandre G
2012-01-01
In this paper, we develop a modified version of the likelihood ratio test for multivariate heteroskedastic errors-in-variables regression models. The error terms are allowed to follow a multivariate distribution in the elliptical class of distributions, which has the normal distribution as a special case. We derive the Skovgaard adjusted likelihood ratio statistic, which follows a chi-squared distribution with a high degree of accuracy. We conduct a simulation study and show that the proposed test displays superior finite sample behavior as compared to the standard likelihood ratio test. We illustrate the usefulness of our results in applied settings using a data set from the WHO MONICA Project on cardiovascular disease.
Accelerated testing statistical models, test plans, and data analysis
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.
CUSUM-based person-fit statistics for adaptive testing
Krimpen-Stoop, van Edith M.L.A.; Meijer, Rob 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), t
Statistical Measures of Integrity in Online Testing: Empirical Study
Wielicki, Tom
2016-01-01
This paper reports on longitudinal study regarding integrity of testing in an online format as used by e-learning platforms. Specifically, this study explains whether online testing, which implies an open book format is compromising integrity of assessment by encouraging cheating among students. Statistical experiment designed for this study…
Statistical significance test for transition matrices of atmospheric Markov chains
Vautard, Robert; Mo, Kingtse C.; Ghil, Michael
1990-01-01
Low-frequency variability of large-scale atmospheric dynamics can be represented schematically by a Markov chain of multiple flow regimes. This Markov chain contains useful information for the long-range forecaster, provided that the statistical significance of the associated transition matrix can be reliably tested. Monte Carlo simulation yields a very reliable significance test for the elements of this matrix. The results of this test agree with previously used empirical formulae when each cluster of maps identified as a distinct flow regime is sufficiently large and when they all contain a comparable number of maps. Monte Carlo simulation provides a more reliable way to test the statistical significance of transitions to and from small clusters. It can determine the most likely transitions, as well as the most unlikely ones, with a prescribed level of statistical significance.
Sequential Probability Ratio Test for Collision Avoidance Maneuver Decisions
Carpenter, J. Russell; Markley, F. Landis
2010-01-01
When facing a conjunction between space objects, decision makers must chose whether to maneuver for collision avoidance or not. We apply a well-known decision procedure, the sequential probability ratio test, to this problem. We propose two approaches to the problem solution, one based on a frequentist method, and the other on a Bayesian method. The frequentist method does not require any prior knowledge concerning the conjunction, while the Bayesian method assumes knowledge of prior probability densities. Our results show that both methods achieve desired missed detection rates, but the frequentist method's false alarm performance is inferior to the Bayesian method's
Radiation detection method and system using the sequential probability ratio test
Nelson, Karl E.; Valentine, John D.; Beauchamp, Brock R.
2007-07-17
A method and system using the Sequential Probability Ratio Test to enhance the detection of an elevated level of radiation, by determining whether a set of observations are consistent with a specified model within a given bounds of statistical significance. In particular, the SPRT is used in the present invention to maximize the range of detection, by providing processing mechanisms for estimating the dynamic background radiation, adjusting the models to reflect the amount of background knowledge at the current point in time, analyzing the current sample using the models to determine statistical significance, and determining when the sample has returned to the expected background conditions.
Detection of Invalid Test Scores on Admission Tests : A Simulation Study Using Person-Fit Statistics
Tendeiro, Jorge N.; Meijer, Rob R.; Albers, Casper J.
While an admission test may strongly predict success in university or law school programs for most test takers, there may be some test takers who are mismeasured. To address this issue, a class of statistics called person-fit statistics is used to check the validity of individual test scores.
Sequential Probability Ratio Test for Spacecraft Collision Avoidance Maneuver Decisions
Carpenter, J. Russell; Markley, F. Landis
2013-01-01
A document discusses sequential probability ratio tests that explicitly allow decision-makers to incorporate false alarm and missed detection risks, and are potentially less sensitive to modeling errors than a procedure that relies solely on a probability of collision threshold. Recent work on constrained Kalman filtering has suggested an approach to formulating such a test for collision avoidance maneuver decisions: a filter bank with two norm-inequality-constrained epoch-state extended Kalman filters. One filter models the null hypotheses that the miss distance is inside the combined hard body radius at the predicted time of closest approach, and one filter models the alternative hypothesis. The epoch-state filter developed for this method explicitly accounts for any process noise present in the system. The method appears to work well using a realistic example based on an upcoming, highly elliptical orbit formation flying mission.
Vrbos, L A; Lorenz, M A; Peabody, E H; McGregor, M
1993-06-15
An analysis of 300 randomly drawn orthopaedic spine articles, published between 1970 and 1990, was performed to assess the quality of biostatistical testing and research design reported in the literature. Of the 300 articles, 269 dealt with topics of an experimental nature, while 31 documented descriptive studies. Statistical deficiencies were identified in 54.0% of the total articles. Conclusions drawn as the result of misleading significance values occurred in 124 experimental studies (46%) while 96 failed to document the form of analysis chosen (35.7%). Statistical testing was not documented in 34 studies (12.6%), while 20 (7.4%) employed analyses considered inappropriate for the specific design structure.
Model of risk assessment under ballistic statistical tests
Gabrovski, Ivan; Karakaneva, Juliana
The material presents the application of a mathematical method for risk assessment under statistical determination of the ballistic limits of the protection equipment. The authors have implemented a mathematical model based on Pierson's criteria. The software accomplishment of the model allows to evaluate the V50 indicator and to assess the statistical hypothesis' reliability. The results supply the specialists with information about the interval valuations of the probability determined during the testing process.
Deep, Low Mass Ratio Overcontact Binary Systems. XIV. A Statistical Analysis of 46 Sample Binaries
Yang, Yuan-Gui; Qian, Sheng-Bang
2015-09-01
A sample of 46 deep, low mass ratio (DLMR) overcontact binaries (i.e., q≤slant 0.25 and f≥slant 50%) is statistically analyzed in this paper. It is found that five relations possibly exist among some physical parameters. The primary components are little-evolved main sequence stars that lie between the zero-age main sequence line and the terminal-age main sequence (TAMS) line. Meanwhile, the secondary components may be evolved stars above the TAMS line. The super-luminosities and large radii may result from energy transfer, which causes their volumes to expand. The equations of M-L and M-R for the components are also determined. The relation of P-Mtotal implies that mass may escape from the central system when the orbital period decreases. The minimum mass ratio may preliminarily be {q}{min}=0.044(+/- 0.007) from the relations of q-f and q-Jspin/Jorb. With mass and angular momentum loss, the orbital period decreases, which finally causes this kind of DLMR overcontact binary to merge into a rapid-rotating single star.
The selection of testing methods for biofuels using the Taguchi signal-to-noise ratio
Irusta, R. (Valladolid Univ. (Spain). Dept. de Ingenieria Quimica Centro Regional para la Promocion de la Calidad en Castilla y Leon (A.E.C.C.), Valladolid (Spain)); Antolin, G.; Velasco, E.; Garcia, J.C. (Valladolid Univ. (Spain). Dept. de Ingenieria Quimica)
1994-01-01
This paper describes a statistical criterion for evaluation and selection of different testing methods for solid biofuels taking into consideration accuracy, precision, sensitivity, reproducibility, repeatability, testing costs and testing time. The signal-to-noise ratio as suggested by Taguchi has been used in a way similar to a traditional method (analysis of variance, ANOVA) used for this purpose. Some simulated examples are described to illustrate the development of the proposed technique. Application to real situations can be made by treating experimental data in a similar way. (Author)
A likelihood ratio test for species membership based on DNA sequence data
Matz, Mikhail V.; Nielsen, Rasmus
2005-01-01
DNA barcoding as an approach for species identification is rapidly increasing in popularity. However, it remains unclear which statistical procedures should accompany the technique to provide a measure of uncertainty. Here we describe a likelihood ratio test which can be used to test if a sampled...... sequence is a member of an a priori specified species. We investigate the performance of the test using coalescence simulations, as well as using the real data from butterflies and frogs representing two kinds of challenge for DNA barcoding: extremely low and extremely high levels of sequence variability....
Piper, Thomas; Emery, Caroline; Thomas, Andreas; Saugy, Martial; Thevis, Mario
2013-06-01
Carbon isotope ratio (CIR) analysis has been routinely and successfully applied to doping control analysis for many years to uncover the misuse of endogenous steroids such as testosterone. Over the years, several challenges and limitations of this approach became apparent, e.g., the influence of inadequate chromatographic separation on CIR values or the emergence of steroid preparations comprising identical CIRs as endogenous steroids. While the latter has been addressed recently by the implementation of hydrogen isotope ratios (HIR), an improved sample preparation for CIR avoiding co-eluting compounds is presented herein together with newly established reference values of those endogenous steroids being relevant for doping controls. From the fraction of glucuronidated steroids 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-Hydroxy-5β-androstane-11,17-dione, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 3β-hydroxy-androst-5-en-17-one (DHEA), 5α- and 5β-androstane-3α,17β-diol (5aDIOL and 5bDIOL), 17β-hydroxy-androst-4-en-3-one and 17α-hydroxy-androst-4-en-3-one were included. In addition, sulfate conjugates of ANDRO, ETIO, DHEA, 3β-hydroxy-5α-androstan-17-one plus 17α- and androst-5-ene-3β,17β-diol were considered and analyzed after acidic solvolysis. The results obtained for the reference population encompassing n = 67 males and females confirmed earlier findings regarding factors influencing endogenous CIR. Variations in sample preparation influenced CIR measurements especially for 5aDIOL and 5bDIOL, the most valuable steroidal analytes for the detection of testosterone misuse. Earlier investigations on the HIR of the same reference population enabled the evaluation of combined measurements of CIR and HIR and its usefulness regarding both steroid metabolism studies and doping control analysis. The combination of both stable isotopes would allow for lower reference limits providing the same statistical
Distributions of Hardy-Weinberg equilibrium test statistics.
Rohlfs, R V; Weir, B S
2008-11-01
It is well established that test statistics and P-values derived from discrete data, such as genetic markers, are also discrete. In most genetic applications, the null distribution for a discrete test statistic is approximated with a continuous distribution, but this approximation may not be reasonable. In some cases using the continuous approximation for the expected null distribution may cause truly null test statistics to appear nonnull. We explore the implications of using continuous distributions to approximate the discrete distributions of Hardy-Weinberg equilibrium test statistics and P-values. We derive exact P-value distributions under the null and alternative hypotheses, enabling a more accurate analysis than is possible with continuous approximations. We apply these methods to biological data and find that using continuous distribution theory with exact tests may underestimate the extent of Hardy-Weinberg disequilibrium in a sample. The implications may be most important for the widespread use of whole-genome case-control association studies and Hardy-Weinberg equilibrium (HWE) testing for data quality control.
[Clinical research IV. Relevancy of the statistical test chosen].
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).
On the Correct Use of Statistical Tests: Reply to "Lies, damned lies and statistics (in Geology)"
Sornette, D
2010-01-01
In a recent Forum in EOS entitled "Lies, damned lies and statistics (in Geology)", Vermeesch (2009) claims that "statistical significant is not the same as geological significant", in other words, statistical tests may be misleading. In complete contradiction, we affirm that statistical tests are always informative. We trace the erroneous claim of Vermeesch (2009) to a mistake in the interpretation of the chi-square test. Furthermore, using the same catalog of 118,415 earthquakes of magnitude 4 or greater and occurring between Friday 1st January 1999 and Thursday, 1 January 2009 (USGS, http://earthquake.usgs.gov), we show that the null hypothesis that "the occurrence of earthquakes does not depend on the day of the week" cannot be rejected (p-value equal to p=0.46), when taking into account the two well-known effects of (i) catalog incompleteness and (ii) aftershock clustering. This corrects the p-value p=4.5 10^{-18} found by P. Vermeesch (2009), whose implementation of the chi-square test assumes that the 1...
688,112 statistical results : Content mining psychology articles for statistical test results
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
ROTS: An R package for reproducibility-optimized statistical testing.
Suomi, Tomi; Seyednasrollah, Fatemeh; Jaakkola, Maria K; Faux, Thomas; Elo, Laura L
2017-05-01
Differential expression analysis is one of the most common types of analyses performed on various biological data (e.g. RNA-seq or mass spectrometry proteomics). It is the process that detects features, such as genes or proteins, showing statistically significant differences between the sample groups under comparison. A major challenge in the analysis is the choice of an appropriate test statistic, as different statistics have been shown to perform well in different datasets. To this end, the reproducibility-optimized test statistic (ROTS) adjusts a modified t-statistic according to the inherent properties of the data and provides a ranking of the features based on their statistical evidence for differential expression between two groups. ROTS has already been successfully applied in a range of different studies from transcriptomics to proteomics, showing competitive performance against other state-of-the-art methods. To promote its widespread use, we introduce here a Bioconductor R package for performing ROTS analysis conveniently on different types of omics data. To illustrate the benefits of ROTS in various applications, we present three case studies, involving proteomics and RNA-seq data from public repositories, including both bulk and single cell data. The package is freely available from Bioconductor (https://www.bioconductor.org/packages/ROTS).
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...
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...
Generalized Hypergeometric Ensembles: Statistical Hypothesis Testing in Complex Networks
Casiraghi, Giona; Scholtes, Ingo; Schweitzer, Frank
2016-01-01
Statistical ensembles define probability spaces of all networks consistent with given aggregate statistics and have become instrumental in the analysis of relational data on networked systems. Their numerical and analytical study provides the foundation for the inference of topological patterns, the definition of network-analytic measures, as well as for model selection and statistical hypothesis testing. Contributing to the foundation of these important data science techniques, in this article we introduce generalized hypergeometric ensembles, a framework of analytically tractable statistical ensembles of finite, directed and weighted networks. This framework can be interpreted as a generalization of the classical configuration model, which is commonly used to randomly generate networks with a given degree sequence or distribution. Our generalization rests on the introduction of dyadic link propensities, which capture the degree-corrected tendencies of pairs of nodes to form edges between each other. Studyin...
Probing dark energy with the shear-ratio geometric test
Taylor, A N; Bacon, D J; Heavens, A F
2006-01-01
We adapt the Jain--Taylor (2003) shear-ratio geometric lensing method to measure the dark energy equation of state, and its time derivative from dark matter haloes in cosmologies with arbitrary spatial curvature. The full shear-ratio covariance matrix is calculated for lensed sources, including the intervening large-scale structure and photometric redshift errors as additional sources of noise, and a maximum likelihood method for applying the test is presented. Combining with the expected results from the CMB we design an optimal survey for probing dark energy. A targeted survey imaging 60 of the largest clusters in a hemisphere with 5-band optical photometric redshifts to a median galaxy depth of zm=0.9 could measure w0 to a marginal 1-sigma error of $\\Delta$w0=0.4. We marginalize over all other parameters including wa, where the equation of state is parameterized in terms of scale factor a as w(a)=w0+wa(1-a). For higher accuracy a large-scale photometric redshift survey is required. Such a near-future 5-ban...
Reliability Evaluation of Concentric Butterfly Valve Using Statistical Hypothesis Test
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.
Yuan, Ke-Hai
2008-01-01
In the literature of mean and covariance structure analysis, noncentral chi-square distribution is commonly used to describe the behavior of the likelihood ratio (LR) statistic under alternative hypothesis. Due to the inaccessibility of the rather technical literature for the distribution of the LR statistic, it is widely believed that the…
Interactive comparison of hypothesis tests for statistical model checking
de Boer, Pieter-Tjerk; Reijsbergen, D.P.; Scheinhardt, Willem R.W.
2015-01-01
We present a web-based interactive comparison of hypothesis tests as are used in statistical model checking, providing users and tool developers with more insight into their characteristics. Parameters can be modified easily and their influence is visualized in real time; an integrated simulation
The performance of robust test statistics with categorical data
Savalei, V.; Rhemtulla, M.
2013-01-01
This paper reports on a simulation study that evaluated the performance of five structural equation model test statistics appropriate for categorical data. Both Type I error rate and power were investigated. Different model sizes, sample sizes, numbers of categories, and threshold distributions were
The performance of robust test statistics with categorical data
Savalei, V.; Rhemtulla, M.
2013-01-01
This paper reports on a simulation study that evaluated the performance of five structural equation model test statistics appropriate for categorical data. Both Type I error rate and power were investigated. Different model sizes, sample sizes, numbers of categories, and threshold distributions were
Evaluation of the Wishart test statistics for polarimetric SAR data
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...
Equivalence versus classical statistical tests in water quality assessments.
Ngatia, Murage; Gonzalez, David; San Julian, Steve; Conner, Arin
2010-01-01
To evaluate whether two unattended field organic carbon instruments could provide data comparable to laboratory-generated data, we needed a practical assessment. Null hypothesis statistical testing (NHST) is commonly utilized for such evaluations in environmental assessments, but researchers in other disciplines have identified weaknesses that may limit NHST's usefulness. For example, in NHST, large sample sizes change p-values and a statistically significant result can be obtained by merely increasing the sample size. In addition, p-values can indicate that observed results are statistically significantly different, but in reality the differences could be trivial in magnitude. Equivalence tests, on the other hand, allow the investigator to incorporate decision criteria that have practical relevance to the study. In this paper, we demonstrate the potential use of equivalence tests as an alternative to NHST. We first compare data between the two field instruments, and then compare the field instruments' data to laboratory-generated data using both NHST and equivalence tests. NHST indicated that the data between the two field instruments and the data between the field instruments and the laboratory were significantly different. Equivalence tests showed that the data were equivalent because they fell within a pre-determined equivalence interval based on our knowledge of laboratory precision. We conclude that equivalence tests provide more useful comparisons and interpretation of water quality data than NHST and should be more widely used in similar environmental assessments.
Poage, J. L.
1975-01-01
A sequential nonparametric pattern classification procedure is presented. The method presented is an estimated version of the Wald sequential probability ratio test (SPRT). This method utilizes density function estimates, and the density estimate used is discussed, including a proof of convergence in probability of the estimate to the true density function. The classification procedure proposed makes use of the theory of order statistics, and estimates of the probabilities of misclassification are given. The procedure was tested on discriminating between two classes of Gaussian samples and on discriminating between two kinds of electroencephalogram (EEG) responses.
Wavelet analysis in ecology and epidemiology: impact of statistical tests.
Cazelles, Bernard; Cazelles, Kévin; Chavez, Mario
2014-02-06
Wavelet analysis is now frequently used to extract information from ecological and epidemiological time series. Statistical hypothesis tests are conducted on associated wavelet quantities to assess the likelihood that they are due to a random process. Such random processes represent null models and are generally based on synthetic data that share some statistical characteristics with the original time series. This allows the comparison of null statistics with those obtained from original time series. When creating synthetic datasets, different techniques of resampling result in different characteristics shared by the synthetic time series. Therefore, it becomes crucial to consider the impact of the resampling method on the results. We have addressed this point by comparing seven different statistical testing methods applied with different real and simulated data. Our results show that statistical assessment of periodic patterns is strongly affected by the choice of the resampling method, so two different resampling techniques could lead to two different conclusions about the same time series. Moreover, our results clearly show the inadequacy of resampling series generated by white noise and red noise that are nevertheless the methods currently used in the wide majority of wavelets applications. Our results highlight that the characteristics of a time series, namely its Fourier spectrum and autocorrelation, are important to consider when choosing the resampling technique. Results suggest that data-driven resampling methods should be used such as the hidden Markov model algorithm and the 'beta-surrogate' method.
Statistical tests for associations between two directed acyclic graphs.
Robert Hoehndorf
Full Text Available Biological data, and particularly annotation data, are increasingly being represented in directed acyclic graphs (DAGs. However, while relevant biological information is implicit in the links between multiple domains, annotations from these different domains are usually represented in distinct, unconnected DAGs, making links between the domains represented difficult to determine. We develop a novel family of general statistical tests for the discovery of strong associations between two directed acyclic graphs. Our method takes the topology of the input graphs and the specificity and relevance of associations between nodes into consideration. We apply our method to the extraction of associations between biomedical ontologies in an extensive use-case. Through a manual and an automatic evaluation, we show that our tests discover biologically relevant relations. The suite of statistical tests we develop for this purpose is implemented and freely available for download.
Mean-squared-displacement statistical test for fractional Brownian motion
Sikora, Grzegorz; Burnecki, Krzysztof; Wyłomańska, Agnieszka
2017-03-01
Anomalous diffusion in crowded fluids, e.g., in cytoplasm of living cells, is a frequent phenomenon. A common tool by which the anomalous diffusion of a single particle can be classified is the time-averaged mean square displacement (TAMSD). A classical mechanism leading to the anomalous diffusion is the fractional Brownian motion (FBM). A validation of such process for single-particle tracking data is of great interest for experimentalists. In this paper we propose a rigorous statistical test for FBM based on TAMSD. To this end we analyze the distribution of the TAMSD statistic, which is given by the generalized chi-squared distribution. Next, we study the power of the test by means of Monte Carlo simulations. We show that the test is very sensitive for changes of the Hurst parameter. Moreover, it can easily distinguish between two models of subdiffusion: FBM and continuous-time random walk.
Fully Bayesian tests of neutrality using genealogical summary statistics
Drummond Alexei J
2008-10-01
Full Text Available Abstract Background Many data summary statistics have been developed to detect departures from neutral expectations of evolutionary models. However questions about the neutrality of the evolution of genetic loci within natural populations remain difficult to assess. One critical cause of this difficulty is that most methods for testing neutrality make simplifying assumptions simultaneously about the mutational model and the population size model. Consequentially, rejecting the null hypothesis of neutrality under these methods could result from violations of either or both assumptions, making interpretation troublesome. Results Here we harness posterior predictive simulation to exploit summary statistics of both the data and model parameters to test the goodness-of-fit of standard models of evolution. We apply the method to test the selective neutrality of molecular evolution in non-recombining gene genealogies and we demonstrate the utility of our method on four real data sets, identifying significant departures of neutrality in human influenza A virus, even after controlling for variation in population size. Conclusion Importantly, by employing a full model-based Bayesian analysis, our method separates the effects of demography from the effects of selection. The method also allows multiple summary statistics to be used in concert, thus potentially increasing sensitivity. Furthermore, our method remains useful in situations where analytical expectations and variances of summary statistics are not available. This aspect has great potential for the analysis of temporally spaced data, an expanding area previously ignored for limited availability of theory and methods.
Xu Ke
2007-06-01
Full Text Available Abstract Background Tests for association between a haplotype and disease are commonly performed using a likelihood ratio test for heterogeneity between case and control haplotype frequencies. Using data from a study of association between heroin dependence and the DRD2 gene, we obtained estimated haplotype frequencies and the associated likelihood ratio statistic using two different computer programs, MLOCUS and GENECOUNTING. We also carried out permutation testing to assess the empirical significance of the results obtained. Results Both programs yielded similar, though not identical, estimates for the haplotype frequencies. MLOCUS produced a p value of 1.8*10-15 and GENECOUNTING produced a p value of 5.4*10-4. Permutation testing produced a p value 2.8*10-4. Conclusion The fact that very large differences occur between the likelihood ratio statistics from the two programs may reflect the fact that the haplotype frequencies for the combined group are not constrained to be equal to the weighted averages of the frequencies for the cases and controls, as they would be if they were directly observed rather than being estimated. Minor differences in haplotype frequency estimates can result in very large differences in the likelihood ratio statistic and associated p value.
Your Chi-Square Test Is Statistically Significant: Now What?
Donald Sharpe
2015-04-01
Full Text Available 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 from two recent journal articles were used to illustrate these approaches. A call is made for greater consideration of foundational techniques such as the chi-square tests.
Asymptotics of Bonferroni for Dependent Normal Test Statistics.
Proschan, Michael A; Shaw, Pamela A
2011-07-01
The Bonferroni adjustment is sometimes used to control the familywise error rate (FWE) when the number of comparisons is huge. In genome wide association studies, researchers compare cases to controls with respect to thousands of single nucleotide polymorphisms. It has been claimed that the Bonferroni adjustment is only slightly conservative if the comparisons are nearly independent. We show that the veracity of this claim depends on how one defines "nearly." Specifically, if the test statistics' pairwise correlations converge to 0 as the number of tests tend to ∞, the conservatism of the Bonferroni procedure depends on their rate of convergence. The type I error rate of Bonferroni can tend to 0 or 1 - exp(-α) ≈ α, depending on that rate. We show using elementary probability theory what happens to the distribution of the number of errors when using Bonferroni, as the number of dependent normal test statistics gets large. We also use the limiting behavior of Bonferroni to shed light on properties of other commonly used test statistics.
Statistical testing and distribution for lead chloride toxicity
John H. Lange
2005-01-01
@@ Dear Sir, Graca et al. [1] provided an interesting investigation on the toxicity of lead chloride and sperm development in mice. However, I would like to make a comment on the statistical analysis presented. Table 1 and its results suggest that a comparison of treated (experiment) and control mice were undertaken using the t-test. The authors indicate that they used the t-test along with complementation of ANOVA analysis. It appears that the t-test was used for analysis in Table 1 and ANOVA, as indicated,for Table 2. Use of t-test for comparing three of more groups is not appropriate since this may result in a multiple comparison problem (increasing the type I error rate)[2, 3]. Multiple comparisons can result in the reporting of a P value that is significant (or of lower value) when in actuality it is not. It is better to use, for example, a one-way ANOVA followed by a post-test (post-hoc)which can take into account all comparisons. Other statistical testing can also be employed to control the overall type I error, such as Tukey-HSD (honest significant difference), Scheffe's and Bonferroni-Dunn methods [2].
Using Relative Statistics and Approximate Disease Prevalence to Compare Screening Tests.
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.
Testing the rate isomorphy hypothesis using five statistical methods
Xian-Ju Kuang; Megha N. Parajulee2+,; Pei-Jian Shi; Feng Ge; Fang-Sen Xue
2012-01-01
Organisms are said to be in developmental rate isomorphy when the proportions of developmental stage durations are unaffected by temperature.Comprehensive stage-specific developmental data were generated on the cabbage beetle,Colaphellus bowringi Baly (Coleoptera:Chrysomelidae),at eight temperatures ranging from 16℃ to 30℃ (in 2℃ increments) and five analytical methods were used to test the rate isomorphy hypothesis,including:(i) direct comparison of lower developmental thresholds with standard errors based on the traditional linear equation describing developmental rate as the linear function of temperature; (ii) analysis of covariance to compare the lower developmental thresholds of different stages based on the Ikemoto-Takai linear equation; (iii)testing the significance of the slope item in the regression line of arcsin(√P) versus temperature,where p is the ratio of the developmental duration of a particular developmental stage to the entire pre-imaginal developmental duration for one insect or mite species; (iv)analysis of variance to test for significant differences between the ratios of developmental stage durations to that of pre-imaginal development; and (v) checking whether there is an element less than a given level of significance in the p-value matrix of rotating regression line.The results revealed no significant difference among the lower developmental thresholds or among the aforementioned ratios,and thus convincingly confirmed the rate isomorphy hypothesis.
Shaikh, Masood Ali
2016-04-01
Statistical tests help infer meaningful conclusions from studies conducted and data collected. This descriptive study analyzed the type of statistical tests used and the statistical software utilized for analysis reported in the original articles published in 2014 by the three Medline-indexed journals of Pakistan. Cumulatively, 466 original articles were published in 2014. The most frequently reported statistical tests for original articles by all three journals were bivariate parametric and non-parametric tests i.e. involving comparisons between two groups e.g. Chi-square test, t-test, and various types of correlations. Cumulatively, 201 (43.1%) articles used these tests. SPSS was the primary choice for statistical analysis, as it was exclusively used in 374 (80.3%) original articles. There has been a substantial increase in the number of articles published, and in the sophistication of statistical tests used in the articles published in the Pakistani Medline indexed journals in 2014, compared to 2007.
Probability and Statistics Questions and Tests : a critical analysis
Fabrizio Maturo
2015-06-01
Full Text Available In probability and statistics courses, a popular method for the evaluation of the students is to assess them using multiple choice tests. The use of these tests allows to evaluate certain types of skills such as fast response, short-term memory, mental clarity and ability to compete. In our opinion, the verification through testing can certainly be useful for the analysis of certain aspects, and to speed up the process of assessment, but we should be aware of the limitations of such a standardized procedure and then exclude that the assessments of pupils, classes and schools can be reduced to processing of test results. To prove this thesis, this article argues in detail the main test limits, presents some recent models which have been proposed in the literature and suggests some alternative valuation methods. Quesiti e test di Probabilità e Statistica: un'analisi critica Nei corsi di Probabilità e Statistica, un metodo molto diffuso per la valutazione degli studenti consiste nel sottoporli a quiz a risposta multipla. L'uso di questi test permette di valutare alcuni tipi di abilità come la rapidità di risposta, la memoria a breve termine, la lucidità mentale e l'attitudine a gareggiare. A nostro parere, la verifica attraverso i test può essere sicuramente utile per l'analisi di alcuni aspetti e per velocizzare il percorso di valutazione ma si deve essere consapevoli dei limiti di una tale procedura standardizzata e quindi escludere che le valutazioni di alunni, classi e scuole possano essere ridotte a elaborazioni di risultati di test. A dimostrazione di questa tesi, questo articolo argomenta in dettaglio i limiti principali dei test, presenta alcuni recenti modelli proposti in letteratura e propone alcuni metodi di valutazione alternativi. Parole Chiave: item responce theory, valutazione, test, probabilità
Surrogate/spent fuel sabotage : aerosol ratio test program and Phase 2 test results.
Borek, Theodore Thaddeus III; Thompson, N. Slater (U.S. Department of Energy); Sorenson, Ken Bryce; Hibbs, R.S. (U.S. Department of Energy); Nolte, Oliver (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Molecke, Martin Alan; Autrusson, Bruno (Institut de Radioprotection et de Surete Nucleaire, France); Young, F. I. (U.S. Nuclear Regulatory Commission); Koch, Wolfgang (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Brochard, Didier (Institut de Radioprotection et de Surete Nucleaire, France); Pretzsch, Gunter Guido (Gesellschaft fur Anlagen- und Reaktorsicherheit, Germany); Lange, Florentin (Gesellschaft fur Anlagen- und Reaktorsicherheit, Germany)
2004-05-01
A multinational test program is in progress to quantify the aerosol particulates produced when a high energy density device, HEDD, impacts surrogate material and actual spent fuel test rodlets. This program provides needed data that are relevant to some sabotage scenarios in relation to spent fuel transport and storage casks, and associated risk assessments; the program also provides significant political benefits in international cooperation. We are quantifying the spent fuel ratio, SFR, the ratio of the aerosol particles released from HEDD-impacted actual spent fuel to the aerosol particles produced from surrogate materials, measured under closely matched test conditions. In addition, we are measuring the amounts, nuclide content, size distribution of the released aerosol materials, and enhanced sorption of volatile fission product nuclides onto specific aerosol particle size fractions. These data are crucial for predicting radiological impacts. This document includes a thorough description of the test program, including the current, detailed test plan, concept and design, plus a description of all test components, and requirements for future components and related nuclear facility needs. It also serves as a program status report as of the end of FY 2003. All available test results, observations, and analyses - primarily for surrogate material Phase 2 tests using cerium oxide sintered ceramic pellets are included. This spent fuel sabotage - aerosol test program is coordinated with the international Working Group for Sabotage Concerns of Transport and Storage Casks, WGSTSC, and supported by both the U.S. Department of Energy and Nuclear Regulatory Commission.
A statistical analysis of the effect of warfare on the human secondary sex ratio
Graffelman, J.; Hoekstra, R.F.
2000-01-01
Many factors have been hypothesized to affect the human secondary sex ratio (the annual percentage of males among all live births), among them race, parental ages, and birth order. Some authors have even proposed warfare as a factor influencing live birth sex ratios. The hypothesis that during and s
Teyssèdre Simon
2012-11-01
Full Text Available Abstract Background Spurious associations between single nucleotide polymorphisms and phenotypes are a major issue in genome-wide association studies and have led to underestimation of type 1 error rate and overestimation of the number of quantitative trait loci found. Many authors have investigated the influence of population structure on the robustness of methods by simulation. This paper is aimed at developing further the algebraic formalization of power and type 1 error rate for some of the classical statistical methods used: simple regression, two approximate methods of mixed models involving the effect of a single nucleotide polymorphism (SNP and a random polygenic effect (GRAMMAR and FASTA and the transmission/disequilibrium test for quantitative traits and nuclear families. Analytical formulae were derived using matrix algebra for the first and second moments of the statistical tests, assuming a true mixed model with a polygenic effect and SNP effects. Results The expectation and variance of the test statistics and their marginal expectations and variances according to the distribution of genotypes and estimators of variance components are given as a function of the relationship matrix and of the heritability of the polygenic effect. These formulae were used to compute type 1 error rate and power for any kind of relationship matrix between phenotyped and genotyped individuals for any level of heritability. For the regression method, type 1 error rate increased with the variability of relationships and with heritability, but decreased with the GRAMMAR method and was not affected with the FASTA and quantitative transmission/disequilibrium test methods. Conclusions The formulae can be easily used to provide the correct threshold of type 1 error rate and to calculate the power when designing experiments or data collection protocols. The results concerning the efficacy of each method agree with simulation results in the literature but were
Quantum Statistical Testing of a Quantum Random Number Generator
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.
Quantum Statistical Testing of a Quantum Random Number Generator
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.
Quantum statistical testing of a quantum random number generator
Humble, Travis S.
2014-10-01
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 operation 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.
Statistical tests for power-law cross-correlated processes.
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, ρ(DCCA)(T,n), where T is the total length of the time series and n the window size. For ρ(DCCA)(T,n), we numerically calculated the Cauchy inequality -1 ≤ ρ(DCCA)(T,n) ≤ 1. Here we derive -1 ≤ ρ DCCA)(T,n) ≤ 1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρ(DCCA) 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 ρ(DCCA)(T,n) tends with increasing T to 1/T. Using ρ(DCCA)(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.
Measures of effect size for chi-squared and likelihood-ratio goodness-of-fit tests.
Johnston, Janis E; Berry, Kenneth J; Mielke, Paul W
2006-10-01
A fundamental shift in editorial policy for psychological journals was initiated when the fourth edition of the Publication Manual of the American Psychological Association (1994) placed emphasis on reporting measures of effect size. This paper presents measures of effect size for the chi-squared and the likelihood-ratio goodness-of-fit statistic tests.
Modified likelihood ratio test for homogeneity in normal mixtures with two samples
QIN Yong-song; LEI Qing-zhu
2008-01-01
This paper investigates the modified likelihood ratio test(LRT) for homogeneity in normal mixtures of two samples with mixing proportions unknown. It is proved that the limit distribution of the modified likelihood ratio test is X2(1).
Pearce element ratios: A paradigm for testing hypotheses
Russell, J. K.; Nicholls, Jim; Stanley, Clifford R.; Pearce, T. H.
Science moves forward with the development of new ideas that are encapsulated by hypotheses whose aim is to explain the structure of data sets or to expand existing theory. These hypotheses remain conjecture until they have been tested. In fact, Karl Popper advocated that a scientist's job does not finish with the creation of an idea but, rather, begins with the testing of the related hypotheses. In Popper's [1959] advocation it is implicit that there be tools with which we can test our hypotheses. Consequently, the development of rigorous tests for conceptual models plays a major role in maintaining the integrity of scientific endeavor [e.g., Greenwood, 1989].
Nearly Efficient Likelihood Ratio Tests for Seasonal Unit Roots
Jansson, Michael; Nielsen, Morten Ørregaard
that these tests are "nearly efficient" in the sense of Elliott, Rothenberg, and Stock (1996), i.e. that their local asymptotic power functions are indistinguishable from the Gaussian power envelope. Currently available nearly efficient testing procedures for seasonal unit roots are regression-based and require...
21 CFR 862.1455 - Lecithin/sphingomyelin ratio in amniotic fluid test system.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Lecithin/sphingomyelin ratio in amniotic fluid... Clinical Chemistry Test Systems § 862.1455 Lecithin/sphingomyelin ratio in amniotic fluid test system. (a) Identification. A lecithin/sphingomyelin ratio in amniotic fluid test system is a device intended to measure the...
Improved anomaly detection using multi-scale PLS and generalized likelihood ratio test
Madakyaru, Muddu
2017-02-16
Process monitoring has a central role in the process industry to enhance productivity, efficiency, and safety, and to avoid expensive maintenance. In this paper, a statistical approach that exploit the advantages of multiscale PLS models (MSPLS) and those of a generalized likelihood ratio (GLR) test to better detect anomalies is proposed. Specifically, to consider the multivariate and multi-scale nature of process dynamics, a MSPLS algorithm combining PLS and wavelet analysis is used as modeling framework. Then, GLR hypothesis testing is applied using the uncorrelated residuals obtained from MSPLS model to improve the anomaly detection abilities of these latent variable based fault detection methods even further. Applications to a simulated distillation column data are used to evaluate the proposed MSPLS-GLR algorithm.
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...
Testing Result Statistics-Based Rapid Testing Method for Safety-Critical System
Zhi-Yao Deng; Nan Sang
2008-01-01
Safety-critical system (SCS) has highly demand for dependability, which requires plenty of resource to ensure that the system under test (SUT) satisfies the dependability requirement. In this paper, a new SCS rapid testing method is proposed to improve SCS adaptive dependability testing. The result of each test execution is saved in calculation memory unit and evaluated as an algorithm model. Then the least quantity of scenario test case for next test execution will be calculated according to the promised SUT's confidence level. The feedback data are generated to weight controller as the guideline for the further testing. Finally, a compre- hensive experiment study demonstrates that this adaptive testing method can really work in practice. This rapid testing method, testing result statistics-based adaptive control, makes the SCS dependability testing much more effective.
Comparison of Statistical Methods for Detector Testing Programs
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.
A test statistic for the affected-sib-set method.
Lange, K
1986-07-01
This paper discusses generalizations of the affected-sib-pair method. First, the requirement that sib identity-by-descent relations be known unambiguously is relaxed by substituting sib identity-by-state relations. This permits affected sibs to be used even when their parents are unavailable for typing. In the limit of an infinite number of marker alleles each of infinitesimal population frequency, the identity-by-state relations coincide with the usual identity-by-descent relations. Second, a weighted pairs test statistic is proposed that covers affected sib sets of size greater than two. These generalizations make the affected-sib-pair method a more powerful technique for detecting departures from independent segregation of disease and marker phenotypes. A sample calculation suggests such a departure for tuberculoid leprosy and the HLA D locus.
New, high statistics measurement of the K+ -> pi0 e+ nu (Ke3) branching ratio
Sher, A E; Atoyan, G S; Bassalleck, B; Bergman, D R; Cheung, N; Dhawan, S; Do, H; Egger, J; Eilerts, S W; Fischer, H; Herold, W D; Issakov, V V; Kaspar, H; Kraus, D E; Lazarus, D M; Lichard, P; Lowe, J; Lozano-Bahilo, J; Ma, H; Majid, W A; Pislak, S; Poblaguev, A A; Rehak, P; Sher, A E; Thompson, J A; Truöl, P; Zeller, M E; Sher, Aleksey
2003-01-01
E865 at the Brookhaven National Laboratory AGS collected about 70,000 K+(e3) events with the purpose of measuring the relative K+(e3) branching ratio. The pi0 in all the decays was detected using the e+e- pair from pi0 -> e+e-gamma decay and no photons were required. Using the Particle Data Group branching ratios for the normalization decays we obtain BR(K+(e3(gamma))=(5.13+/-0.02(stat)+/-0.09(sys)+/-0.04(norm))%, where $K+(e3(gamma)) includes the effect of virtual and real photons. This result is 2.3 sigma higher than the current Particle Data Group value. The implications of this result for the $V_{us}$ element of the CKM matrix, and the matrix's unitarity are discussed.
ALTMANN, BERTHOLD
AFTER A BRIEF SUMMARY OF THE TEST PROGRAM (DESCRIBED MORE FULLY IN LI 000 318), THE STATISTICAL RESULTS TABULATED AS OVERALL "ABC (APPROACH BY CONCEPT)-RELEVANCE RATIOS" AND "ABC-RECALL FIGURES" ARE PRESENTED AND REVIEWED. AN ABSTRACT MODEL DEVELOPED IN ACCORDANCE WITH MAX WEBER'S "IDEALTYPUS" ("DIE OBJEKTIVITAET SOZIALWISSENSCHAFTLICHER UND…
A Multiuser MIMO Transmit Beamformer Based on the Statistics of the Signal-to-Leakage Ratio
Chalise BatuK
2009-01-01
Full Text Available A multiuser multiple-input multiple-output (MIMO downlink communication system is analyzed in a Rayleigh fading environment. The approximate closed-form expressions for the probability density function (PDF of the signal-to-leakage ratio (SLR, its average, and the outage probability have been derived in terms of the transmit beamformer weight vector. With the help of some conservative derivations, it has been shown that the transmit beamformer which maximizes the average SLR also minimizes the outage probability of the SLR. Computer simulations are carried out to compare the theoretical and simulation results for the channels whose spatial correlations are modeled with different methods.
Yuan, Ke-Hai
2008-01-01
In the literature of mean and covariance structure analysis, noncentral chi-square distribution is commonly used to describe the behavior of the likelihood ratio (LR) statistic under alternative hypothesis. Due to the inaccessibility of the rather technical literature for the distribution of the LR statistic, it is widely believed that the noncentral chi-square distribution is justified by statistical theory. Actually, when the null hypothesis is not trivially violated, the noncentral chi-square distribution cannot describe the LR statistic well even when data are normally distributed and the sample size is large. Using the one-dimensional case, this article provides the details showing that the LR statistic asymptotically follows a normal distribution, which also leads to an asymptotically correct confidence interval for the discrepancy between the null hypothesis/model and the population. For each one-dimensional result, the corresponding results in the higher dimensional case are pointed out and references are provided. Examples with real data illustrate the difference between the noncentral chi-square distribution and the normal distribution. Monte Carlo results compare the strength of the normal distribution against that of the noncentral chi-square distribution. The implication to data analysis is discussed whenever relevant. The development is built upon the concepts of basic calculous, linear algebra, and introductory probability and statistics. The aim is to provide the least technical material for quantitative graduate students in social science to understand the condition and limitation of the noncentral chi-square distribution.
A statistical design for testing apomictic diversification through linkage analysis.
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.
F-Ratio Test and Hypothesis Weighting: A Methodology to Optimize Feature Vector Size
R. M. Dünki
2011-01-01
Full Text Available Reducing a feature vector to an optimized dimensionality is a common problem in biomedical signal analysis. This analysis retrieves the characteristics of the time series and its associated measures with an adequate methodology followed by an appropriate statistical assessment of these measures (e.g., spectral power or fractal dimension. As a step towards such a statistical assessment, we present a data resampling approach. The techniques allow estimating σ2(F, that is, the variance of an F-value from variance analysis. Three test statistics are derived from the so-called F-ratio σ2(F/F2. A Bayesian formalism assigns weights to hypotheses and their corresponding measures considered (hypothesis weighting. This leads to complete, partial, or noninclusion of these measures into an optimized feature vector. We thus distinguished the EEG of healthy probands from the EEG of patients diagnosed as schizophrenic. A reliable discriminance performance of 81% based on Taken's χ, α-, and δ-power was found.
Development and testing of improved statistical wind power forecasting methods.
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
Testing Result Statistics-Based Rapid Testing Method for Safety-Critical System
Zhi-Yao Deng; Nan Sang
2008-01-01
Safety-critical system (SCS) has highlydemand for dependability, which requires plenty ofresource to ensure that the system under test (SUT)satisfies the dependability requirement. In this paper, anew SCS rapid testing method is proposed to improveSCS adaptive dependability testing. The result of each testexecution is saved in calculation memory unit andevaluated as an algorithm model. Then the least quantityof scenario test case for next test execution will becalculated according to the promised SUT's confidencelevel. The feedback data are generated to weightcontroller as the guideline for the further testing. Finally,a compre- hensive experiment study demonstrates thatthis adaptive testing method can really work in practice.This rapid testing method, testing result statistics-basedadaptive control, makes the SCS dependability testingmuch more effective.
An Orthogonal Test of the $L$-functions Ratios Conjecture, II
Miller, Steven J
2009-01-01
Recently Conrey, Farmer, and Zirnbauer developed the L-functions Ratios conjecture, which gives a recipe that predicts a wealth of statistics, from moments to spacings between adjacent zeros and values of L-functions. The problem with this method is that several of its steps involve ignoring error terms of size comparable to the main term; amazingly, the errors seem to cancel and the resulting prediction is expected to be accurate up to square-root cancellation. We prove the accuracy of the Ratios Conjecture's prediction for the 1-level density of families of cuspidal newforms of constant sign (up to square-root agreement for support in (-1,1), and up to a power savings in (-2,2)), and discuss the arithmetic significance of the lower order terms. This is the most involved test of the Ratios Conjecture's predictions to date, as it is known that the error terms dropped in some of the steps do not cancel, but rather contribute a main term! Specifically, these are the non-diagonal terms in the Petersson formula, ...
Palhol, Fabien; Lamoureux, Catherine; Chabrillat, Martine; Naulet, Norbert
2004-05-10
In this study, the {sup 15}N/{sup 14}N isotopic ratios of 106 samples of 3,4-methylenedioxymethamphetamine (MDMA) extracted from Ecstasy tablets are presented. These ratios, measured using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS), show a large discrimination between samples with a range of {delta}{sup 15}N values between -17 and +19%o, depending on the precursors and the method used in clandestine laboratories. Thus, {delta}{sup 15}N values can be used in a statistical analysis carried out in order to link Ecstasy tablets prepared with the same precursors and synthetic pathway. The similarity index obtained after principal component analysis and hierarchical cluster analysis appears to be an efficient way to group tablets seized in different places.
The dJ/dS Ratio Test Reveals Hundreds of Novel Putative Cancer Drivers.
Chen, Han; Xing, Ke; He, Xionglei
2015-08-01
Computational tools with a balanced sensitivity and specificity in identification of candidate cancer drivers are highly desired. In this study, we propose a new statistical test, namely the dJ/dS ratio test, to compute the relative mutation rate of exon/intron junction sites (dJ) to synonymous sites (dS); observation of dJ/dS ratio larger than 1 in cancer indicates positive selection for splicing deregulation, a signature of cancer driver genes. Using this method, we analyzed the data from The Cancer Genome Atlas and identified hundreds of novel putative cancer drivers. Interestingly, these genes are highly enriched in biological processes related to the development and maintenance of multicellularity, paralleling a previous finding that cancer evolves back to be unicellular by knocking down the multicellularity-associated genetic network. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
New Statistical PDFs: Predictions and Tests up to LHC Energies
Soffer, Jacques
2016-01-01
The quantum statistical parton distributions approach proposed more than one decade ago is revisited by considering a larger set of recent and accurate Deep Inelastic Scattering experimental results. It enables us to improve the description of the data by means of a new determination of the parton distributions. This global next-to-leading order QCD analysis leads to a good description of several structure functions, involving unpolarized parton distributions and helicity distributions, in a broad range of $x$ and $Q^2$ and in terms of a rather small number of free parameters. There are several challenging issues, in particular the behavior of $\\bar d(x) / \\bar u(x)$ at large $x$, a possible large positive gluon helicity distribution, etc.. The predictions of this theoretical approach will be tested for single-jet production and charge asymmetry in $W^{\\pm}$ production in $\\bar p p$ and $p p$ collisions up to LHC energies, using recent data and also for forthcoming experimental results.
Statistical tools for weld defect evaluation in radiographic testing
Nacereddine, N.; Tridi, M. [LTSI, Centre de Recherche en Soudage et Controle, Alger (Algeria); Hamami, L. [Ecole National Polytechnique, Alger (Algeria). Dept. Electronique; Ziou, D. [Sherbrooke Univ., Quebec (Canada). DMI, Faculte des Sciences
2006-07-01
A reliable detection of defects in welded joints is one of the most important tasks in non-destructive testing by radiography, since the human factor still has a decisive influence on the evaluation of defects on the film. An incorrect classification may disapprove a piece in good conditions or approve a piece with discontinuities exceeding the limit established by the applicable standards. The progresses in computer science and the artificial intelligence techniques have allowed the welded joint quality interpretation to be carried out by using pattern recognition tools, making the system of the weld inspection more reliable, reproducible and faster. In this work, we develop and implement algorithms based on statistical approaches for segmentation and classification of the weld defects. Because of the complex nature of the considered images and so that the extracted defect area represents the most accurately possible the real defect, and that the detected defect corresponds as well as possible to its real class, the choice of the algorithms must be very judicious. In order to achieve this, a comparative study of the various segmentation and classification methods was performed to demonstrate the advantages of the ones in comparison with the others giving to the most optimal combinations. (orig.)
30 CFR 7.87 - Test to determine the maximum fuel-air ratio.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Test to determine the maximum fuel-air ratio. 7... Use in Underground Coal Mines § 7.87 Test to determine the maximum fuel-air ratio. (a) Test procedure... several speed/torque conditions to determine the concentrations of CO and NOX, dry basis, in the...
McGraw, R. L.; Luke, E. P.; Kollias, P.
2014-12-01
We develop methods that determine the influence of turbulence on the distribution of in-cloud water vapor saturation ratio and growth rates of cloud droplets. For this purpose, a moment-based cloud parcel model is used to translate Doppler cloud radar vertical velocity spectra and radiosonde measurements into a statistical distribution of in-cloud saturation ratio, S. Because cloud droplet growth/evaporation rates are proportional to S-1, the statistical analysis of fluctuations in S yields, among other quantities, direct information on the time correlation function of droplet growth rate. From this information a Green-Kubo relation is used to determine the diffusion coefficient for fluctuations along the coordinate of cloud droplet size, D, a key turbulence parameter used in the kinetic potential theory of drizzle formation. Measurements from the Azores, SGP, and TCAP sites are analyzed and compared. A significant finding is that the probability distribution function for fluctuations in S tends to be both highly symmetric about the equilibrium saturation ratio (S=1) and non-Gaussian. Indeed the distribution has much broader tails than the Gaussian and, for the cases we have studied, turns out to be in excellent agreement with the Voight lineshape.
Statistical tests for taxonomic distinctiveness from observations of monophyly.
Rosenberg, Noah A
2007-02-01
The observation of monophyly for a specified set of genealogical lineages is often used to place the lineages into a distinctive taxonomic entity. However, it is sometimes possible that monophyly of the lineages can occur by chance as an outcome of the random branching of lineages within a single taxon. Thus, especially for small samples, an observation of monophyly for a set of lineages--even if strongly supported statistically--does not necessarily indicate that the lineages are from a distinctive group. Here I develop a test of the null hypothesis that monophyly is a chance outcome of random branching. I also compute the sample size required so that the probability of chance occurrence of monophyly of a specified set of lineages lies below a prescribed tolerance. Under the null model of random branching, the probability that monophyly of the lineages in an index group occurs by chance is substantial if the sample is highly asymmetric, that is, if only a few of the sampled lineages are from the index group, or if only a few lineages are external to the group. If sample sizes are similar inside and outside the group of interest, however, chance occurrence of monophyly can be rejected at stringent significance levels (P < 10(-5)) even for quite small samples (approximately 20 total lineages). For a fixed total sample size, rejection of the null hypothesis of random branching in a single taxon occurs at the most stringent level if samples of nearly equal size inside and outside the index group--with a slightly greater size within the index group--are used. Similar results apply, with smaller sample sizes needed, when reciprocal monophyly of two groups, rather than monophyly of a single group, is of interest. The results suggest minimal sample sizes required for inferences to be made about taxonomic distinctiveness from observations of monophyly.
Li, Xiaochun; Li, Huilin; Jin, Man; D Goldberg, Judith
2016-09-10
We consider the non-inferiority (or equivalence) test of the odds ratio (OR) in a crossover study with binary outcomes to evaluate the treatment effects of two drugs. To solve this problem, Lui and Chang (2011) proposed both an asymptotic method and a conditional method based on a random effects logit model. Kenward and Jones (1987) proposed a likelihood ratio test (LRTM ) based on a log linear model. These existing methods are all subject to model misspecification. In this paper, we propose a likelihood ratio test (LRT) and a score test that are independent of model specification. Monte Carlo simulation studies show that, in scenarios considered in this paper, both the LRT and the score test have higher power than the asymptotic and conditional methods for the non-inferiority test; the LRT, score, and asymptotic methods have similar power, and they all have higher power than the conditional method for the equivalence test. When data can be well described by a log linear model, the LRTM has the highest power among all the five methods (LRTM , LRT, score, asymptotic, and conditional) for both non-inferiority and equivalence tests. However, in scenarios for which a log linear model does not describe the data well, the LRTM has the lowest power for the non-inferiority test and has inflated type I error rates for the equivalence test. We provide an example from a clinical trial that illustrates our methods. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
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.
On Statistics of Log-Ratio of Arithmetic Mean to Geometric Mean for Nakagami-m Fading Power
Wang, Ning; Cheng, Julian; Tellambura, Chintha
To assess the performance of maximum-likelihood (ML) based Nakagami m parameter estimators, current methods rely on Monte Carlo simulation. In order to enable the analytical performance evaluation of ML-based m parameter estimators, we study the statistical properties of a parameter Δ, which is defined as the log-ratio of the arithmetic mean to the geometric mean for Nakagami-m fading power. Closed-form expressions are derived for the probability density function (PDF) of Δ. It is found that for large sample size, the PDF of Δ can be well approximated by a two-parameter Gamma PDF.
STATISTICAL ANALYSIS OF SOME EXPERIMENTAL FATIGUE TESTS RESULTS
Adrian Stere PARIS; Gheorghe AMZA; Claudiu BABIŞ; Dan Niţoi
2012-01-01
The paper details the results of processing the fatigue data experiments to find the regression function. Application software for statistical processing like ANOVA and regression calculi are properly utilized, with emphasis on popular software like MSExcel and CurveExpert
TESTS OF ELLIPTICAL SYMMETRY AND THE ASYMPTOTIC TAIL BEHAVIOR OF THE STATISTICS
JingPing; ZhuLixing
1999-01-01
In this paper, some test statistics Of Kolmogorov type and Cramervon Mises type based on projection pursuit technique are proposed for testing the sphericity problem of a high-dimensional distribution. The limiting distributions of the test statistics are derived under the null hypothesis. The asymptotic properties of Bootstrap approximation are investigated and the tail behaviors of the statistics are studied.
Association studies with imputed variants using expectation-maximization likelihood-ratio tests.
Kuan-Chieh Huang
Full Text Available Genotype imputation has become standard practice in modern genetic studies. As sequencing-based reference panels continue to grow, increasingly more markers are being well or better imputed but at the same time, even more markers with relatively low minor allele frequency are being imputed with low imputation quality. Here, we propose new methods that incorporate imputation uncertainty for downstream association analysis, with improved power and/or computational efficiency. We consider two scenarios: I when posterior probabilities of all potential genotypes are estimated; and II when only the one-dimensional summary statistic, imputed dosage, is available. For scenario I, we have developed an expectation-maximization likelihood-ratio test for association based on posterior probabilities. When only imputed dosages are available (scenario II, we first sample the genotype probabilities from its posterior distribution given the dosages, and then apply the EM-LRT on the sampled probabilities. Our simulations show that type I error of the proposed EM-LRT methods under both scenarios are protected. Compared with existing methods, EM-LRT-Prob (for scenario I offers optimal statistical power across a wide spectrum of MAF and imputation quality. EM-LRT-Dose (for scenario II achieves a similar level of statistical power as EM-LRT-Prob and, outperforms the standard Dosage method, especially for markers with relatively low MAF or imputation quality. Applications to two real data sets, the Cebu Longitudinal Health and Nutrition Survey study and the Women's Health Initiative Study, provide further support to the validity and efficiency of our proposed methods.
STATISTICAL ANALYSIS OF SOME EXPERIMENTAL FATIGUE TESTS RESULTS
Adrian Stere PARIS
2012-05-01
Full Text Available The paper details the results of processing the fatigue data experiments to find the regression function. Application software for statistical processing like ANOVA and regression calculi are properly utilized, with emphasis on popular software like MSExcel and CurveExpert
Understanding the Sampling Distribution and Its Use in Testing Statistical Significance.
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…
Reply to 'Statistical testing and distribution for lead chloride toxicity'
Maria de Lourdes Pereira; J. Ramalho-Santos
2005-01-01
@@ Dear Sir, We are very grateful for the letter written by Dr Lange,and indeed apologize for the mistakes noted in the wording of our text regarding statistical analysis. This was due to changes carried out while revising the manuscript at the request of reviewers, whom we thank for, pointing out several issues that were actually similar to those noted by Dr. Lange. Unfortunately, we were unable to
Drug-excipient compatibility testing using a high-throughput approach and statistical design.
Wyttenbach, Nicole; Birringer, Christian; Alsenz, Jochem; Kuentz, Martin
2005-01-01
The aim of our research was to develop a miniaturized high throughput drug-excipient compatibility test. Experiments were planned and evaluated using statistical experimental design. Binary mixtures of a drug, acetylsalicylic acid, or fluoxetine hydrochloride, and of excipients commonly used in solid dosage forms were prepared at a ratio of approximately 1:100 in 96-well microtiter plates. Samples were exposed to different temperature (40 degrees C/ 50 degrees C) and humidity (10%/75%) for different time (1 week/4 weeks), and chemical drug degradation was analyzed using a fast gradient high pressure liquid chromatography (HPLC). Categorical statistical design was applied to identify the effects and interactions of time, temperature, humidity, and excipient on drug degradation. Acetylsalicylic acid was least stable in the presence of magnesium stearate, dibasic calcium phosphate, or sodium starch glycolate. Fluoxetine hydrochloride exhibited a marked degradation only with lactose. Factor-interaction plots revealed that the relative humidity had the strongest effect on the drug excipient blends tested. In conclusion, the developed technique enables fast drug-excipient compatibility testing and identification of interactions. Since only 0.1 mg of drug is needed per data point, fast rational preselection of the pharmaceutical additives can be performed early in solid dosage form development.
Statistical Analysis for Test Papers with Software SPSS
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.
A semiparametric Wald statistic for testing logistic regression models based on case-control data
2008-01-01
We propose a semiparametric Wald statistic to test the validity of logistic regression models based on case-control data. The test statistic is constructed using a semiparametric ROC curve estimator and a nonparametric ROC curve estimator. The statistic has an asymptotic chi-squared distribution and is an alternative to the Kolmogorov-Smirnov-type statistic proposed by Qin and Zhang in 1997, the chi-squared-type statistic proposed by Zhang in 1999 and the information matrix test statistic proposed by Zhang in 2001. The statistic is easy to compute in the sense that it requires none of the following methods: using a bootstrap method to find its critical values, partitioning the sample data or inverting a high-dimensional matrix. We present some results on simulation and on analysis of two real examples. Moreover, we discuss how to extend our statistic to a family of statistics and how to construct its Kolmogorov-Smirnov counterpart.
Statistics of sampling for microbiological testing of foodborne pathogens
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...
Kotliar, K E; Lanzl, I M
2016-10-01
The use and the understanding of statistics are very important for biomedical research and for the clinical practice. This is particularly true for estimation of the possibilities for different diagnostic and therapy options in the field of glaucoma. The apparent complexity and contraintuitiveness of statistics along with a cautious acceptance by many physicians, might be the cause of conscious and unconscious manipulation with data representation and interpretation. Comprehendable clarification of some typical errors in the handling of medical statistical data. Using two hypothetical examples from glaucoma diagnostics the presentation of the effect of a hypotensive drug and interpretation of the results of a diagnostic test and typical statistical applications and sources of error are analyzed in detail and discussed. Mechanisms of data manipulation and incorrect data interpretation are elucidated. Typical sources of error in the statistical analysis and data presentation are explained. The practical examples analyzed demonstrate the need to understand the basics of statistics and to be able to apply them correctly. The lack of basic knowledge or half-knowledge in medical statistics can lead to misunderstandings, confusion and wrong decisions in medical research and also in clinical practice.
Choosing statistical tests: part 12 of a series on evaluation of scientific publications.
du Prel, Jean-Baptist; Röhrig, Bernd; Hommel, Gerhard; Blettner, Maria
2010-05-01
The interpretation of scientific articles often requires an understanding of the methods of inferential statistics. This article informs the reader about frequently used statistical tests and their correct application. The most commonly used statistical tests were identified through a selective literature search on the methodology of medical research publications. These tests are discussed in this article, along with a selection of other standard methods of inferential statistics. Readers who are acquainted not just with descriptive methods, but also with Pearson's chi-square test, Fisher's exact test, and Student's t test will be able to interpret a large proportion of medical research articles. Criteria are presented for choosing the proper statistical test to be used out of the most frequently applied tests. An algorithm and a table are provided to facilitate the selection of the appropriate test.
A statistical test on the reliability of the non-coevality of stars in binary systems
Valle, G; Moroni, P G Prada; Degl'Innocenti, S
2016-01-01
We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] Msun, and on stars in the main-sequence phase. The ages were obtained by means of the maximum-likelihood SCEPtER technique. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected. The median expected difference in the reconstructed age between the coeval stars of a binary system -- caused alone by the observational uncertainties -- shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near Z...
Improved likelihood ratio tests for cointegration rank in the VAR model
Boswijk, H.P.; Jansson, M.; Nielsen, M.Ø.
2012-01-01
We suggest improved tests for cointegration rank in the vector autoregressive (VAR) model and develop asymptotic distribution theory and local power results. The tests are (quasi-)likelihood ratio tests based on a Gaussian likelihood, but of course the asymptotic results apply more generally. The po
Improved likelihood ratio tests for cointegration rank in the VAR model
Boswijk, H.P.; Jansson, M.; Nielsen, M.Ø.
2015-01-01
We suggest improved tests for cointegration rank in the vector autoregressive (VAR) model and develop asymptotic distribution theory and local power results. The tests are (quasi-)likelihood ratio tests based on a Gaussian likelihood, but as usual the asymptotic results do not require normally distr
Performance on Cloze Tests with Fixed-Ratio and Rational Deletions.
Bachman, Lyle F.
1985-01-01
Describes a study that developed criteria for rationally selecting the words to delete in developing a cloze test. The study also tried to determine the extent to which performance on a cloze test with rational deletions differs from that on a cloze test developed by the fixed-ratio deletion procedure. (SED)
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...
A test on the statistics of derived intensities
de With, G.; Feil, D.
1976-01-01
Variances of X-ray reflexions calculated with the procedure as proposed by McCandlish, Stout & Andrews [Acta Cryst. (1975), A31, 245-249] have been tested against variances determined in an independent way. A satisfying agreement is obtained
The Statistical Assessment of Latent Trait Dimensionality in Psychological Testing
1984-06-01
an upcoming memorial volumn in memory of David Wechsler, (1984). Lamperti, J., Probability, W. A. Benjamin , New York, (1966). Lawley, D.N...Dr. R. Darreli Bock Departissrit ot Education University of Chicago Chicago, IL 60637 » * 1 Dr. Robert Erennan • American CoiisgE Testing
Monte Carlo testing in spatial statistics, with applications to spatial residuals
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...... a two-dimensional smoothed residual field. Second, a goodness-of-fit test of a geostatistical model is performed based on two-dimensional raw residuals....
Testing the DGP model with gravitational lensing statistics
Zhu, Zong-Hong; Sereno, M.
2008-09-01
Aims: The self-accelerating braneworld model (DGP) appears to provide a simple alternative to the standard ΛCDM cosmology to explain the current cosmic acceleration, which is strongly indicated by measurements of type Ia supernovae, as well as other concordant observations. Methods: We investigate observational constraints on this scenario provided by gravitational-lensing statistics using the Cosmic Lens All-Sky Survey (CLASS) lensing sample. Results: We show that a substantial part of the parameter space of the DGP model agrees well with that of radio source gravitational lensing sample. Conclusions: In the flat case, Ω_K=0, the likelihood is maximized, L=L_max, for ΩM = 0.30-0.11+0.19. If we relax the prior on Ω_K, the likelihood peaks at Ω_M,Ωr_c ≃ 0.29, 0.12, slightly in the region of open models. The confidence contours are, however, elongated such that we are unable to discard any of the close, flat or open models.
EDF Statistics for Testing for the Gamma Distribution, with Applications.
1982-08-13
coordinates and then dividing by the spectral density function , which is assumed known up to some unknown scale factor. This gives rise to scaled...periodogram values, xl , ... ,x, which have an approximate G(Ox,m) distribution function, when the correct spectral density function is used. The unknown...scale parameter 0 can be estimated using the technique of section 2.2 and the z I’s found. A test of the !i correctly specified spectral density function can
Paek, Insu
2009-01-01
Three statistical testing procedures well-known in the maximum likelihood approach are the Wald, likelihood ratio (LR), and score tests. Although well-known, the application of these three testing procedures in the logistic regression method to investigate differential item function (DIF) has not been rigorously made yet. Employing a variety of…
Lee, Eul Kyu [Inje Paik University Hospital Jeo-dong, Seoul (Korea, Republic of); Choi, Kwan Woo [Asan Medical Center, Seoul (Korea, Republic of); Jeong, Hoi Woun [The Baekseok Culture University, Cheonan (Korea, Republic of); Jang, Seo Goo [The Soonchunhyang University, Asan (Korea, Republic of); Kim, Ki Won [Kyung Hee University Hospital at Gang-dong, Seoul (Korea, Republic of); Son, Soon Yong [The Wonkwang Health Science University, Iksan (Korea, Republic of); Min, Jung Whan; Son, Jin Hyun [The Shingu University, Sungnam (Korea, Republic of)
2016-09-15
The purpose of this study was to needed basis of measure MRI CAD development for signal to noise ratio (SNR) by pulse sequence analysis from region of interest (ROI) in brain magnetic resonance imaging (MRI) contrast. We examined images of brain MRI contrast enhancement of 117 patients, from January 2005 to December 2015 in a University-affiliated hospital, Seoul, Korea. Diagnosed as one of two brain diseases such as meningioma and cysts SNR for each patient's image of brain MRI were calculated by using Image J. Differences of SNR among two brain diseases were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p < 0.05). We have analysis socio-demographical variables, SNR according to sequence disease, 95% confidence according to SNR of sequence and difference in a mean of SNR. Meningioma results, with the quality of distributions in the order of T1CE, T2 and T1, FLAIR. Cysts results, with the quality of distributions in the order of T2 and T1, T1CE and FLAIR. SNR of MRI sequences of the brain would be useful to classify disease. Therefore, this study will contribute to evaluate brain diseases, and be a fundamental to enhancing the accuracy of CAD development.
Improved Likelihood Ratio Tests for Cointegration Rank in the VAR Model
Boswijk, H. Peter; Jansson, Michael; Nielsen, Morten Ørregaard
. The power gains relative to existing tests are due to two factors. First, instead of basing our tests on the conditional (with respect to the initial observations) likelihood, we follow the recent unit root literature and base our tests on the full likelihood as in, e.g., Elliott, Rothenberg, and Stock......We suggest improved tests for cointegration rank in the vector autoregressive (VAR) model and develop asymptotic distribution theory and local power results. The tests are (quasi-)likelihood ratio tests based on a Gaussian likelihood, but of course the asymptotic results apply more generally...
GROUNDWATER MONITORING: Statistical Methods for Testing Special Background Conditions
Chou, Charissa J.
2004-04-28
This chapter illustrates application of a powerful intra-well testing method referred as the combined Shewhart-CUSUM control chart approach, which can detect abrupt and gradual changes in groundwater parameter concentrations. This method is broadly applicable to groundwater monitoring situations where there is no clearly defined upgradient well or wells, where spatial variability exists in parameter concentrations, or when groundwater flow rate is extremely slow. Procedures for determining the minimum time needed to acquire independent groundwater samples and useful transformations for obtaining normally distributed data are also provided. The control chart method will be insensitive to detect real changes if a preexisting trend is observed in the background data set. A method and a case study describing how a trend observed in a background data set can be removed using a transformation suggested by Gibbons (1994) are presented to illustrate treatment of a preexisting trend.
Testing the dark energy with gravitational lensing statistics
Cao, Shuo; Zhu, Zong-Hong
2012-01-01
We study the redshift distribution of two samples of early-type gravitational lenses, extracted from a larger collection of 122 systems, to constrain the cosmological constant in the LCDM model and the parameters of a set of alternative dark energy models (XCDM, Dvali-Gabadadze-Porrati and Ricci dark energy models), under a spatially flat universe. The likelihood is maximized for $\\Omega_\\Lambda= 0.70 \\pm 0.09$ when considering the sample excluding the SLACS systems (known to be biased towards large image-separation lenses) and no-evolution, and $\\Omega_\\Lambda= 0.81\\pm 0.05$ when limiting to gravitational lenses with image separation larger than 2" and no-evolution. In both cases, results accounting for galaxy evolution are consistent within 1$\\sigma$. The present test supports the accelerated expansion, by excluding the null-hypothesis (i.e., $\\Omega_\\Lambda = 0 $) at more than 4$\\sigma$, regardless of the chosen sample and assumptions on the galaxy evolution. A comparison between competitive world models i...
"What If" Analyses: Ways to Interpret Statistical Significance Test Results Using EXCEL or "R"
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…
EVALUATION OF A NEW MEAN SCALED AND MOMENT ADJUSTED TEST STATISTIC FOR SEM.
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.
Nonparametric statistical tests for the continuous data: the basic concept and the practical use.
Nahm, Francis Sahngun
2016-02-01
Conventional statistical tests are usually called parametric tests. Parametric tests are used more frequently than nonparametric tests in many medical articles, because most of the medical researchers are familiar with and the statistical software packages strongly support parametric tests. Parametric tests require important assumption; assumption of normality which means that distribution of sample means is normally distributed. However, parametric test can be misleading when this assumption is not satisfied. In this circumstance, nonparametric tests are the alternative methods available, because they do not required the normality assumption. Nonparametric tests are the statistical methods based on signs and ranks. In this article, we will discuss about the basic concepts and practical use of nonparametric tests for the guide to the proper use.
Siqueira, Arminda Lucia; Whitehead, Anne; Todd, Susan
2008-02-10
This paper considers methods for testing for superiority or non-inferiority in active-control trials with binary data, when the relative treatment effect is expressed as an odds ratio. Three asymptotic tests for the log-odds ratio based on the unconditional binary likelihood are presented, namely the likelihood ratio, Wald and score tests. All three tests can be implemented straightforwardly in standard statistical software packages, as can the corresponding confidence intervals. Simulations indicate that the three alternatives are similar in terms of the Type I error, with values close to the nominal level. However, when the non-inferiority margin becomes large, the score test slightly exceeds the nominal level. In general, the highest power is obtained from the score test, although all three tests are similar and the observed differences in power are not of practical importance.
Improved ASTM G72 Test Method for Ensuring Adequate Fuel-to-Oxidizer Ratios
Juarez, Alfredo; Harper, Susana Tapia
2016-01-01
The ASTM G72/G72M-15 Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment is currently used to evaluate materials for the ignition susceptibility driven by exposure to external heat in an enriched oxygen environment. Testing performed on highly volatile liquids such as cleaning solvents has proven problematic due to inconsistent test results (non-ignitions). Non-ignition results can be misinterpreted as favorable oxygen compatibility, although they are more likely associated with inadequate fuel-to-oxidizer ratios. Forced evaporation during purging and inadequate sample size were identified as two potential causes for inadequate available sample material during testing. In an effort to maintain adequate fuel-to-oxidizer ratios within the reaction vessel during test, several parameters were considered, including sample size, pretest sample chilling, pretest purging, and test pressure. Tests on a variety of solvents exhibiting a range of volatilities are presented in this paper. A proposed improvement to the standard test protocol as a result of this evaluation is also presented. Execution of the final proposed improved test protocol outlines an incremental step method of determining optimal conditions using increased sample sizes while considering test system safety limits. The proposed improved test method increases confidence in results obtained by utilizing the ASTM G72 autogenous ignition temperature test method and can aid in the oxygen compatibility assessment of highly volatile liquids and other conditions that may lead to false non-ignition results.
A Visual Basic program for analyzing oedometer test results and evaluating intergranular void ratio
Monkul, M. Murat; Önal, Okan
2006-06-01
A visual basic program (POCI) is proposed and explained in order to analyze oedometer test results. Oedometer test results have vital importance from geotechnical point of view, since settlement requirements usually control the design of foundations. The software POCI is developed in order perform the necessary calculations for convential oedometer test. The change of global void ratio and stress-strain characteristics can be observed both numerically and graphically. It enables the users to calculate some parameters such as coefficient of consolidation, compression index, recompression index, and preconsolidation pressure depending on the type and stress history of the soil. Moreover, it adopts the concept of intergranular void ratio which may be important especially in the compression behavior of sandy soils. POCI shows the variation of intergranular void ratio and also enables the users to calculate granular compression index.
Wald Sequential Probability Ratio Test for Analysis of Orbital Conjunction Data
Carpenter, J. Russell; Markley, F. Landis; Gold, Dara
2013-01-01
We propose a Wald Sequential Probability Ratio Test for analysis of commonly available predictions associated with spacecraft conjunctions. Such predictions generally consist of a relative state and relative state error covariance at the time of closest approach, under the assumption that prediction errors are Gaussian. We show that under these circumstances, the likelihood ratio of the Wald test reduces to an especially simple form, involving the current best estimate of collision probability, and a similar estimate of collision probability that is based on prior assumptions about the likelihood of collision.
The Effects of Repeated Cooperative Testing in an Introductory Statistics Course.
Giraud, Gerald; Enders, Craig
Cooperative testing seems a logical complement to cooperative learning, but it is counter to traditional testing procedures and is viewed by some as an opportunity for cheating and freeloading on the efforts of other test takers. This study examined the practice of cooperative testing in introductory statistics. Findings indicate that students had…
Xu, Maoqi; Chen, Liang
2016-10-21
The individual sample heterogeneity is one of the biggest obstacles in biomarker identification for complex diseases such as cancers. Current statistical models to identify differentially expressed genes between disease and control groups often overlook the substantial human sample heterogeneity. Meanwhile, traditional nonparametric tests lose detailed data information and sacrifice the analysis power, although they are distribution free and robust to heterogeneity. Here, we propose an empirical likelihood ratio test with a mean-variance relationship constraint (ELTSeq) for the differential expression analysis of RNA sequencing (RNA-seq). As a distribution-free nonparametric model, ELTSeq handles individual heterogeneity by estimating an empirical probability for each observation without making any assumption about read-count distribution. It also incorporates a constraint for the read-count overdispersion, which is widely observed in RNA-seq data. ELTSeq demonstrates a significant improvement over existing methods such as edgeR, DESeq, t-tests, Wilcoxon tests and the classic empirical likelihood-ratio test when handling heterogeneous groups. It will significantly advance the transcriptomics studies of cancers and other complex disease.
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.
Cikota, Aleksandar; Marleau, Francine
2016-01-01
We investigate limits on the extinction values of Type Ia supernovae to statistically determine the most probable color excess, E(B-V), with galactocentric distance, and use these statistics to determine the absorption-to-reddening ratio, $R_V$, for dust in the host galaxies. We determined pixel-based dust mass surface density maps for 59 galaxies from the Key Insight on Nearby Galaxies: a Far-Infrared Survey with \\textit{Herschel} (KINGFISH, Kennicutt et al. (2011)). We use Type Ia supernova spectral templates (Hsiao et al. 2007) to develop a Monte Carlo simulation of color excess E(B-V) with $R_V$ = 3.1 and investigate the color excess probabilities E(B-V) with projected radial galaxy center distance. Additionally, we tested our model using observed spectra of SN 1989B, SN 2002bo and SN 2006X, which occurred in three KINGFISH galaxies. Finally, we determined the most probable reddening for Sa-Sap, Sab-Sbp, Sbc-Scp, Scd-Sdm, S0 and Irregular galaxy classes as a function of $R/R_{25}$. We find that the larges...
An Efficient Implementation of Fixed Failure-Rate Ratio Test for GNSS Ambiguity Resolution
Hou, Yanqing; Verhagen, Sandra; Wu, Jie
2016-01-01
Ambiguity Resolution (AR) plays a vital role in precise GNSS positioning. Correctly-fixed integer ambiguities can significantly improve the positioning solution, while incorrectly-fixed integer ambiguities can bring large positioning errors and, therefore, should be avoided. The ratio test is an extensively used test to validate the fixed integer ambiguities. To choose proper critical values of the ratio test, the Fixed Failure-rate Ratio Test (FFRT) has been proposed, which generates critical values according to user-defined tolerable failure rates. This contribution provides easy-to-implement fitting functions to calculate the critical values. With a massive Monte Carlo simulation, the functions for many different tolerable failure rates are provided, which enriches the choices of critical values for users. Moreover, the fitting functions for the fix rate are also provided, which for the first time allows users to evaluate the conditional success rate, i.e., the success rate once the integer candidates are accepted by FFRT. The superiority of FFRT over the traditional ratio test regarding controlling the failure rate and preventing unnecessary false alarms is shown by a simulation and a real data experiment. In the real data experiment with a baseline of 182.7 km, FFRT achieved much higher fix rates (up to 30% higher) and the same level of positioning accuracy from fixed solutions as compared to the traditional critical value. PMID:27347949
An Efficient Implementation of Fixed Failure-Rate Ratio Test for GNSS Ambiguity Resolution
Yanqing Hou
2016-06-01
Full Text Available Ambiguity Resolution (AR plays a vital role in precise GNSS positioning. Correctly-fixed integer ambiguities can significantly improve the positioning solution, while incorrectly-fixed integer ambiguities can bring large positioning errors and, therefore, should be avoided. The ratio test is an extensively used test to validate the fixed integer ambiguities. To choose proper critical values of the ratio test, the Fixed Failure-rate Ratio Test (FFRT has been proposed, which generates critical values according to user-defined tolerable failure rates. This contribution provides easy-to-implement fitting functions to calculate the critical values. With a massive Monte Carlo simulation, the functions for many different tolerable failure rates are provided, which enriches the choices of critical values for users. Moreover, the fitting functions for the fix rate are also provided, which for the first time allows users to evaluate the conditional success rate, i.e., the success rate once the integer candidates are accepted by FFRT. The superiority of FFRT over the traditional ratio test regarding controlling the failure rate and preventing unnecessary false alarms is shown by a simulation and a real data experiment. In the real data experiment with a baseline of 182.7 km, FFRT achieved much higher fix rates (up to 30% higher and the same level of positioning accuracy from fixed solutions as compared to the traditional critical value.
An Efficient Implementation of Fixed Failure-Rate Ratio Test for GNSS Ambiguity Resolution.
Hou, Yanqing; Verhagen, Sandra; Wu, Jie
2016-06-23
Ambiguity Resolution (AR) plays a vital role in precise GNSS positioning. Correctly-fixed integer ambiguities can significantly improve the positioning solution, while incorrectly-fixed integer ambiguities can bring large positioning errors and, therefore, should be avoided. The ratio test is an extensively used test to validate the fixed integer ambiguities. To choose proper critical values of the ratio test, the Fixed Failure-rate Ratio Test (FFRT) has been proposed, which generates critical values according to user-defined tolerable failure rates. This contribution provides easy-to-implement fitting functions to calculate the critical values. With a massive Monte Carlo simulation, the functions for many different tolerable failure rates are provided, which enriches the choices of critical values for users. Moreover, the fitting functions for the fix rate are also provided, which for the first time allows users to evaluate the conditional success rate, i.e., the success rate once the integer candidates are accepted by FFRT. The superiority of FFRT over the traditional ratio test regarding controlling the failure rate and preventing unnecessary false alarms is shown by a simulation and a real data experiment. In the real data experiment with a baseline of 182.7 km, FFRT achieved much higher fix rates (up to 30% higher) and the same level of positioning accuracy from fixed solutions as compared to the traditional critical value.
A note on imperfect hedging: a method for testing stability of the hedge ratio
Michal Černý
2012-01-01
Full Text Available Companies producing, processing and consuming commodities in the production process often hedge their commodity expositions using derivative strategies based on different, highly correlated underlying commodities. Once the open position in a commodity is hedged using a derivative position with another underlying commodity, the appropriate hedge ratio must be determined in order the hedge relationship be as effective as possible. However, it is questionable whether the hedge ratio determined at the inception of the risk management strategy remains stable over the whole period for which the hedging strategy exists. Usually it is assumed that in the short run, the relationship (say, correlation between the two commodities remains stable, while in the long run it may vary. We propose a method, based on statistical theory of stability, for on-line detection whether market movements of prices of the commodities involved in the hedge relationship indicate that the hedge ratio may have been subject to a recent change. The change in the hedge ratio decreases the effectiveness of the original hedge relationship and creates a new open position. The method proposed should inform the risk manager that it could be reasonable to adjust the derivative strategy in a way reflecting the market conditions after the change in the hedge ratio.
Steffen, Jason H.; Ford, Eric B.; Rowe, Jason F.; Fabrycky, Daniel C.; Holman, Matthew J.; Welsh, William F.; Borucki, William J.; Batalha, Natalie M.; Bryson, Steve; Caldwell, Douglas A.; Ciardi, David R.; Jenkins, Jon M.; Kjeldsen, Hans; Koch, David G.; Prsa, 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 (Q6) 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 sy...
Cikota, Aleksandar [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. München (Germany); Deustua, Susana [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Marleau, Francine, E-mail: acikota@eso.org [Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstrasse 25/8, A-6020 Innsbruck (Austria)
2016-03-10
We investigate limits on the extinction values of Type Ia supernovae (SNe Ia) to statistically determine the most probable color excess, E(B – V), with galactocentric distance, and use these statistics to determine the absorption-to-reddening ratio, R{sub V}, for dust in the host galaxies. We determined pixel-based dust mass surface density maps for 59 galaxies from the Key Insight on Nearby Galaxies: a Far-infrared Survey with Herschel (KINGFISH). We use SN Ia spectral templates to develop a Monte Carlo simulation of color excess E(B – V) with R{sub V} = 3.1 and investigate the color excess probabilities E(B – V) with projected radial galaxy center distance. Additionally, we tested our model using observed spectra of SN 1989B, SN 2002bo, and SN 2006X, which occurred in three KINGFISH galaxies. Finally, we determined the most probable reddening for Sa–Sap, Sab–Sbp, Sbc–Scp, Scd–Sdm, S0, and irregular galaxy classes as a function of R/R{sub 25}. We find that the largest expected reddening probabilities are in Sab–Sb and Sbc–Sc galaxies, while S0 and irregular galaxies are very dust poor. We present a new approach for determining the absorption-to-reddening ratio R{sub V} using color excess probability functions and find values of R{sub V} = 2.71 ± 1.58 for 21 SNe Ia observed in Sab–Sbp galaxies, and R{sub V} = 1.70 ± 0.38, for 34 SNe Ia observed in Sbc–Scp galaxies.
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.
Evidence Based Medicine; Positive and Negative Likelihood Ratios of Diagnostic Tests
Alireza Baratloo
2015-10-01
Full Text Available In the previous two parts of educational manuscript series in Emergency, we explained some screening characteristics of diagnostic tests including accuracy, sensitivity, specificity, and positive and negative predictive values. In the 3rd part we aimed to explain positive and negative likelihood ratio (LR as one of the most reliable performance measures of a diagnostic test. To better understand this characteristic of a test, it is first necessary to fully understand the concept of sensitivity and specificity. So we strongly advise you to review the 1st part of this series again. In short, the likelihood ratios are about the percentage of people with and without a disease but having the same test result. The prevalence of a disease can directly influence screening characteristics of a diagnostic test, especially its sensitivity and specificity. Trying to eliminate this effect, LR was developed. Pre-test probability of a disease multiplied by positive or negative LR can estimate post-test probability. Therefore, LR is the most important characteristic of a test to rule out or rule in a diagnosis. A positive likelihood ratio > 1 means higher probability of the disease to be present in a patient with a positive test. The further from 1, either higher or lower, the stronger the evidence to rule in or rule out the disease, respectively. It is obvious that tests with LR close to one are less practical. On the other hand, LR further from one will have more value for application in medicine. Usually tests with 0.1 < LR > 10 are considered suitable for implication in routine practice.
Two-IMU FDI performance of the sequential probability ratio test during shuttle entry
Rich, T. M.
1976-01-01
Performance data for the sequential probability ratio test (SPRT) during shuttle entry are presented. Current modeling constants and failure thresholds are included for the full mission 3B from entry through landing trajectory. Minimum 100 percent detection/isolation failure levels and a discussion of the effects of failure direction are presented. Finally, a limited comparison of failures introduced at trajectory initiation shows that the SPRT algorithm performs slightly worse than the data tracking test.
Comparison of IRT Likelihood Ratio Test and Logistic Regression DIF Detection Procedures
Atar, Burcu; Kamata, Akihito
2011-01-01
The Type I error rates and the power of IRT likelihood ratio test and cumulative logit ordinal logistic regression procedures in detecting differential item functioning (DIF) for polytomously scored items were investigated in this Monte Carlo simulation study. For this purpose, 54 simulation conditions (combinations of 3 sample sizes, 2 sample…
Comparison of IRT Likelihood Ratio Test and Logistic Regression DIF Detection Procedures
Atar, Burcu; Kamata, Akihito
2011-01-01
The Type I error rates and the power of IRT likelihood ratio test and cumulative logit ordinal logistic regression procedures in detecting differential item functioning (DIF) for polytomously scored items were investigated in this Monte Carlo simulation study. For this purpose, 54 simulation conditions (combinations of 3 sample sizes, 2 sample…
Testing for phylogenetic signal in biological traits: the ubiquity of cross-product statistics.
Pavoine, Sandrine; Ricotta, Carlo
2013-03-01
To evaluate rates of evolution, to establish tests of correlation between two traits, or to investigate to what degree the phylogeny of a species assemblage is predictive of a trait value so-called tests for phylogenetic signal are used. Being based on different approaches, these tests are generally thought to possess quite different statistical performances. In this article, we show that the Blomberg et al. K and K*, the Abouheif index, the Moran's I, and the Mantel correlation are all based on a cross-product statistic, and are thus all related to each other when they are associated to a permutation test of phylogenetic signal. What changes is only the way phylogenetic and trait similarities (or dissimilarities) among the tips of a phylogeny are computed. The definitions of the phylogenetic and trait-based (dis)similarities among tips thus determines the performance of the tests. We shortly discuss the biological and statistical consequences (in terms of power and type I error of the tests) of the observed relatedness among the statistics that allow tests for phylogenetic signal. Blomberg et al. K* statistic appears as one on the most efficient approaches to test for phylogenetic signal. When branch lengths are not available or not accurate, Abouheif's Cmean statistic is a powerful alternative to K*.
A semiparametric Wald statistic for testing logistic regression models based on case-control data
WAN ShuWen
2008-01-01
We propose a semiparametric Wald statistic to test the validity of logistic regression models based on case-control data.The test statistic is constructed using a semiparametric ROC curve estimator and a nonparametric ROC curve estimator.The statistic has an asymptotic chi-squared distribution and is an alternative to the Kolmogorov-Smirnov-type statistic proposed by Qin and Zhang in 1997,the chi-squared-type statistic proposed by Zhang in 1999 and the information matrix test statistic proposed by Zhang in 2001.The statistic is easy to compute in the sense that it requires none of the following methods:using a bootstrap method to find its critical values,partitioning the sample data or inverting a high-dimensional matrix.We present some results on simulation and on analysis of two real examples.Moreover,we discuss how to extend our statistic to a family of statistics and how to construct its Kolmogorov-Smirnov counterpart.
Carbon isotope ratio mass spectrometry for detection of endogenous steroid use: a testing strategy.
Ahrens, Brian D; Butch, Anthony W
2013-07-01
Isotope ratio mass spectrometry (IRMS) testing is performed to determine if an atypical steroid profile is due to administration of an endogenous steroid. Androsterone (Andro) and etiocholanolone (Etio), and/or the androstanediols (5α- and 5β-androstane-3α,17β-diol) are typically analyzed by IRMS to determine the (13) C/(12) C ratio. The ratios of these target compounds are compared to the (13) C/(12) C ratio of an endogenous reference compound (ERC) such as 5β-pregnane-3α,20α-diol (Pdiol). Concentrations of Andro and Etio are high so (13) C/(12) C ratios can easily be measured in most urine samples. Despite the potentially improved sensitivity of the androstanediols for detecting the use of some testosterone formulations, additional processing steps are often required that increase labour costs and turnaround times. Since this can be problematic when performing large numbers of IRMS measurements, we established thresholds for Andro and Etio that can be used to determine the need for additional androstanediol testing. Using these criteria, 105 out of 2639 urine samples exceeded the Andro and/or Etio thresholds, with 52 of these samples being positive based on Andro and Etio IRMS testing alone. The remaining 53 urine samples had androstanediol IRMS testing performed and 3 samples were positive based on the androstanediol results. A similar strategy was used to establish a threshold for Pdiol to identify athletes with relatively (13) C-depleted values so that an alternative ERC can be used to confirm or establish a true endogenous reference value. Adoption of a similar strategy by other laboratories can significantly reduce IRMS sample processing and analysis times, thereby increasing testing capacity.
Schneider, Peter
2016-01-01
We derive a new relation between cosological distances, valid in any (statistically) isotropic space-time and independent of cosmological parameters or even the validity of the field equation of General Relativity. In particular, this relation yields an equation between those distance ratios which are the geometrical factors determining the strength of the gravitational lensing effect of mass concentrations. Considering a combination of weak lensing shear ratios, based on lenses at two different redshifts, and sources at three different redshifts, we derive a relation between shear-ratio tests which must be identically satisfied. A redshift-dependent multiplicative bias in shear estimates will violate this relation, and thus can be probed by this generalized shear-ratio test. Combining the lensing effect for lenses at three different redshifts and three different source redshifts, a relation between shear ratios is derived which must be valid independent of a multiplicative bias. We propose these generalized ...
Mnemonic Aids during Tests: Worthless Frivolity or Effective Tool in Statistics Education?
Larwin, Karen H.; Larwin, David A.; Gorman, Jennifer
2012-01-01
Researchers have explored many pedagogical approaches in an effort to assist students in finding understanding and comfort in required statistics courses. This study investigates the impact of mnemonic aids used during tests on students' statistics course performance in particular. In addition, the present study explores several hypotheses that…
LeMire, Steven D.
2010-01-01
This paper proposes an argument framework for the teaching of null hypothesis statistical testing and its application in support of research. Elements of the Toulmin (1958) model of argument are used to illustrate the use of p values and Type I and Type II error rates in support of claims about statistical parameters and subject matter research…
The effects of multiple features of alternatively spliced exons on the KA/KS ratio test
Chen Feng-Chi
2006-05-01
Full Text Available Abstract Background The evolution of alternatively spliced exons (ASEs is of primary interest because these exons are suggested to be a major source of functional diversity of proteins. Many exon features have been suggested to affect the evolution of ASEs. However, previous studies have relied on the KA/KS ratio test without taking into consideration information sufficiency (i.e., exon length > 75 bp, cross-species divergence > 5% of the studied exons, leading to potentially biased interpretations. Furthermore, which exon feature dominates the results of the KA/KS ratio test and whether multiple exon features have additive effects have remained unexplored. Results In this study, we collect two different datasets for analysis – the ASE dataset (which includes lineage-specific ASEs and conserved ASEs and the ACE dataset (which includes only conserved ASEs. We first show that information sufficiency can significantly affect the interpretation of relationship between exons features and the KA/KS ratio test results. After discarding exons with insufficient information, we use a Boolean method to analyze the relationship between test results and four exon features (namely length, protein domain overlapping, inclusion level, and exonic splicing enhancer (ESE frequency for the ASE dataset. We demonstrate that length and protein domain overlapping are dominant factors, and they have similar impacts on test results of ASEs. In addition, despite the weak impacts of inclusion level and ESE motif frequency when considered individually, combination of these two factors still have minor additive effects on test results. However, the ACE dataset shows a slightly different result in that inclusion level has a marginally significant effect on test results. Lineage-specific ASEs may have contributed to the difference. Overall, in both ASEs and ACEs, protein domain overlapping is the most dominant exon feature while ESE frequency is the weakest one in affecting
Selecting the most appropriate inferential statistical test for your quantitative research study.
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.
Yingjun Jiang
2015-04-01
Full Text Available In order to better understand the mechanical properties of graded crushed rocks (GCRs and to optimize the relevant design, a numerical test method based on the particle flow modeling technique PFC2D is developed for the California bearing ratio (CBR test on GCRs. The effects of different testing conditions and micro-mechanical parameters used in the model on the CBR numerical results have been systematically studied. The reliability of the numerical technique is verified. The numerical results suggest that the influences of the loading rate and Poisson's ratio on the CBR numerical test results are not significant. As such, a loading rate of 1.0–3.0 mm/min, a piston diameter of 5 cm, a specimen height of 15 cm and a specimen diameter of 15 cm are adopted for the CBR numerical test. The numerical results reveal that the CBR values increase with the friction coefficient at the contact and shear modulus of the rocks, while the influence of Poisson's ratio on the CBR values is insignificant. The close agreement between the CBR numerical results and experimental results suggests that the numerical simulation of the CBR values is promising to help assess the mechanical properties of GCRs and to optimize the grading design. Besides, the numerical study can provide useful insights on the mesoscopic mechanism.
Petersen, Helga Nørgaard; Thomason, James L.; Minty, Ross;
2015-01-01
The interfacial properties as Interfacial Shear Stress (IFSS) in fibre reinforced polymers are essential for further understanding of the mechanical properties of the composite. In this work a single fibre testing method is used in combination with an epoxy matrix made from Araldite 506 epoxy resin...... and triethylenetetramine (TETA) hardener. The IFSS was measured by a microbond test developed for a Thermal Mechanical Analyzer. The preliminary results indicate that IFSS has an inverse dependency of both testing temperature and the mixing ratio of hardener and epoxy resin. Especially interesting was the decreasing...
A Third Moment Adjusted Test Statistic for Small Sample Factor Analysis.
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.
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.
Honarmand, Azim; Safavi, Mohammadreza; Yaraghi, Ahmad; Attari, Mohammadali; Khazaei, Mehdi; Zamani, Majid
2015-01-01
Preoperative airway assessment tests have been presented to help in anticipating a difficult airway. We conducted this study to compare five methods in prediction of difficult laryngoscopy: Neck circumference (NC), NC to thyromental distance ratio (NC/TMD), the ratio of height to thyromental distance (RHTMD), upper lip bite test (ULBT) and Mallampati test (MMT). These five methods are the most commonly used ones and have different powers for it. It was not clear which of these methods predicts difficult laryngoscopy better. Six hundred consecutive patients participated in this study. NC, NC/TMD and RHTMD were measured, and ULBT and MMT were performed and recorded. The laryngoscopy view was graded according to Cormack and Lehane's scale (CLS) and difficult laryngoscopy was defined as CLS grades 3 and 4. Accuracy of tests in predicting difficult laryngoscopy was assessed using the area under a receiver-operating characteristic curve. The area under the curve in ULBT and RHTMD were significantly larger than that in TMD, NC and MMT. No statistically significant differences were noted between TMD, NC and MMT (all P > 0.05) (ULBT = RHTMD > NC/TMD > TMD = NC = MMT). RHTMD (>22.7 cm) exhibited the highest sensitivity (sensitivity = 64.77, 95% confidence interval [CI]: 53.9-74.7) and the most specific test was ULBT (specificity = 99.41%, 95% CI: 98.3-99.9). RHTMD and ULBT as simple preoperative bedside tests have a higher level of accuracy compared to NC/TMD, TMD, NC, MMT in predicting a difficult airway.
Statistical Tests for the Reciprocal of a Normal Mean with a Known Coefficient of Variation
Wararit Panichkitkosolkul
2015-01-01
Full Text Available An asymptotic test and an approximate test for the reciprocal of a normal mean with a known coefficient of variation were proposed in this paper. The asymptotic test was based on the expectation and variance of the estimator of the reciprocal of a normal mean. The approximate test used the approximate expectation and variance of the estimator by Taylor series expansion. A Monte Carlo simulation study was conducted to compare the performance of the two statistical tests. Simulation results showed that the two proposed tests performed well in terms of empirical type I errors and power. Nevertheless, the approximate test was easier to compute than the asymptotic test.
Spent fuel sabotage aerosol ratio program : FY 2004 test and data summary.
Brucher, Wenzel (Gesellschaft fur Anlagen- und Reaktorsicherheit, Germany); Koch, Wolfgang (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Pretzsch, Gunter Guido (Gesellschaft fur Anlagen- und Reaktorsicherheit, Germany); Loiseau, Olivier (Institut de Radioprotection et de Surete Nucleaire, France); Mo, Tin (U.S. Nuclear Regulatory Commission, Washington, DC); Billone, Michael C. (Argonne National Laboratory, Argonne, IL); Autrusson, Bruno A. (Institut de Radioprotection et de Surete Nucleaire, France); Young, F. I. (U.S. Nuclear Regulatory Commission, Washington, DC); Coats, Richard Lee; Burtseva, Tatiana (Argonne National Laboratory, Argonne, IL); Luna, Robert Earl; Dickey, Roy R.; Sorenson, Ken Bryce; Nolte, Oliver (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Thompson, Nancy Slater (U.S. Department of Energy, Washington, DC); Hibbs, Russell S. (U.S. Department of Energy, Washington, DC); Gregson, Michael Warren; Lange, Florentin (Gesellschaft fur Anlagen- und Reaktorsicherheit, Germany); Molecke, Martin Alan; Tsai, Han-Chung (Argonne National Laboratory, Argonne, IL)
2005-07-01
This multinational, multi-phase spent fuel sabotage test program is quantifying the aerosol particles produced when the products of a high energy density device (HEDD) interact with and explosively particulate test rodlets that contain pellets of either surrogate materials or actual spent fuel. This program has been underway for several years. This program provides data that are relevant to some sabotage scenarios in relation to spent fuel transport and storage casks, and associated risk assessments. The program also provides significant technical and political benefits in international cooperation. We are quantifying the Spent Fuel Ratio (SFR), the ratio of the aerosol particles released from HEDD-impacted actual spent fuel to the aerosol particles produced from surrogate materials, measured under closely matched test conditions, in a contained test chamber. In addition, we are measuring the amounts, nuclide content, size distribution of the released aerosol materials, and enhanced sorption of volatile fission product nuclides onto specific aerosol particle size fractions. These data are the input for follow-on modeling studies to quantify respirable hazards, associated radiological risk assessments, vulnerability assessments, and potential cask physical protection design modifications. This document includes an updated description of the test program and test components for all work and plans made, or revised, during FY 2004. It also serves as a program status report as of the end of FY 2004. All available test results, observations, and aerosol analyses plus interpretations--primarily for surrogate material Phase 2 tests, series 2/5A through 2/9B, using cerium oxide sintered ceramic pellets are included. Advanced plans and progress are described for upcoming tests with unirradiated, depleted uranium oxide and actual spent fuel test rodlets. This spent fuel sabotage--aerosol test program is coordinated with the international Working Group for Sabotage Concerns of
Diagnostic Role of Captopril Challenge Test in Korean Subjects with High Aldosterone-to-Renin Ratios
Jung Hee Kim
2016-06-01
Full Text Available BackgroundDiagnosis of primary aldosteronism (PA begins with aldosterone-to-renin ratio (ARR measurement followed by confirmative tests. However, the ARR has high false positive rates which led to unnecessary confirmatory tests. Captopril challenge test (CCT has been used as one of confirmatory tests, but the accuracy of it in the diagnosis of PA is still controversial. We aimed to examine the clinical efficacy of CCT as a post-screening test in PA.MethodsIn a prospective study, we enrolled subjects with suspected PA who had hypertension and ARR >20 (ng/dL/(ng/mL/hr. Sixty-four patients who underwent both the saline infusion test and the CCT were included.ResultsThe diagnostic performance of plasma aldosterone concentration (PAC post-CCT was greater than that of ARR post-CCT and ARR pre-CCT in PA (area under the curve=0.956, 0.797, and 0.748, respectively; P=0.001. A cut-off value of 13 ng/dL showed the highest diagnostic odds ratio considering PAC post-CCT at 60 and 90 minutes. A PAC post-CCT of 19 ng/dL had a specificity of 100%, which can be used as a cut-off value for the confirmative test. Determining the diagnostic performance of PAC post-CCT at 90 minutes was sufficient for PA diagnosis. Subjects with PAC post-CCT at 90 minutes <13 ng/dL are less likely to have PA, and those with PAC post-CCT at 90 minutes ≥13 but <19 ng/dL should undergo secondary confirmatory tests.ConclusionThe CCT test may be a reliable post-screening test to avoid the hospitalization in the setting of falsely elevated ARR screening tests.
A statistical test for drainage network recognition using MeanStreamDrop analysis
Corrado Cencetti
2015-07-01
Full Text Available This paper provides a new statistical test to evaluate the threshold of validity for the Mean Stream Drop analysis. In the case of a constant area threshold, the method aims to provide a unique threshold value to extract the drainage network through a statistical test more efficient than those widely used. The proposal starts from the assumption that a minimum threshold value exists suitable for drainage network extraction. Then, the method proceeds with Horton–Strahler ordering of the network and statistically analysing the network geometry. This procedure is repeated for all the threshold values in the set under investigation, using a statistical permutation test, called APTDTM (Adjusted Permutation Test based on the Difference between Trimmed Means. Statistical significance is evaluated by p-values adjusted to account for multiple comparisons. As a final result of the statistical analysis, the right threshold value for the specific basin is identified. Classical procedures are based on a set of two sample t-tests. However, this method relies on the assumptions of normality and homogeneity of variance, which are unlikely to hold in practice. The APTDTM test presented here provides accurate p-values even when the sampling distribution is not close to normal, or there is heteroskedasticity in the data.
Chloride accelerated test: influence of silica fume, water/binder ratio and concrete cover thickness
E. Pereira
Full Text Available In developed countries like the UK, France, Italy and Germany, it is estimated that spending on maintenance and repair is practically the same as investment in new constructions. Therefore, this paper aims to study different ways of interfering in the corrosion kinetic using an accelerated corrosion test - CAIM, that simulates the chloride attack. The three variables are: concrete cover thickness, use of silica fume and the water/binder ratio. It was found, by analysis of variance of the weight loss of the steel bars and chloride content in the concrete cover thickness, there is significant influence of the three variables. Also, the results indicate that the addition of silica fume is the path to improve the corrosion protection of low water/binder ratio concretes (like 0.4 and elevation of the concrete cover thickness is the most effective solution to increase protection of high water/binder ratio concrete (above 0.5.
Yang, Yang; Wise, Carol A; Gordon, Derek; Finch, Stephen J
2008-01-01
The purpose of this work is the development of a family-based association test that allows for random genotyping errors and missing data and makes use of information on affected and unaffected pedigree members. We derive the conditional likelihood functions of the general nuclear family for the following scenarios: complete parental genotype data and no genotyping errors; only one genotyped parent and no genotyping errors; no parental genotype data and no genotyping errors; and no parental genotype data with genotyping errors. We find maximum likelihood estimates of the marker locus parameters, including the penetrances and population genotype frequencies under the null hypothesis that all penetrance values are equal and under the alternative hypothesis. We then compute the likelihood ratio test. We perform simulations to assess the adequacy of the central chi-square distribution approximation when the null hypothesis is true. We also perform simulations to compare the power of the TDT and this likelihood-based method. Finally, we apply our method to 23 SNPs genotyped in nuclear families from a recently published study of idiopathic scoliosis (IS). Our simulations suggest that this likelihood ratio test statistic follows a central chi-square distribution with 1 degree of freedom under the null hypothesis, even in the presence of missing data and genotyping errors. The power comparison shows that this likelihood ratio test is more powerful than the original TDT for the simulations considered. For the IS data, the marker rs7843033 shows the most significant evidence for our method (p = 0.0003), which is consistent with a previous report, which found rs7843033 to be the 2nd most significant TDTae p value among a set of 23 SNPs.
Average projection type weighted Cramér-von Mises statistics for testing some distributions
CUI; Hengjian(崔恒建)
2002-01-01
This paper addresses the problem of testing goodness-of-fit for several important multivariate distributions: (Ⅰ) Uniform distribution on p-dimensional unit sphere; (Ⅱ) multivariate standard normal distribution; and (Ⅲ) multivariate normal distribution with unknown mean vector and covariance matrix. The average projection type weighted Cramér-yon Mises test statistic as well as estimated and weighted Cramér-von Mises statistics for testing distributions (Ⅰ), (Ⅱ) and (Ⅲ) are constructed via integrating projection direction on the unit sphere, and the asymptotic distributions and the expansions of those test statistics under the null hypothesis are also obtained. Furthermore, the approach of this paper can be applied to testing goodness-of-fit for elliptically contoured distributions.
Krobbuaban, Banjong; Diregpoke, Siriwan; Kumkeaw, Sujarit; Tanomsat, Malin
2005-11-01
Preoperative evaluation of anatomical landmarks and clinical factors help identify potentially difficult laryngoscopies; however, predictive reliability is unclear. Because the ratio of height to thyromental distance (RHTMD) has a demonstrably better predictive value than the thyromental distance (TMD), we evaluated the predictive value and odds ratios of RHTMD versus mouth opening, TMD, neck movement, and oropharyngeal view (modified Mallampati). We collected data on 550 consecutive patients scheduled for elective-surgery general anesthesia requiring endotracheal intubation and then assessed all five factors before surgery. An experienced anesthesiologist, not apprised of the recorded preoperative airway assessment, performed the laryngoscopy and grading (as per Cormack and Lehane's classification). Difficult laryngoscopy (Grade 3 or 4) occurred in 69 patients (12.5%). RHTMD had a higher sensitivity, positive predictive value, and fewer false negatives than the other variables tested. In the multivariate analysis, three criteria were found independent for difficult laryngoscopy (neck movement or =23.5). The odds ratio (95% confidence interval) of the RHTMD, Mallampati class, and neck movement were 6.72 (3.29-13.72), 2.96 (1.63-5.35), and 2.73 (1.14-6.51), respectively. The odds ratio for RHTMD was the largest and thus may prove a useful screening test for difficult laryngoscopy.
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...... 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...
How well do test case prioritization techniques support statistical fault localization
Tse, TH; Jiang, B.; Zhang, Z; Chen, TY
2009-01-01
In continuous integration, a tight integration of test case prioritization techniques and fault-localization techniques may both expose failures faster and locate faults more effectively. Statistical fault-localization techniques use the execution information collected during testing to locate faults. Executing a small fraction of a prioritized test suite reduces the cost of testing, and yet the subsequent fault localization may suffer. This paper presents the first empirical study to examine...
Downward, L.; Booth, C.H.; Lukens, W.W.; Bridges, F.
2006-07-25
A general problem when fitting EXAFS data is determining whether particular parameters are statistically significant. The F-test is an excellent way of determining relevancy in EXAFS because it only relies on the ratio of the fit residual of two possible models, and therefore the data errors approximately cancel. Although this test is widely used in crystallography (there, it is often called a 'Hamilton test') and has been properly applied to EXAFS data in the past, it is very rarely applied in EXAFS analysis. We have implemented a variation of the F-test adapted for EXAFS data analysis in the RSXAP analysis package, and demonstrate its applicability with a few examples, including determining whether a particular scattering shell is warranted, and differentiating between two possible species or two possible structures in a given shell.
Weighted pedigree-based statistics for testing the association of rare variants.
Shugart, Yin Yao; Zhu, Yun; Guo, Wei; Xiong, Momiao
2012-11-24
With the advent of next-generation sequencing (NGS) technologies, researchers are now generating a deluge of data on high dimensional genomic variations, whose analysis is likely to reveal rare variants involved in the complex etiology of disease. Standing in the way of such discoveries, however, is the fact that statistics for rare variants are currently designed for use with population-based data. In this paper, we introduce a pedigree-based statistic specifically designed to test for rare variants in family-based data. The additional power of pedigree-based statistics stems from the fact that while rare variants related to diseases or traits of interest occur only infrequently in populations, in families with multiple affected individuals, such variants are enriched. Note that while the proposed statistic can be applied with and without statistical weighting, our simulations show that its power increases when weighting (WSS and VT) are applied. Our working hypothesis was that, since rare variants are concentrated in families with multiple affected individuals, pedigree-based statistics should detect rare variants more powerfully than population-based statistics. To evaluate how well our new pedigree-based statistics perform in association studies, we develop a general framework for sequence-based association studies capable of handling data from pedigrees of various types and also from unrelated individuals. In short, we developed a procedure for transforming population-based statistics into tests for family-based associations. Furthermore, we modify two existing tests, the weighted sum-square test and the variable-threshold test, and apply both to our family-based collapsing methods. We demonstrate that the new family-based tests are more powerful than corresponding population-based test and they generate a reasonable type I error rate.To demonstrate feasibility, we apply the newly developed tests to a pedigree-based GWAS data set from the Framingham Heart
CUSUM-Based Person-Fit Statistics for Adaptive Testing. Research Report 99-05.
van Krimpen-Stoop, Edith M. L. A.; Meijer, Rob R.
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), the use of person-fit analysis has hardly been…
The Comparability of the Statistical Characteristics of Test Items Generated by Computer Algorithms.
Meisner, Richard; And Others
This paper presents a study on the generation of mathematics test items using algorithmic methods. The history of this approach is briefly reviewed and is followed by a survey of the research to date on the statistical parallelism of algorithmically generated mathematics items. Results are presented for 8 parallel test forms generated using 16…
White, Desley
2015-01-01
Two practical activities are described, which aim to support critical thinking about statistics as they concern multiple outcomes testing. Formulae are presented in Microsoft Excel spreadsheets, which are used to calculate the inflation of error associated with the quantity of tests performed. This is followed by a decision-making exercise, where…
What Are Null Hypotheses? The Reasoning Linking Scientific and Statistical Hypothesis Testing
Lawson, Anton E.
2008-01-01
We should dispense with use of the confusing term "null hypothesis" in educational research reports. To explain why the term should be dropped, the nature of, and relationship between, scientific and statistical hypothesis testing is clarified by explication of (a) the scientific reasoning used by Gregor Mendel in testing specific…
Steffen, Jason H.; /Fermilab; Ford, Eric B.; /Florida U.; Rowe, Jason F.; /NASA, Ames /SETI Inst., Mtn. View; Fabrycky, Daniel C.; /Lick Observ.; Holman, Matthew J.; /Harvard-Smithsonian Ctr. Astrophys.; Welsh, William F.; /San Diego State U., Astron. Dept.; Borucki, William J.; /NASA, Ames; Batalha, Natalie M.; /San Jose State U.; Bryson, Steve; /NASA, Ames; Caldwell, Douglas A.; /NASA, Ames /SETI Inst., Mtn. View; Ciardi, David R.; /Caltech /NASA, Ames /SETI Inst., Mtn. View
2012-01-01
We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through Quarter six (Q6) 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.
Steffen, Jason H; Rowe, Jason F; Fabrycky, Daniel C; Holman, Matthew J; Welsh, William F; Borucki, William J; Batalha, Natalie M; Bryson, Steve; Caldwell, Douglas A; Ciardi, David R; Jenkins, Jon M; Kjeldsen, Hans; Koch, David G; Prsa, Andrej; Sanderfer, Dwight T; Seader, Shawn; Twicken, Joseph D
2012-01-01
We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through Quarter six (Q6) 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.
Steffen, Jason H. [Fermilab Center for Particle Astrophysics, P.O. Box 500, MS 127, Batavia, IL 60510 (United States); Ford, Eric B. [Astronomy Department, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL 32111 (United States); 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. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Fabrycky, Daniel C. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Holman, Matthew J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Welsh, William F. [Astronomy Department, San Diego State University, San Diego, CA 92182-1221 (United States); Batalha, Natalie M. [Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States); Ciardi, David R. [NASA Exoplanet Science Institute/California Institute of Technology, Pasadena, CA 91125 (United States); Kjeldsen, Hans [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Prsa, Andrej, E-mail: jsteffen@fnal.gov [Department of Astronomy and Astrophysics, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085 (United States)
2012-09-10
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.
Improved Test Planning and Analysis Through the Use of Advanced Statistical Methods
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.
Statistical alignment: computational properties, homology testing and goodness-of-fit
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...... likelihood estimate. In addition, the recursions originally presented by Thorne, Kishino and Felsenstein can be simplified. Two proteins, about 1500 amino acids long, can be analysed with this method in less than five seconds on a fast desktop computer, which makes this method practical for actual data...... 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...
Effect of home testing of international normalized ratio on clinical events.
Matchar, David B; Jacobson, Alan; Dolor, Rowena; Edson, Robert; Uyeda, Lauren; Phibbs, Ciaran S; Vertrees, Julia E; Shih, Mei-Chiung; Holodniy, Mark; Lavori, Philip
2010-10-21
Warfarin anticoagulation reduces thromboembolic complications in patients with atrial fibrillation or mechanical heart valves, but effective management is complex, and the international normalized ratio (INR) is often outside the target range. As compared with venous plasma testing, point-of-care INR measuring devices allow greater testing frequency and patient involvement and may improve clinical outcomes. We randomly assigned 2922 patients who were taking warfarin because of mechanical heart valves or atrial fibrillation and who were competent in the use of point-of-care INR devices to either weekly self-testing at home or monthly high-quality testing in a clinic. The primary end point was the time to a first major event (stroke, major bleeding episode, or death). The patients were followed for 2.0 to 4.75 years, for a total of 8730 patient-years of follow-up. The time to the first primary event was not significantly longer in the self-testing group than in the clinic-testing group (hazard ratio, 0.88; 95% confidence interval, 0.75 to 1.04; P=0.14). The two groups had similar rates of clinical outcomes except that the self-testing group reported more minor bleeding episodes. Over the entire follow-up period, the self-testing group had a small but significant improvement in the percentage of time during which the INR was within the target range (absolute difference between groups, 3.8 percentage points; P<0.001). At 2 years of follow-up, the self-testing group also had a small but significant improvement in patient satisfaction with anticoagulation therapy (P=0.002) and quality of life (P<0.001). As compared with monthly high-quality clinic testing, weekly self-testing did not delay the time to a first stroke, major bleeding episode, or death to the extent suggested by prior studies. These results do not support the superiority of self-testing over clinic testing in reducing the risk of stroke, major bleeding episode, and death among patients taking warfarin
A statistical test on the reliability of the non-coevality of stars in binary systems
Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G.; Degl'Innocenti, S.
2016-03-01
Aims: We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] M⊙, with an initial metallicity [Fe/H] from -0.55 to 0.55 dex, and on stars in the main-sequence phase. Methods: The ages were obtained by means of the SCEPtER technique, a maximum-likelihood procedure relying on a pre-computed grid of stellar models. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. To check the effect of the uncertainties affecting observations on the (non-)coevality assessment, the chosen observational constraints were subjected to a Gaussian perturbation before applying the SCEPtER code. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected in dependence on the mass of the two stars, on the initial metallicity [Fe/H], and on the evolutionary stage of the primary star. Results: The median expected difference in the reconstructed age between the coeval stars of a binary system - caused alone by the observational uncertainties - shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near ZAMS primary. The median difference also shows an increase with the mass of the primary star from 20% for 0.8 M⊙ stars to about 50% for 1.6 M⊙ stars. The reliability of these results was checked by repeating the process with a grid of stellar models computed by a different evolutionary code; the median difference in the critical values was only 0.01. We show that the W test is much more sensible to age differences in the binary system components than the alternative approach of
Green, John; Wheeler, James R
2013-11-15
Solvents are often used to aid test item preparation in aquatic ecotoxicity experiments. This paper discusses the practical, statistical and regulatory considerations. The selection of the appropriate control (if a solvent is used) for statistical analysis is investigated using a database of 141 responses (endpoints) from 71 experiments. The advantages and disadvantages of basing the statistical analysis of treatment effects to the water control alone, solvent control alone, combined controls, or a conditional strategy of combining controls, when not statistically significantly different, are tested. The latter two approaches are shown to have distinct advantages. It is recommended that this approach continue to be the standard used for regulatory and research aquatic ecotoxicology studies. However, wherever technically feasible a solvent should not be employed or at least the concentration minimized. Copyright © 2013 Elsevier B.V. All rights reserved.
Statistical tests for differential expression in cDNA microarray experiments
Cui, Xiangqin; Churchill, Gary A.
2003-01-01
Extracting biological information from microarray data requires appropriate statistical methods. The simplest statistical method for detecting differential expression is the t test, which can be used to compare two conditions when there is replication of samples. With more than two conditions, analysis of variance (ANOVA) can be used, and the mixed ANOVA model is a general and powerful approach for microarray experiments with multiple factors and/or several sources of variation.
Price limits and stock market efficiency: Evidence from rolling bicorrelation test statistic
Lim, Kian-Ping [Labuan School of International Business and Finance, Universiti Malaysia Sabah (Malaysia); Department of Econometrics and Business Statistics, Monash University, P.O. Box 1071, Narre Warren, Victoria 3805 (Australia); Brooks, Robert D. [Department of Econometrics and Business Statistics, Monash University, P.O. Box 1071, Narre Warren, Victoria 3805 (Australia)], E-mail: Robert.brooks@buseco.monash.edu.au
2009-05-15
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.
Statistical studies of animal response data from USF toxicity screening test method
Hilado, C. J.; Machado, A. M.
1978-01-01
Statistical examination of animal response data obtained using Procedure B of the USF toxicity screening test method indicates that the data deviate only slightly from a normal or Gaussian distribution. This slight departure from normality is not expected to invalidate conclusions based on theoretical statistics. Comparison of times to staggering, convulsions, collapse, and death as endpoints shows that time to death appears to be the most reliable endpoint because it offers the lowest probability of missed observations and premature judgements.
Theory, Methods and Tools for Statistical Testing of Pseudo and Quantum Random Number Generators
Jakobsson, Krister Sune
2014-01-01
Statistical random number testing is a well studied field focusing on pseudo-random number generators, that is to say algorithms that produce random-looking sequences of numbers. These generators tend to have certain kinds of flaws, which have been exploited through rigorous testing. Such testing has led to advancements, and today pseudo random number generators are both very high-speed and produce seemingly random numbers. Recent advancements in quantum physics have opened up new doors, wher...
Humenik, K. (Maryland Univ., Baltimore, MD (USA)); Gross, K.C. (Argonne National Lab., IL (USA))
1989-11-09
This paper examines the properties of sequential probability ratio tests (SPRT's) and the application of these tests to nuclear power reactor operation. Recently SPRT's have been applied to delayed-neutron (DN) signal data analysis using actual reactor data from the Experimental Breeder Reactor-II, which is operated by Argonne National Laboratory. The implementation of this research as part of an expert system is described. Mathematical properties of the SPRT are investigated, and theoretical results are validated with tests that use DN-signal data taken from the EBR-II in Idaho. Variations of the basic SPRT and applications to general signal validation are also explored. 16 refs., 3 figs.
Tests of Full-Scale Helicopter Rotors at High Advancing Tip Mach Numbers and Advance Ratios
Biggers, James C.; McCloud, John L., III; Stroub, Robert H.
2015-01-01
As a continuation of the studies of reference 1, three full-scale helicopter rotors have been tested in the Ames Research Center 40- by SO-foot wind tunnel. All three of them were two-bladed, teetering rotors. One of the rotors incorporated the NACA 0012 airfoil section over the entire length of the blade. This rotor was tested at advance ratios up to 1.05. Both of the other rotors were tapered in thickness and incorporated leading-edge camber over the outer 20 percent of the blade radius. The larger of these rotors was tested at advancing tip Mach numbers up to 1.02. Data were obtained for a wide range of lift and propulsive force, and are presented without discussion.
A test procedure for determining the influence of stress ratio on fatigue crack growth
Fitzgerald, J. H.; Wei, R. P.
1974-01-01
A test procedure is outlined by which the rate of fatigue crack growth over a range of stress ratios and stress intensities can be determined expeditiously using a small number of specimens. This procedure was developed to avoid or circumvent the effects of load interactions on fatigue crack growth, and was used to develop data on a mill annealed Ti-6Al-4V alloy plate. Experimental data suggest that the rates of fatigue crack growth among the various stress ratios may be correlated in terms of an effective stress intensity range at given values of K max. This procedure is not to be used, however, for determining the corrosion fatigue crack growth characteristics of alloys when nonsteady-state effects are significant.
Computational design of low aspect ratio wing-winglets for transonic wind-tunnel testing
Kuhlman, John M.; Brown, Christopher K.
1989-01-01
A computational design has been performed for three different low aspect ratio wing planforms fitted with nonplanar winglets; one of the three planforms has been selected to be constructed as a wind tunnel model for testing in the NASA LaRC 7 x 10 High Speed Wind Tunnel. A design point of M = 0.8, CL approx = 0.3 was selected, for wings of aspect ratio equal to 2.2, and leading edge sweep angles of 45 and 50 deg. Winglet length is 15 percent of the wing semispan, with a cant angle of 15 deg, and a leading edge sweep of 50 deg. Winglet total area equals 2.25 percent of the wing reference area. This report summarizes the design process and the predicted transonic performance for each configuration.
GNSS spoofing detection: Theoretical analysis and performance of the Ratio Test metric in open sky
Jie Huang
2016-03-01
Full Text Available Nowadays more and more applications rely on the information provided by Global Navigation Satellite Systems (GNSSs, but the vulnerability of GNSS signals to interference, jamming and spoofing is a growing concern. Among all the possible sources of intentional interference, spoofing is extremely deceptive and sinister. In fact, the victim receiver may not be able to warn the user and discern between authentic and false signals. For this reason, a receiver featuring spoofing detection capabilities might become a need in many cases. Different types of spoofing detection algorithms have been presented in recent literature. One of the first, referred to as Ratio Metric, allows for the monitoring of possible distortions in the signal correlation. The effectiveness of the Ratio Test has been widely discussed and demonstrated, while in this paper we analyze its performance, proposing a mathematical model that is used to assess the false alarm and detection probabilities.
t-tests, non-parametric tests, and large studies—a paradox of statistical practice?
Fagerland Morten W
2012-06-01
Full Text Available Abstract Background During the last 30 years, the median sample size of research studies published in high-impact medical journals has increased manyfold, while the use of non-parametric tests has increased at the expense of t-tests. This paper explores this paradoxical practice and illustrates its consequences. Methods A simulation study is used to compare the rejection rates of the Wilcoxon-Mann-Whitney (WMW test and the two-sample t-test for increasing sample size. Samples are drawn from skewed distributions with equal means and medians but with a small difference in spread. A hypothetical case study is used for illustration and motivation. Results The WMW test produces, on average, smaller p-values than the t-test. This discrepancy increases with increasing sample size, skewness, and difference in spread. For heavily skewed data, the proportion of p Conclusions Non-parametric tests are most useful for small studies. Using non-parametric tests in large studies may provide answers to the wrong question, thus confusing readers. For studies with a large sample size, t-tests and their corresponding confidence intervals can and should be used even for heavily skewed data.
A Test of Carbon and Oxygen Stable Isotope Ratio Process Models in Tree Rings.
Roden, J. S.; Farquhar, G. D.
2008-12-01
Stable isotopes ratios of carbon and oxygen in tree ring cellulose have been used to infer environmental change. Process-based models have been developed to clarify the potential of historic tree ring records for meaningful paleoclimatic reconstructions. However, isotopic variation can be influenced by multiple environmental factors making simplistic interpretations problematic. Recently, the dual isotope approach, where the variation in one stable isotope ratio (e.g. oxygen) is used to constrain the interpretation of variation in another (e.g. carbon), has been shown to have the potential to de-convolute isotopic analysis. However, this approach requires further testing to determine its applicability for paleo-reconstructions using tree-ring time series. We present a study where the information needed to parameterize mechanistic models for both carbon and oxygen stable isotope ratios were collected in controlled environment chambers for two species (Pinus radiata and Eucalyptus globulus). The seedlings were exposed to treatments designed to modify leaf temperature, transpiration rates, stomatal conductance and photosynthetic capacity. Both species were grown for over 100 days under two humidity regimes that differed by 20%. Stomatal conductance was significantly different between species and for seedlings under drought conditions but not between other treatments or humidity regimes. The treatments produced large differences in transpiration rate and photosynthesis. Treatments that effected photosynthetic rates but not stomatal conductance influenced carbon isotope discrimination more than those that influenced primarily conductance. The various treatments produced a range in oxygen isotope ratios of 7 ‰. Process models predicted greater oxygen isotope enrichment in tree ring cellulose than observed. The oxygen isotope ratios of bulk leaf water were reasonably well predicted by current steady-state models. However, the fractional difference between models that
[Tests of statistical significance in three biomedical journals: a critical review].
Sarria Castro, Madelaine; Silva Ayçaguer, Luis Carlos
2004-05-01
To describe the use of conventional tests of statistical significance and the current trends shown by their use in three biomedical journals read in Spanish-speaking countries. All descriptive or explanatory original articles published in the five-year period of 1996 through 2000 were reviewed in three journals: Revista Cubana de Medicina General Integral [Cuban Journal of Comprehensive General Medicine], Revista Panamericana de Salud Pública/Pan American Journal of Public Health, and Medicina Clínica [Clinical Medicine] (which is published in Spain). In the three journals that were reviewed various shortcomings were found in their use of hypothesis tests based on P values and in the limited use of new tools that have been suggested for use in their place: confidence intervals (CIs) and Bayesian inference. The basic findings of our research were: minimal use of CIs, as either a complement to significance tests or as the only statistical tool; mentions of a small sample size as a possible explanation for the lack of statistical significance; a predominant use of rigid alpha values; a lack of uniformity in the presentation of results; and improper reference in the research conclusions to the results of hypothesis tests. Our results indicate the lack of compliance by authors and editors with accepted standards for the use of tests of statistical significance. The findings also highlight that the stagnant use of these tests continues to be a common practice in the scientific literature.
Statistical tests of conditional independence between responses and/or response times on test items
van der Linden, Willem J.; Glas, Cornelis A.W.
2010-01-01
Three plausible assumptions of conditional independence in a hierarchical model for responses and response times on test items are identified. For each of the assumptions, a Lagrange multiplier test of the null hypothesis of conditional independence against a parametric alternative is derived. The t
shahriar Azizi
2013-09-01
Full Text Available Recent years marketing theories has been developed increasingly. This development needs paying attention to variables such as: moderator and mediator for extending marketing research models. Marketing and management researchers need to be informed about the meaning of mediator, moderator and intervening variables and accurate statistical procedures and tests for identification. By understanding the true meaning of mediator, moderator and intervening variables, providing more accurate marketing models that fits real word become easier. In this paper the meanings of those variables were presented and compared. In the next sections of the paper, statistical procedures and tests provided.
A new model test in high energy physics in frequentist and Bayesian statistical formalisms
Kamenshchikov, Andrey
2016-01-01
A problem of a new physical model test given observed experimental data is a typical one for modern experiments of high energy physics (HEP). A solution of the problem may be provided with two alternative statistical formalisms, namely frequentist and Bayesian, which are widely spread in contemporary HEP searches. A characteristic experimental situation is modeled from general considerations and both the approaches are utilized in order to test a new model. The results are juxtaposed, what demonstrates their consistency in this work. An effect of a systematic uncertainty treatment in the statistical analysis is also considered.
A new model test in high energy physics in frequentist and Bayesian statistical formalisms
Kamenshchikov, A.
2017-01-01
A problem of a new physical model test given observed experimental data is a typical one for modern experiments of high energy physics (HEP). A solution of the problem may be provided with two alternative statistical formalisms, namely frequentist and Bayesian, which are widely spread in contemporary HEP searches. A characteristic experimental situation is modeled from general considerations and both the approaches are utilized in order to test a new model. The results are juxtaposed, what demonstrates their consistency in this work. An effect of a systematic uncertainty treatment in the statistical analysis is also considered.
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 Ranking....... By use of statistical power analyses and demonstration of effect sizes, we emphasize that importance of empirical findings lies in “differences that make a difference” and not statistical significance tests per se. Finally we discuss the crucial assumption of randomness and question the presumption...... that randomness is present in the university ranking data. We conclude that the application of statistical significance tests in relation to university rankings, as recently advocated, is problematic and can be misleading....
Homogeneity and change-point detection tests for multivariate data using rank statistics
Lung-Yut-Fong, Alexandre; Cappé, Olivier
2011-01-01
Detecting and locating changes in highly multivariate data is a major concern in several current statistical applications. In this context, the first contribution of the paper is a novel non-parametric two-sample homogeneity test for multivariate data based on the well-known Wilcoxon rank statistic. The proposed two-sample homogeneity test statistic can be extended to deal with ordinal or censored data as well as to test for the homogeneity of more than two samples. The second contribution of the paper concerns the use of the proposed test statistic to perform retrospective change-point analysis. It is first shown that the approach is computationally feasible even when looking for a large number of change-points thanks to the use of dynamic programming. Computable asymptotic $p$-values for the test are then provided in the case where a single potential change-point is to be detected. Compared to available alternatives, the proposed approach appears to be very reliable and robust. This is particularly true in ...
The Likelihood Ratio Test of Common Factors under Non-Ideal Conditions
Ana M. Angulo
2011-01-01
Full Text Available El modelo espacial de Durbin ocupa una posición interesante en econometría espacial. Es la forma reducida de un modelo de corte transversal con dependencia en los errores y puede ser utilizado como ecuación de anidación en un enfoque más general de selección de modelos. En concreto, a partir de esta ecuación puede obtenerse el Ratio de Verosimilitudes conocido como test de Factores Comunes (LRCOM. Como se muestra en Mur y Angulo (2006, este test tiene buenas propiedades si el modelo está correctamente especificado. Sin embargo, por lo que sabemos, no hay referencias en la literatura sobre el comportamiento de este test bajo condiciones no ideales. En concreto, estudiamos el comportamiento del test en los casos de heterocedasticidad, no normalidad, endogeneidad, matrices de contactos densas y no-linealidad. Nuestros resultados ofrecen una visión positiva del test de Factores Comunes que parece una técnica útil en el instrumental propio de la econometría espacial contemporánea.
Xu, Xu Steven; Yuan, Min; Yang, Haitao; Feng, Yan; Xu, Jinfeng; Pinheiro, Jose
2017-01-01
Covariate analysis based on population pharmacokinetics (PPK) is used to identify clinically relevant factors. The likelihood ratio test (LRT) based on nonlinear mixed effect model fits is currently recommended for covariate identification, whereas individual empirical Bayesian estimates (EBEs) are considered unreliable due to the presence of shrinkage. The objectives of this research were to investigate the type I error for LRT and EBE approaches, to confirm the similarity of power between the LRT and EBE approaches from a previous report and to explore the influence of shrinkage on LRT and EBE inferences. Using an oral one-compartment PK model with a single covariate impacting on clearance, we conducted a wide range of simulations according to a two-way factorial design. The results revealed that the EBE-based regression not only provided almost identical power for detecting a covariate effect, but also controlled the false positive rate better than the LRT approach. Shrinkage of EBEs is likely not the root cause for decrease in power or inflated false positive rate although the size of the covariate effect tends to be underestimated at high shrinkage. In summary, contrary to the current recommendations, EBEs may be a better choice for statistical tests in PPK covariate analysis compared to LRT. We proposed a three-step covariate modeling approach for population PK analysis to utilize the advantages of EBEs while overcoming their shortcomings, which allows not only markedly reducing the run time for population PK analysis, but also providing more accurate covariate tests.
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.
Gust response analysis and wind tunnel test for a high-aspect ratio wing
Liu Yi
2016-02-01
Full Text Available A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisciplinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter boundary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quantitative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flexible wings.
Bertram, Erik; Banerjee, Robi; Klessen, Ralf S
2011-01-01
We study the mass-to-flux ratio (M/\\Phi) of clumps and cores in simulations of supersonic, magnetohydrodynamical turbulence for different initial magnetic field strengths. We investigate whether the (M/\\Phi)-ratio of core and envelope, R = (M/\\Phi)_{core}/(M/\\Phi)_{envelope} can be used to distinguish between theories of ambipolar diffusion and turbulence-regulated star formation. We analyse R for different Lines-of-Sight (LoS) in various sub-cubes of our simulation box. We find that, 1) the average and median values of |R| for different times and initial magnetic field strengths are typically greater, but close to unity, 2) the average and median values of |R| saturate at average values of |R| ~ 1 for smaller magnetic fields, 3) values of |R| < 1 for small magnetic fields in the envelope are caused by field reversals when turbulence twists the field lines such that field components in different directions average out. Finally, we propose two mechanisms for generating values |R| ~< 1 for the weak and st...
Statistical Tests for the Gaussian Nature of Primordial Fluctuations Through CBR Experiments
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 the Hotelling's $T^{2}$ statistic defined through bispectral estimates of a one dimensional dataset. The effect of noise present in the current data is discussed in detail and the COBE 53 GHz dataset is analyzed. Our analysis shows that, on the large...
An Algorithm to Improve Test Answer Copying Detection Using the Omega Statistic
Maeda, Hotaka; Zhang, Bo
2017-01-01
The omega (?) statistic is reputed to be one of the best indices for detecting answer copying on multiple choice tests, but its performance relies on the accurate estimation of copier ability, which is challenging because responses from the copiers may have been contaminated. We propose an algorithm that aims to identify and delete the suspected…
Statistical methods for the detection of answer copying on achievement tests
Sotaridona, Leonardo Sitchirita
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 characteristi
Interpreting Statistical Significance Test Results: A Proposed New "What If" Method.
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…
Recent Literature on Whether Statistical Significance Tests Should or Should Not Be Banned.
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…
Bettonvil, B.W.M.; Del Castillo, E.; Kleijnen, J.P.C.
2007-01-01
This paper studies simulation-based optimization with multiple outputs. It assumes that the simulation model has one random objective function and must satisfy given constraints on the other random outputs. It presents a statistical procedure for test- ing whether a specific input combination
Bettonvil, B.W.M.; Del Castillo, E.; Kleijnen, J.P.C.
2007-01-01
This paper studies simulation-based optimization with multiple outputs. It assumes that the simulation model has one random objective function and must satisfy given constraints on the other random outputs. It presents a statistical procedure for test- ing whether a specific input combination (propo
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...
Connecting Science and Mathematics: The Nature of Scientific and Statistical Hypothesis Testing
Lawson, Anton E.; Oehrtman, Michael; Jensen, Jamie
2008-01-01
Confusion persists concerning the roles played by scientific hypotheses and predictions in doing science. This confusion extends to the nature of scientific and statistical hypothesis testing. The present paper utilizes the "If/and/then/Therefore" pattern of hypothetico-deductive (HD) reasoning to explicate the nature of both scientific and…
Bonnice, W. F.; Motyka, P.; Wagner, E.; Hall, S. R.
1986-01-01
The performance of the orthogonal series generalized likelihood ratio (OSGLR) test in detecting and isolating commercial aircraft control surface and actuator failures is evaluated. A modification to incorporate age-weighting which significantly reduces the sensitivity of the algorithm to modeling errors is presented. The steady-state implementation of the algorithm based on a single linear model valid for a cruise flight condition is tested using a nonlinear aircraft simulation. A number of off-nominal no-failure flight conditions including maneuvers, nonzero flap deflections, different turbulence levels and steady winds were tested. Based on the no-failure decision functions produced by off-nominal flight conditions, the failure detection and isolation performance at the nominal flight condition was determined. The extension of the algorithm to a wider flight envelope by scheduling on dynamic pressure and flap deflection is examined. Based on this testing, the OSGLR algorithm should be capable of detecting control surface failures that would affect the safe operation of a commercial aircraft. Isolation may be difficult if there are several surfaces which produce similar effects on the aircraft. Extending the algorithm over the entire operating envelope of a commercial aircraft appears feasible.
Shah, Syed Ghulam Sarwar; Barnett, Julie; Kuljis, Jasna; Hone, Kate; Kaczmarski, Richard
2013-01-01
Purpose To identify factors that determine patients’ intentions to use point-of-care medical devices, ie, portable coagulometer devices for self-testing of the international normalized ratio (INR) required for ongoing monitoring of blood-coagulation intensity among patients on long-term oral anticoagulation therapy with vitamin K antagonists, eg, warfarin. Methods A cross-sectional study that applied the technology-acceptance model through a self-completed questionnaire, which was administered to a convenience sample of 125 outpatients attending outpatient anticoagulation services at a district general hospital in London, UK. Data were analyzed using descriptive statistics, factor analyses, and structural equation modeling. Results The participants were mainly male (64%) and aged ≥ 71 years (60%). All these patients were attending the hospital outpatient anticoagulation clinic for INR testing; only two patients were currently using INR self-testing, 84% of patients had no knowledge about INR self-testing using a portable coagulometer device, and 96% of patients were never offered the option of the INR self-testing. A significant structural equation model explaining 79% of the variance in patients’ intentions to use INR self-testing was observed. The significant predictors that directly affected patients’ intention to use INR self-testing were the perception of technology (β = 0.92, P < 0.001), trust in doctor (β = −0.24, P = 0.028), and affordability (β = 0.15, P = 0.016). In addition, the perception of technology was significantly affected by trust in doctor (β = 0.43, P = 0.002), age (β = −0.32, P < 0.001), and affordability (β = 0.23, P = 0.013); thereby, the intention to use INR self-testing was indirectly affected by trust in doctor (β = 0.40), age (β = −0.29), and affordability (β = 0.21) via the perception of technology. Conclusion Patients’ intentions to use portable coagulometers for INR self-testing are affected by patients
Sommer, Helle Mølgaard; Holst, Helle; Spliid, Henrik;
1995-01-01
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....
International normalized ratio self-testing and self-management: improving patient outcomes
Pozzi M
2016-10-01
Full Text Available Matteo Pozzi,1 Julia Mitchell,2 Anna Maria Henaine,3 Najib Hanna,4 Ola Safi,4 Roland Henaine2 1Department of Adult Cardiac Surgery, “Louis Pradel” Cardiologic Hospital, Lyon, France; 2Department of Congenital Cardiac Surgery, “Louis Pradel” Cardiologic Hospital, Lyon, France; 3Clinical Pharmacology Unit, Lebanese University, Beirut, Lebanon; 4Pediatric Unit, “Hotel Dieu de France” Hospital, Saint Joseph University, Beirut, Lebanon Abstract: Long term oral anti-coagulation with vitamin K antagonists is a risk factor of hemorrhagic or thromebomlic complications. Periodic laboratory testing of international normalized ratio (INR and a subsequent dose adjustment are therefore mandatory. The use of home testing devices to measure INR has been suggested as a potential way to improve the comfort and compliance of the patients and their families, the frequency of monitoring and, finally, the management and safety of long-term oral anticoagulation. In pediatric patients, increased doses to obtain and maintain the therapeutic target INR, more frequent adjustments and INR testing, multiple medication, inconstant nutritional intake, difficult venepunctures, and the need to go to the laboratory for testing (interruption of school and parents’ work attendance highlight those difficulties. After reviewing the most relevant published studies of self-testing and self-management of INR for adult patients and children on oral anticoagulation, it seems that these are valuable and effective strategies of INR control. Despite an unclear relationship between INR control and clinical effects, these self-strategies provide a better control of the anticoagulant effect, improve patients and their family quality of life, and are an appealing solution in term of cost-effectiveness. Structured education and knowledge evaluation by trained health care professionals is required for children, to be able to adjust their dose treatment safely and accurately. However
Hamilton, Diana A.; Mahoney, Martin C.; Novalen, Maria; Chenoweth, Meghan J.; Heitjan, Daniel F.; Lerman, Caryn; Tyndale, Rachel F.
2015-01-01
Introduction: The nicotine metabolite ratio (NMR), the ratio of 3-hydroxycotinine to cotinine, is a biomarker used in smoking cessation research, with several retrospective studies suggesting that NMR predicts treatment outcome. To be maximally useful in tailoring treatment, estimates of NMR should be stable over time. The present study is the first to examine the short-term test-retest reliability of NMR among treatment-seeking smokers. Methods: Blood NMR was assessed at two time points, approximately 2–3 weeks apart and prior to intervention, among 72 healthy adult smokers (49% female; 35% non-White) enrolled in a cessation trial (http://ClinicalTrials.gov ID: NCT01314001). Results: Mean NMR was stable from Time-1 to Time-2, with no significant change between assessments; test-retest reliability for NMR values was excellent (ICC[2,1] = 0.87). Test-retest reliability remained acceptable to high when NMR was categorized, as in recent clinical trials. Classification of participants as slow (quartile 1, NMR ≤ 0.24) or normal/fast NMR (quartiles 2–4, NMR ≥ 0.25) was consistent from Time-1 to Time-2 for 96% of participants (κ = 0.89). Though classification of participants into NMR quartiles was less consistent from Time-1 to Time-2 (67% agreement; weighted κ = 0.73), all reclassifications occurred between adjacent quartiles. Conclusions: Overall, these data support the use of a single NMR assessment for association studies with smoking phenotypes and in smokers seeking to quit, and they encourage large-scale efforts to determine optimal NMR cutpoints for tailoring treatment selection. PMID:25732567
Reproducibility-optimized test statistic for ranking genes in microarray studies.
Elo, Laura L; Filén, Sanna; Lahesmaa, Riitta; Aittokallio, Tero
2008-01-01
A principal goal of microarray studies is to identify the genes showing differential expression under distinct conditions. In such studies, the selection of an optimal test statistic is a crucial challenge, which depends on the type and amount of data under analysis. While previous studies on simulated or spike-in datasets do not provide practical guidance on how to choose the best method for a given real dataset, we introduce an enhanced reproducibility-optimization procedure, which enables the selection of a suitable gene- anking statistic directly from the data. In comparison with existing ranking methods, the reproducibilityoptimized statistic shows good performance consistently under various simulated conditions and on Affymetrix spike-in dataset. Further, the feasibility of the novel statistic is confirmed in a practical research setting using data from an in-house cDNA microarray study of asthma-related gene expression changes. These results suggest that the procedure facilitates the selection of an appropriate test statistic for a given dataset without relying on a priori assumptions, which may bias the findings and their interpretation. Moreover, the general reproducibilityoptimization procedure is not limited to detecting differential expression only but could be extended to a wide range of other applications as well.
Azim Honarmand; Mohammadreza Safavi; Ahmad Yaraghi; Mohammadali Attari; Mehdi Khazaei; Majid Zamani
2015-01-01
Background: Preoperative airway assessment tests have been presented to help in anticipating a difficult airway. We conducted this study to compare five methods in prediction of difficult laryngoscopy: Neck circumference (NC), NC to thyromental distance ratio (NC/TMD), the ratio of height to thyromental distance (RHTMD), upper lip bite test (ULBT) and Mallampati test (MMT). These five methods are the most commonly used ones and have different powers for it. It was not clear which of these met...
Luyan Zhang; Huihui Li; Jiankang Wang
2012-01-01
Epistasis is a commonly observed genetic phenomenon and an important source of variation of complex traits,which could maintain additive variance and therefore assure the long-term genetic gain in breeding.Inclusive composite interval mapping (ICIM) is able to identify epistatic quantitative trait loci (QTLs) no matter whether the two interacting QTLs have any additive effects.In this article,we conducted a simulation study to evaluate detection power and false discovery rate (FDR) of ICIM epistatic mapping,by considering F2 and doubled haploid (DH) populations,different F2 segregation ratios and population sizes.Results indicated that estimations of QTL locations and effects were unbiased,and the detection power of epistatic mapping was largely affected by population size,heritability of epistasis,and the amount and distribution of genetic effects.When the same likelihood of odd (LOD) threshold was used,detection power of QTL was higher in F2 population than power in DH population; meanwhile FDR in F2 was also higher than that in DH.The increase of marker density from 10 cM to 5 cM led to similar detection power but higher FDR.In simulated populations,ICIM achieved better mapping results than multiple interval mapping (MIM) in estimation of QTL positions and effect.At the end,we gave epistatic mapping results of ICIM in one actual population in rice (Oryza sativa L.).
Direct Numerical Test of the Statistical Mechanical Theory of Hydrophobic Interactions
Chaudhari, M I; Ashbaugh, H S; Pratt, L R
2013-01-01
This work tests the statistical mechanical theory of hydrophobic interactions, isolates consequences of excluded volume interactions, and obtains B2 for those purposes. Cavity methods that are particularly appropriate for study of hydrophobic interactions between atomic-size hard spheres in liquid water are developed and applied to test aspects of the Pratt-Chandler (PC) theory that have not been tested. Contact hydrophobic interactions between Ar-size hard-spheres in water are significantly more attractive than predicted by the PC theory. The corresponding results for the osmotic second virial coefficient are attractive (B2 <0), and more attractive with increasing temperature (Delta B2/Delta T < 0) in the temperature range 300K < T < 360K. This information has not been available previously, but is essential for development of the molecular-scale statistical mechanical theory of hydrophobic interactions, particularly for better definition of the role of attractive intermolecular interactions assoc...
Boonstra, Philip S; Gruber, Stephen B; Raymond, Victoria M
2010-01-01
, 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......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...... to a recently proposed random effects model which includes extended pedigree data and unaffected family members [Larsen et al., 2009]. A naive use of the paired t-test is biased for the simple reason that age of onset has to be less than the age at ascertainment (interview) for both affected parent and child...
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...... to a recently proposed random effects model which includes extended pedigree data and unaffected family members [Larsen et al., 2009]. A naive use of the paired t-test is biased for the simple reason that age of onset has to be less than the age at ascertainment (interview) for both affected parent and child...
Vexler, Albert; Kim, Young Min; Yu, Jihnhee; Lazar, Nicole A; Hutson, Aland
2014-12-01
Various exact tests for statistical inference are available for powerful and accurate decision rules provided that corresponding critical values are tabulated or evaluated via Monte Carlo methods. This article introduces a novel hybrid method for computing p-values of exact tests by combining Monte Carlo simulations and statistical tables generated a priori. To use the data from Monte Carlo generations and tabulated critical values jointly, we employ kernel density estimation within Bayesian-type procedures. The p-values are linked to the posterior means of quantiles. In this framework, we present relevant information from the Monte Carlo experiments via likelihood-type functions, whereas tabulated critical values are used to reflect prior distributions. The local maximum likelihood technique is employed to compute functional forms of prior distributions from statistical tables. Empirical likelihood functions are proposed to replace parametric likelihood functions within the structure of the posterior mean calculations to provide a Bayesian-type procedure with a distribution-free set of assumptions. We derive the asymptotic properties of the proposed nonparametric posterior means of quantiles process. Using the theoretical propositions, we calculate the minimum number of needed Monte Carlo resamples for desired level of accuracy on the basis of distances between actual data characteristics (e.g. sample sizes) and characteristics of data used to present corresponding critical values in a table. The proposed approach makes practical applications of exact tests simple and rapid. Implementations of the proposed technique are easily carried out via the recently developed STATA and R statistical packages.
Rudd, James; Moore, Jason H; Urbanowicz, Ryan J
2013-11-01
Permutation-based statistics for evaluating the significance of class prediction, predictive attributes, and patterns of association have only appeared within the learning classifier system (LCS) literature since 2012. While still not widely utilized by the LCS research community, formal evaluations of test statistic confidence are imperative to large and complex real world applications such as genetic epidemiology where it is standard practice to quantify the likelihood that a seemingly meaningful statistic could have been obtained purely by chance. LCS algorithms are relatively computationally expensive on their own. The compounding requirements for generating permutation-based statistics may be a limiting factor for some researchers interested in applying LCS algorithms to real world problems. Technology has made LCS parallelization strategies more accessible and thus more popular in recent years. In the present study we examine the benefits of externally parallelizing a series of independent LCS runs such that permutation testing with cross validation becomes more feasible to complete on a single multi-core workstation. We test our python implementation of this strategy in the context of a simulated complex genetic epidemiological data mining problem. Our evaluations indicate that as long as the number of concurrent processes does not exceed the number of CPU cores, the speedup achieved is approximately linear.
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...
A Test by Any Other Name: P Values, Bayes Factors, and Statistical Inference.
Stern, Hal S
2016-01-01
Procedures used for statistical inference are receiving increased scrutiny as the scientific community studies the factors associated with insuring reproducible research. This note addresses recent negative attention directed at p values, the relationship of confidence intervals and tests, and the role of Bayesian inference and Bayes factors, with an eye toward better understanding these different strategies for statistical inference. We argue that researchers and data analysts too often resort to binary decisions (e.g., whether to reject or accept the null hypothesis) in settings where this may not be required.
Statistical power analysis a simple and general model for traditional and modern hypothesis tests
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
Halpin, Peter F; Stam, Henderikus J
2006-01-01
The application of statistical testing in psychological research over the period of 1940-1960 is examined in order to address psychologists' reconciliation of the extant controversy between the Fisher and Neyman-Pearson approaches. Textbooks of psychological statistics and the psychological journal literature are reviewed to examine the presence of what Gigerenzer (1993) called a hybrid model of statistical testing. Such a model is present in the textbooks, although the mathematically incomplete character of this model precludes the appearance of a similarly hybridized approach to statistical testing in the research literature. The implications of this hybrid model for psychological research and the statistical testing controversy are discussed.
Atomic bomb testing and its effects on global male to female ratios at birth.
Grech, Victor
2015-01-01
Fallout from atomic bomb testing may travel great distances before precipitating. Males are born in excess of females in a ratio that approximates 0.515 (M/T: male live births divided by total live births. Radiation increases M/T by causing lethal malformations that affect female more than male foetuses, decreasing total births. This study was carried out in order to ascertain whether the effects of increased background radiation levels from atomic weapon testing had any widespread effects on M/T and births in the Americas, Europe, Asia and Australasia in relation to the Partial Test Ban Treaty of 1963. Annual live births by gender were obtained from a World Health Organization dataset and annual number of atomic bomb tests were also obtained (historical data). Overall, 94.5% of births studied showed a uniform reduction in M/T between the early 1950s to the late 1960s, followed by an increase to the mid-1970s, with a subsequent decline. A negative correlation of M/T with total births was found in 66% of births studied, and these were the regions which exhibited the rising M/T pattern in the 1970s. The birth deficit for countries with significant correlations of total births with M/T (North America, Europe and Asia) was estimated at 10090701. A rising M/T was found in most regions in temporal association with atomic weapon testing. Most of these regions also had an associated decline in total births. Elevated levels of man-made ambient radiation may have reduced total births, affecting pregnancies carrying female pregnancies more than those carrying male pregnancies, thereby skewing M/T toward a higher male proportion.
Bel, Julien; Marinoni, Christian; Valageas, Patrick
2014-01-01
The clustering ratio $\\eta$, a large-scale structure observable originally devised to constrain the shape of the power spectrum of matter density fluctuations, is shown to provide a sensitive and model independent probe of the nature of gravity in the cosmological regime. We apply this analysis to $F(R)$ theories of gravity using the luminous red galaxy sample extracted from the Sloan Digital Sky Survey. We find that the absolute amplitude of deviations from GR, $f_{R_0 }$, is constrained to be smaller than $3 \\times 10^{-6}$ at the 1$\\sigma$ confidence level. This bound, improving by an order of magnitude on current constraints, makes cosmological probes of gravity competitive with Solar system tests.
AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS
Singal, J.; Jones, E.; Dunlap, H. [Physics Department, University of Richmond 28 Westhampton Way, Richmond, VA 23173 (United States); Kogut, A., E-mail: jsingal@richmond.edu [Code 665, NASA Goddard Space Flight Center Greenbelt, MD 20771 (United States)
2015-01-20
We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)
Sakievich, Philip; Peet, Yulia; Adrian, Ronald
2016-11-01
At high Rayleigh numbers in moderate aspect-ratio cylindrical domains turbulent Rayleigh-Bénard convection (RBC) exhibits coherent large-scale motions with patterns like some of those found in laminar flow. In this work we show how the patterns of the largest scales in turbulent RBC affect the bias and convergence of the flow statistics at aspect-ratio 6.3 (diameter/ height). Large scale motions influence two of the finite-time statistical mean's inherent properties: 1) the orientation of the patterns changes so slowly that it may appear almost fixed during a finite averaging time interval, thereby imbedding a preferred azimuthal direction in the sampled data; 2) they also have at least two states associated with the occurrence of up and down motions near the center of the convection cell. We will present a novel technique for triggering additional states of RBC in DNS simulations that are targeted for improving the statistical convergence of the flow. This technique gently perturbs the flow so that the new variations of the large scale patterns can be sampled. Funding through U. S. National Science Foundation Grants CBET-1335731, CMMI-1250124 and XSEDE research allocation TG-CTS150039.
A Cooperative Test of the Load/Unload Response Ratio Proposed Method of Earthquake Prediction
Trotta, J. E.; Tullis, T. E.
2004-12-01
The Load/Unload Response Ratio (LURR) method is a proposed technique to predict earthquakes that was first put forward by Yin in 1984 (Yin, 1987). LURR is based on the idea that when a region is near failure, there is an increase in the rate of seismic activity during loading of the tidal cycle relative to the rate of seismic activity during unloading of the tidal cycle. Typically the numerator of the LURR ratio is the number, or the sum of some measure of the size (e.g. Benioff strain), of small earthquakes that occur during loading of the tidal cycle, whereas the denominator is the same as the numerator except it is calculated during unloading. LURR method suggests this ratio should increase in the months to year preceding a large earthquake. Regions near failure have tectonic stresses nearly high enough for a large earthquake to occur, thus it seems more likely that smaller earthquakes in the region would be triggered when the tidal stresses add to the tectonic ones. However, until recently even the most careful studies suggested that the effect of tidal stresses on earthquake occurrence is very small and difficult to detect. New studies have shown that there is a tidal triggering effect on shallow thrust faults in areas with strong tides from ocean loading (Tanaka et al., 2002; Cochran et al., 2004). We have been conducting an independent test of the LURR method, since there would be important scientific and social implications if the LURR method were proven to be a robust method of earthquake prediction. Smith and Sammis (2003) also undertook a similar study. Following both the parameters of Yin et al. (2000) and the somewhat different ones of Smith and Sammis (2003), we have repeated calculations of LURR for the Northridge and Loma Prieta earthquakes in California. Though we have followed both sets of parameters closely, we have been unable to reproduce either set of results. A general agreement was made at the recent ACES Workshop in China between research
An Adaptive Association Test for Multiple Phenotypes with GWAS Summary Statistics.
Kim, Junghi; Bai, Yun; Pan, Wei
2015-12-01
We study the problem of testing for single marker-multiple phenotype associations based on genome-wide association study (GWAS) summary statistics without access to individual-level genotype and phenotype data. For most published GWASs, because obtaining summary data is substantially easier than accessing individual-level phenotype and genotype data, while often multiple correlated traits have been collected, the problem studied here has become increasingly important. We propose a powerful adaptive test and compare its performance with some existing tests. We illustrate its applications to analyses of a meta-analyzed GWAS dataset with three blood lipid traits and another with sex-stratified anthropometric traits, and further demonstrate its potential power gain over some existing methods through realistic simulation studies. We start from the situation with only one set of (possibly meta-analyzed) genome-wide summary statistics, then extend the method to meta-analysis of multiple sets of genome-wide summary statistics, each from one GWAS. We expect the proposed test to be useful in practice as more powerful than or complementary to existing methods.
Role of Statistical tests in Estimation of the Security of a New Encryption Algorithm
Krishna, Addepalli V N
2010-01-01
Encryption study basically deals with three levels of algorithms. The first algorithm deals with encryption mechanism, second deals with decryption Mechanism and the third discusses about the generation of keys and sub keys used in the encryption study. In the given study, a new algorithm is discussed. The algorithm executes a series of steps and generates a sequence. This sequence is being used as sub key to be mapped to plain text to generate cipher text. The strength of the encryption & Decryption process depends on the strength of sequence generated against crypto analysis.. In this part of work some statistical tests like Uniformity tests, Universal tests & Repetition tests are tried on the sequence generated to test the strength of it.
Holbech, Henrik
Since 2012, European experts work towards the development and validation of an OECD test guideline for mollusc reproductive toxicity with the freshwater gastropod Lymnaea stagnalis. A ring-test involving six laboratories allowed studying reproducibility of results, based on survival and reproduct......Since 2012, European experts work towards the development and validation of an OECD test guideline for mollusc reproductive toxicity with the freshwater gastropod Lymnaea stagnalis. A ring-test involving six laboratories allowed studying reproducibility of results, based on survival...... and reproduction data of snails monitored over 56 days exposure to cadmium. A classical statistical analysis of data was initially conducted by hypothesis tests and fit of parametric concentrationresponse models. However, as mortality occurred in exposed snails, these analyses require to be refined, particularly...... 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...
Gust response analysis and wind tunnel test for a high-aspect ratio wing
Liu Yi; Xie Changchuan; Yang Chao; Cheng Jialin
2016-01-01
A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisci-plinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter bound-ary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quanti-tative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flex-ible wings.
Jet-Surface Interaction Noise from High-Aspect Ratio Nozzles: Test Summary
Brown, Clifford; Podboy, Gary
2017-01-01
Noise and flow data have been acquired for a 16:1 aspect ratio rectangular nozzle exhausting near a simple surface at the NASA Glenn Research Center as part of an ongoing effort to understand, model, and predict the noise produced by current and future concept aircraft employing a tightly integrated engine airframe designs. The particular concept under consideration in this experiment is a blended-wing-body airframe powered by a series of electric fans exhausting through slot nozzle over an aft deck. The exhaust Mach number and surface length were parametrically varied during the test. Far-field noise data were acquired for all nozzle surface geometries and exhaust flow conditions. Phased-array noise source localization data and in-flow pressure data were also acquired for a subset of the isolated (no surface) and surface configurations; these measurements provide data that have proven useful for modeling the jet-surface interaction noise source and the surface effect on the jet-mixing noise in round jets. A summary of the nozzle surface geometry, flow conditions tested, and data collected are presented.
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.
Testing a statistical method of global mean palotemperature estimations in a long climate simulation
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.)
The High $E_T$ Drop of $J/\\psi$ to Drell-Yan Ratio from the Statistical c anti-c Coalescence Model
Kostyuk, A P; Stöcker, H; Greiner, W
2002-01-01
The dependence of the J/psi yield on the transverse energy E_T in heavy ion collisions is considered within the statistical c anti-c coalescence model. The model fits the NA50 data for Pb+Pb collisions at the CERN SPS even in the high-E_T region (E_T > 100 GeV). Here E_T-fluctuations and E_T-losses in the dimuon event sample naturally create the celebrated drop in the J/psi to Drell-Yan ratio.
Statistical analysis of the hen's egg test for micronucleus induction (HET-MN assay).
Hothorn, Ludwig A; Reisinger, Kerstin; Wolf, Thorsten; Poth, Albrecht; Fieblinger, Dagmar; Liebsch, Manfred; Pirow, Ralph
2013-09-18
The HET-MN assay (hen's egg test for micronucleus induction) is different from other in vitro genotoxicity assays in that it includes toxicologically important features such as absorption, distribution, metabolic activation, and excretion of the test compound. As a promising follow-up to complement existing in vitro test batteries for genotoxicity, the HET-MN is currently undergoing a formal validation. To optimize the validation, the present study describes a critical analysis of previously obtained HET-MN data to check the experimental design and to identify the most appropriate statistical procedure to evaluate treatment effects. Six statistical challenges (I-VI) of general relevance were identified, and remedies were provided which can be transferred to similarly designed test methods: a Williams-type trend test is proposed for overdispersed counts (II) by means of a square-root transformation which is robust for small sample sizes (I), variance heterogeneity (III), and possible downturn effects at high doses (IV). Due to near-to-zero or even zero-count data occurring in the negative control (V), a conditional comparison of the treatment groups against the mean of the historical controls (VI) instead of the concurrent control was proposed, which is in accordance with US-FDA recommendations. For the modified Williams-type tests, the power can be estimated depending on the magnitude and shape of the trend, the number of dose groups, and the magnitude of the MN counts in the negative control. The experimental design used previously (i.e. six eggs per dose group, scoring of 1000 cells per egg) was confirmed. The proposed approaches are easily available in the statistical computing environment R, and the corresponding R-codes are provided.
Azim Honarmand; Mohammadreza Safavi; Narges Ansari
2014-01-01
Background: Failed intubation is imperative source of anesthetic interrelated patient′s mortality. The aim of this present study was to compare the ability to predict difficult visualization of the larynx from the following pre-operative airway predictive indices, in isolation and combination: Modified Mallampati test (MMT), the ratio of height to thyromental distance (RHTMD), hyomental distance ratios (HMDR), and the upper-lip-bite test (ULBT). Materials and Methods: We collected data on...
Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses.
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.
Do firms share the same functional form of their growth rate distribution? A new statistical test
Lunardi, Josè T; Lillo, Fabrizio; Mantegna, Rosario N; Gallegati, Mauro
2011-01-01
We introduce a new statistical test of the hypothesis that a balanced panel of firms have the same growth rate distribution or, more generally, that they share the same functional form of growth rate distribution. We applied the test to European Union and US publicly quoted manufacturing firms data, considering functional forms belonging to the Subbotin family of distributions. While our hypotheses are rejected for the vast majority of sets at the sector level, we cannot rejected them at the subsector level, indicating that homogenous panels of firms could be described by a common functional form of growth rate distribution.
Case Studies for the Statistical Design of Experiments Applied to Powered Rotor Wind Tunnel Tests
Overmeyer, Austin D.; Tanner, Philip E.; Martin, Preston B.; Commo, Sean A.
2015-01-01
The application of statistical Design of Experiments (DOE) to helicopter wind tunnel testing was explored during two powered rotor wind tunnel entries during the summers of 2012 and 2013. These tests were performed jointly by the U.S. Army Aviation Development Directorate Joint Research Program Office and NASA Rotary Wing Project Office, currently the Revolutionary Vertical Lift Project, at NASA Langley Research Center located in Hampton, Virginia. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small portion of the overall tests devoted to developing case studies of the DOE approach as it applies to powered rotor testing. A 16-47 times reduction in the number of data points required was estimated by comparing the DOE approach to conventional testing methods. The average error for the DOE surface response model for the OH-58F test was 0.95 percent and 4.06 percent for drag and download, respectively. The DOE surface response model of the Active Flow Control test captured the drag within 4.1 percent of measured data. The operational differences between the two testing approaches are identified, but did not prevent the safe operation of the powered rotor model throughout the DOE test matrices.
Robust Statistical Tests of Dragon-Kings beyond Power Law Distributions
Pisarenko, V F
2011-01-01
We ask the question whether it is possible to diagnose the existence of "Dragon-Kings" (DK), namely anomalous observations compared to a power law background distribution of event sizes. We present two new statistical tests, the U-test and the DK-test, aimed at identifying the existence of even a single anomalous event in the tail of the distribution of just a few tens of observations. The DK-test in particular is derived such that the p-value of its statistic is independent of the exponent characterizing the null hypothesis. We demonstrate how to apply these two tests on the distributions of cities and of agglomerations in a number of countries. We find the following evidence for Dragon-Kings: London in the distribution of city sizes of Great Britain; Moscow and St-Petersburg in the distribution of city sizes in the Russian Federation; and Paris in the distribution of agglomeration sizes in France. True negatives are also reported, for instance the absence of Dragon-Kings in the distribution of cities in Ger...
Application of multiple statistical tests to enhance mass spectrometry-based biomarker discovery
Garner Harold R
2009-05-01
Full Text Available Abstract Background Mass spectrometry-based biomarker discovery has long been hampered by the difficulty in reconciling lists of discriminatory peaks identified by different laboratories for the same diseases studied. We describe a multi-statistical analysis procedure that combines several independent computational methods. This approach capitalizes on the strengths of each to analyze the same high-resolution mass spectral data set to discover consensus differential mass peaks that should be robust biomarkers for distinguishing between disease states. Results The proposed methodology was applied to a pilot narcolepsy study using logistic regression, hierarchical clustering, t-test, and CART. Consensus, differential mass peaks with high predictive power were identified across three of the four statistical platforms. Based on the diagnostic accuracy measures investigated, the performance of the consensus-peak model was a compromise between logistic regression and CART, which produced better models than hierarchical clustering and t-test. However, consensus peaks confer a higher level of confidence in their ability to distinguish between disease states since they do not represent peaks that are a result of biases to a particular statistical algorithm. Instead, they were selected as differential across differing data distribution assumptions, demonstrating their true discriminatory potential. Conclusion The methodology described here is applicable to any high-resolution MALDI mass spectrometry-derived data set with minimal mass drift which is essential for peak-to-peak comparison studies. Four statistical approaches with differing data distribution assumptions were applied to the same raw data set to obtain consensus peaks that were found to be statistically differential between the two groups compared. These consensus peaks demonstrated high diagnostic accuracy when used to form a predictive model as evaluated by receiver operating characteristics
External mechanical work versus oxidative energy consumption ratio during a basketball field test.
Crisafulli, A; Melis, F; Tocco, F; Laconi, P; Lai, C; Concu, A
2002-12-01
A field test consisting of 5 continuous runs at the maximum speed possible, playing the ball, starting from the centre line to the basket with a final shot, was studied in order to obtain an index of mechanical work efficiency in basketball players (micro-index=Jmec/Joxy) and evaluate the correlation between micro-index and velocity, acceleration, mechanical power and lactacid anaerobic capacity, respectively. Eight male basketball players were studied; Jmec was the external mechanical work output obtained by means of a video image analysis software which gave the potential and the kinetic translational energies of athletes running and jumping and their velocity, acceleration and mechanical power. By means of a telemetric device (Kosmed K4), for measuring O2 consumption ( VO2), we obtained oxidative work (Joxy). By using this device we also assessed the excess of CO2, which was considered an index of lactacid anaerobic capacity. Non-parametric Spearman statistics revealed a significant correlation between mu index and mean velocity (ppower (ppower and endurance velocity.
COLOR IMAGE RETRIEVAL BASED ON NON-PARAMETRIC STATISTICAL TESTS OF HYPOTHESIS
R. Shekhar
2016-09-01
Full Text Available A novel method for color image retrieval, based on statistical non-parametric tests such as twosample Wald Test for equality of variance and Man-Whitney U test, is proposed in this paper. The proposed method tests the deviation, i.e. distance in terms of variance between the query and target images; if the images pass the test, then it is proceeded to test the spectrum of energy, i.e. distance between the mean values of the two images; otherwise, the test is dropped. If the query and target images pass the tests then it is inferred that the two images belong to the same class, i.e. both the images are same; otherwise, it is assumed that the images belong to different classes, i.e. both images are different. The proposed method is robust for scaling and rotation, since it adjusts itself and treats either the query image or the target image is the sample of other.
Coulson, Melissa; Healey, Michelle; Fidler, Fiona; Cumming, Geoff
2010-01-01
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, behavioral 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.
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.
An Efficient Frequency Recognition Method Based on Likelihood Ratio Test for SSVEP-Based BCI
Yangsong Zhang
2014-01-01
Full Text Available An efficient frequency recognition method is very important for SSVEP-based BCI systems to improve the information transfer rate (ITR. To address this aspect, for the first time, likelihood ratio test (LRT was utilized to propose a novel multichannel frequency recognition method for SSVEP data. The essence of this new method is to calculate the association between multichannel EEG signals and the reference signals which were constructed according to the stimulus frequency with LRT. For the simulation and real SSVEP data, the proposed method yielded higher recognition accuracy with shorter time window length and was more robust against noise in comparison with the popular canonical correlation analysis- (CCA- based method and the least absolute shrinkage and selection operator- (LASSO- based method. The recognition accuracy and information transfer rate (ITR obtained by the proposed method was higher than those of the CCA-based method and LASSO-based method. The superior results indicate that the LRT method is a promising candidate for reliable frequency recognition in future SSVEP-BCI.
Machado, Armando; Keen, Richard
2002-04-28
This study tested a model of how animals discriminate the relative numerosity of stimuli in successive or sequential presentation tasks. In a discrete-trials procedure, pigeons were shown one light for nf times and then another for nl times. Next they received food for choosing the light that had occurred the least-number of times during the sample. At issue were (a) how performance varies with the interval between the two stimulus sets (the interblock interval) and the interval between the end of the sample and the beginning of the choice period (the retention interval); and (b) whether a simple mathematical model of the discrimination process could account for the data. The model assumed that the influence of a stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent; choice probability is given by the ratio of the influence values of the two stimuli. The model also assumed that as the retention interval elapses there is an increasing probability that the ongoing discriminative process be disrupted and then the animal responds randomly. Results showed that increasing the interblock intervals reduced the probability of choosing the last stimulus of the sample as the least-frequent one. Increasing the retention interval reduced accuracy without inducing any stimulus bias. The model accounted well for the major trends in the data.
Rajesh Singh
2014-11-01
Full Text Available Taguchi statistical design, an orthogonal array (OA method, was used to study the impact of the COD/SO42− ratio, hydraulic retention time (HRT and linoleic acid (LA concentration on sulfate (SO42− reduction in an anaerobic sequencing batch reactor using glucose as the electron donor. Based on the OA, optimum condition for maximum SO42− reduction was evaluated. Increasing the COD/SO42− ratio and HRT caused decreasing SO42− reduction while increased SO42− reduction was observed with increasing LA concentration (1 g L−1. In control (not fed LA cultures, higher SO42− reduction (87% ± 3% was observed at a low COD/SO42− ratio of 0.8. This indicates that increasing SO42− reduction was observed at increasing SO42− loading rates. In general, results from this study reveal that limiting the substrate concentration with high SO42− levels (low COD/SO42− ratio favors high SO42− removal. Surface plots were used to evaluate the significant interactions between the experimental factors. Accuracy of the model was verified using an analysis of residuals. Optimum conditions for maximum SO42− reduction (97.61% were observed at a COD/SO42− ratio of 0.8 (level 1, 12 h HRT (level 1 together with 1000 mg L−1 LA addition (level 3. In general, the Taguchi OA provided a useful approach for predicting the percent SO42− reduction in inhibited mixed anaerobic cultures within the factor levels investigated.
Stefano Caruson
2015-12-01
Full Text Available Abstract The remarkable importance of a calibration of a test lies in the formalization of useful statistical norms. In particular, the determination of these norms is of key importance for the Rorschach Test because of it allows objectifying the estimates of the interpretations’ formal qualities, and help to characterize responses consistent with the common perception. The aim of this work is to communicate the new results provided by a study conducted on Rorschach protocols related to a sample of “non-clinical” subjects. The expert team in Psychodiagnostic of CIFRIC (Italian Center for training, research and clinic in medicine and psychology has carried out the following work identifying the rate at which the details of each card are interpreted by normative sample. The data obtained are systematized in new Location sheets, which refers to the next edition of the "Updated Manual of Locations and Coding of Responses to Rorschach Test". Considering the Rorschach Test one of the more effective means for the acquaintance of the personality, it appears therefore fundamental to provide the professional, who uses it, with the possibility of accessing updated statistical data that reflect the population of reference, in order to deduce from them reliable and objectively valid indications.
A Statistical Approach for Testing Cross-Phenotype Effects of Rare Variants
Broadaway, K. Alaine; Cutler, David J.; Duncan, Richard; Moore, Jacob L.; Ware, Erin B.; Jhun, Min A.; Bielak, Lawrence F.; Zhao, Wei; Smith, Jennifer A.; Peyser, Patricia A.; Kardia, Sharon L.R.; Ghosh, Debashis; Epstein, Michael P.
2016-01-01
Increasing empirical evidence suggests that many genetic variants influence multiple distinct phenotypes. When cross-phenotype effects exist, multivariate association methods that consider pleiotropy are often more powerful than univariate methods that model each phenotype separately. Although several statistical approaches exist for testing cross-phenotype effects for common variants, there is a lack of similar tests for gene-based analysis of rare variants. In order to fill this important gap, we introduce a statistical method for cross-phenotype analysis of rare variants using a nonparametric distance-covariance approach that compares similarity in multivariate phenotypes to similarity in rare-variant genotypes across a gene. The approach can accommodate both binary and continuous phenotypes and further can adjust for covariates. Our approach yields a closed-form test whose significance can be evaluated analytically, thereby improving computational efficiency and permitting application on a genome-wide scale. We use simulated data to demonstrate that our method, which we refer to as the Gene Association with Multiple Traits (GAMuT) test, provides increased power over competing approaches. We also illustrate our approach using exome-chip data from the Genetic Epidemiology Network of Arteriopathy. PMID:26942286
LIU Yan-fang; ZHANG Jian-hua; L Bo; YANG Xiao-hong; LI Yan-gang; WANG Ye; WANG Jiang-min; ZHANG Hui; GUAN Jun-jiao
2013-01-01
Selection of quantitative characteristics, division of their expression ranges, and selection of example varieties are key issues on developing DUS Test Guidelines, which are more crucial for quantitative characteristics since their expressions vary in different degrees. Taking the development of DUS Test Guideline of Ranunculus asiaticus L. as an example, this paper applied statistic-based approaches for the analyses of quantitative characteristics. We selected 9 quantitative characteristics from 18 pre-selected characteristics, based on within-variety uniformity, stability between different growing cycles, and correlation among characteristics, by the analyses of coefficient of variation, paired-samples t-test and partial correlation. The expression ranges of the 9 selected quantitative characteristics were divided into different states using descriptive statistics and distribution frequency of varieties. Eight of the 9 selected quantitative characteristics were categorized as standard characteristics as they showed one peak in distribution frequency of 120 varieties in various expressions of the characteristics, whereas, plant height can be categorized as grouping characteristic since it gave two peaks, and can group the varieties into pot and cut varieties. Finally, box-plot was applied to visually select the example varieties, and varieties 7, 12, and 28 were determined as the example varieties for plant height. The methods described in this paper are effective for the selection of quantitative characteristics, division of expression ranges, and selection of example varieties in Ranunculus asiaticus L. for DUS test, and may also be interest for other plant genera.
Feyissa, Daniel D.; Aher, Yogesh D.; Engidawork, Ephrem; Höger, Harald; Lubec, Gert; Korz, Volker
2017-01-01
Animal models for anxiety, depressive-like and cognitive diseases or aging often involve testing of subjects in behavioral test batteries. The large number of test variables with different mean variations and within and between test correlations often constitute a significant problem in determining essential variables to assess behavioral patterns and their variation in individual animals as well as appropriate statistical treatment. Therefore, we applied a multivariate approach (principal component analysis) to analyse the behavioral data of 162 male adult Sprague-Dawley rats that underwent a behavioral test battery including commonly used tests for spatial learning and memory (holeboard) and different behavioral patterns (open field, elevated plus maze, forced swim test) as well as for motor abilities (Rota rod). The high dimensional behavioral results were reduced to fewer components associated with spatial cognition, general activity, anxiety-, and depression-like behavior and motor ability. The loading scores of individual rats on these different components allow an assessment and the distribution of individual features in a population of animals. The reduced number of components can be used also for statistical calculations like appropriate sample sizes for valid discriminations between experimental groups, which otherwise have to be done on each variable. Because the animals were intact, untreated and experimentally naïve the results reflect trait patterns of behavior and thus individuality. The distribution of animals with high or low levels of anxiety, depressive-like behavior, general activity and cognitive features in a local population provides information of the probability of their appeareance in experimental samples and thus may help to avoid biases. However, such an analysis initially requires a large cohort of animals in order to gain a valid assessment.
Statistical auditing and randomness test of lotto k/N-type games
Coronel-Brizio, H F; Rapallo, Fabio; Scalas, Enrico
2008-01-01
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.
Statistical test of Duane-Hunt's law and its comparison with an alternative law
Perkovac, Milan
2010-01-01
Using Pearson correlation coefficient a statistical analysis of Duane-Hunt and Kulenkampff's measurement results was performed. This analysis reveals that empirically based Duane-Hunt's law is not entirely consistent with the measurement data. The author has theoretically found the action of electromagnetic oscillators, which corresponds to Planck's constant, and also has found an alternative law based on the classical theory. Using the same statistical method, this alternative law is likewise tested, and it is proved that the alternative law is completely in accordance with the measurements. The alternative law gives a relativistic expression for the energy of electromagnetic wave emitted or absorbed by atoms and proves that the empirically derived Planck-Einstein's expression is only valid for relatively low frequencies. Wave equation, which is similar to the Schr\\"odinger equation, and wavelength of the standing electromagnetic wave are also established by the author's analysis. For a relatively low energy...
Statistical auditing and randomness test of lotto k/N-type games
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.
Shah SG
2012-12-01
Full Text Available Syed Ghulam Sarwar Shah,1 Julie Barnett,1 Jasna Kuljis,2 Kate Hone,2 Richard Kaczmarski31Multidisciplinary Assessment of Technology Centre for Healthcare, 2Department of Information Systems and Computing, Brunel University London, Uxbridge, Middlesex, UK; 3Department of Haematology, Hillingdon Hospital, Uxbridge, Middlesex, UKPurpose: To identify factors that determine patients' intentions to use point-of-care medical devices, ie, portable coagulometer devices for self-testing of the international normalized ratio (INR required for ongoing monitoring of blood-coagulation intensity among patients on long-term oral anticoagulation therapy with vitamin K antagonists, eg, warfarin.Methods: A cross-sectional study that applied the technology-acceptance model through a self-completed questionnaire, which was administered to a convenience sample of 125 outpatients attending outpatient anticoagulation services at a district general hospital in London, UK. Data were analyzed using descriptive statistics, factor analyses, and structural equation modeling.Results: The participants were mainly male (64% and aged ≥ 71 years (60%. All these patients were attending the hospital outpatient anticoagulation clinic for INR testing; only two patients were currently using INR self-testing, 84% of patients had no knowledge about INR self-testing using a portable coagulometer device, and 96% of patients were never offered the option of the INR self-testing. A significant structural equation model explaining 79% of the variance in patients’ intentions to use INR self-testing was observed. The significant predictors that directly affected patients' intention to use INR self-testing were the perception of technology (β = 0.92, P < 0.001, trust in doctor (β = −0.24, P = 0.028, and affordability (β = 0.15, P = 0.016. In addition, the perception of technology was significantly affected by trust in doctor (β = 0.43, P = 0.002, age (β = −0.32, P < 0.001, and
Mulcom: a multiple comparison statistical test for microarray data in Bioconductor
Renzulli Tommaso
2011-09-01
Full Text Available Abstract Background Many microarray experiments search for genes with differential expression between a common "reference" group and multiple "test" groups. In such cases currently employed statistical approaches based on t-tests or close derivatives have limited efficacy, mainly because estimation of the standard error is done on only two groups at a time. Alternative approaches based on ANOVA correctly capture within-group variance from all the groups, but then do not confront single test groups with the reference. Ideally, a t-test better suited for this type of data would compare each test group with the reference, but use within-group variance calculated from all the groups. Results We implemented an R-Bioconductor package named Mulcom, with a statistical test derived from the Dunnett's t-test, designed to compare multiple test groups individually against a common reference. Interestingly, the Dunnett's test uses for the denominator of each comparison a within-group standard error aggregated from all the experimental groups. In addition to the basic Dunnett's t value, the package includes an optional minimal fold-change threshold, m. Due to the automated, permutation-based estimation of False Discovery Rate (FDR, the package also permits fast optimization of the test, to obtain the maximum number of significant genes at a given FDR value. When applied to a time-course experiment profiled in parallel on two microarray platforms, and compared with two commonly used tests, Mulcom displayed better concordance of significant genes in the two array platforms (39% vs. 26% or 15%, and higher enrichment in functional annotation to categories related to the biology of the experiment (p value Conclusions The Mulcom package provides a powerful tool for the identification of differentially expressed genes when several experimental conditions are compared against a common reference. The results of the practical example presented here show that lists of
Soil resistivity over root area ratio, soil humidity, and bulk density: laboratory tests
Guastini, Enrico; Giambastiani, Yamuna; Preti, Federico
2015-04-01
Knowledge about root system distribution covers an important role in slope shallow stability stud-ies, as this factor grants an increase in soil geotechnical properties (soil cohesion and friction an-gle) and determines a different underground water circulation. Published studies (Amato et al., 2008 and 2011; Censini et al., 2014) about in situ application of ERT (Electrical Resistivity Tomo-graphy) analysis show how the root presence affects the measurable soil resistivity values, confirm-ing the suitability to investigate the application of such technique, aiming to estimate root density in soil with an indirect and non-invasive method. This study, laboratory-based and led on reconstructed samples in controlled condition, aim to find a correlation between the resistivity variations and the various factors that can affect them (humid-ity, bulk density, presence of foreign bodies, temperature). The tests involved a clay-loam soil (USDA classification) taken from Quaracchi (Florence, Italy), in an experimental fir-wood (Picea abies) owned by the Department of Agricultural, Food and For-estry System, Florence University, a previously chosen site for field ERT applications. The row ma-terial has been dried out in a lab stove, grounded and sieved at 2 mm, and then placed in a lexan box (30 x 20 x 20 cm) without compaction. Inside the sample have been inserted 3 series of 4 iron electrodes, insulated along the shaft and with the conductive end placed at three different depth: 2 cm from surface, in the middle of the sample and in contact with the bottom of the box; resistivity measures are conducted on the three levels using a Syscal R2 with electrodes connected in a dipole-dipole configuration. Root presence is simulated inserting bamboo spits (simple geometry, replicable "R.A.R.") in varying number from 0 to 16 in every area between two contiguous electrodes. The tests are repeated in time, monitoring the natural variations in humidity (evapotranspiration) and bulk
SNSequate: Standard and Nonstandard Statistical Models and Methods for Test Equating
Jorge González
2014-09-01
Full Text Available Equating is a family of statistical models and methods that are used to adjust scores on two or more versions of a test, so that the scores from different tests may be used interchangeably. In this paper we present the R package SNSequate which implements both standard and nonstandard statistical models and methods for test equating. The package construction was motivated by the need of having a modular, simple, yet comprehensive, and general software that carries out traditional and new equating methods. SNSequate currently implements the traditional mean, linear and equipercentile equating methods, as well as the mean-mean, mean-sigma, Haebara and Stocking-Lord item response theory linking methods. It also supports the newest methods such as local equating, kernel equating, and item response theory parameter linking methods based on asymmetric item characteristic functions. Practical examples are given to illustrate the capabilities of the software. A list of other programs for equating is presented, highlighting the main differences between them. Future directions for the package are also discussed.
Chu, Tsong-Lun [Brookhaven National Lab. (BNL), Upton, NY (United States); Varuttamaseni, Athi [Brookhaven National Lab. (BNL), Upton, NY (United States); Baek, Joo-Seok [Brookhaven National Lab. (BNL), Upton, NY (United States)
2016-11-01
The U.S. Nuclear Regulatory Commission (NRC) encourages the use of probabilistic risk assessment (PRA) technology in all regulatory matters, to the extent supported by the state-of-the-art in PRA methods and data. Although much has been accomplished in the area of risk-informed regulation, risk assessment for digital systems has not been fully developed. The NRC established a plan for research on digital systems to identify and develop methods, analytical tools, and regulatory guidance for (1) including models of digital systems in the PRAs of nuclear power plants (NPPs), and (2) incorporating digital systems in the NRC's risk-informed licensing and oversight activities. Under NRC's sponsorship, Brookhaven National Laboratory (BNL) explored approaches for addressing the failures of digital instrumentation and control (I and C) systems in the current NPP PRA framework. Specific areas investigated included PRA modeling digital hardware, development of a philosophical basis for defining software failure, and identification of desirable attributes of quantitative software reliability methods. Based on the earlier research, statistical testing is considered a promising method for quantifying software reliability. This paper describes a statistical software testing approach for quantifying software reliability and applies it to the loop-operating control system (LOCS) of an experimental loop of the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL).
Amylase-creatinine clearance ratio. A simple test to predict gentamicin nephrotoxicity.
Aderka, D; Tene, M; Graff, E; Levo, Y
1988-05-01
The initial target of aminoglycoside nephrotoxicity is the proximal tubule. Yet, no simple test is available to predict such toxicity. Taking advantage of the fact that amylase is filtered in the glomerulus and reabsorbed by the proximal tubules, we prospectively examined in 23 patients if changes in renal amylase creatinine clearance ratio (ACCR) can predict gentamicin nephrotoxicity. Eighteen of these patients had an initial creatinine clearance (rCcr) above 30 mL/min. Eleven of them (group A) had an ACCR above 3.5% (control 3% +/- 1.03%) and all exhibited an average reduction of 32.2% +/- 11.6% in rCcr following one week of gentamicin therapy. In contrast, only one of seven patients (group B) with an initial ACCR below 3.5% had a reduction, albeit transient, in rCcr. During gentamicin therapy, group A patients had a further increase in ACCR which was proportional to the reduction observed in rCcr (r = -.54). Our preliminary data suggest that ACCR may prove a simple and possibly a reliable predictor of kidney function deterioration during gentamicin therapy in patients with rCcr above 30 mL/min: patients with pretherapy ACCR above 3.5% may exhibit a deterioration in the creatinine clearance during the first week of therapy. For patients with pretherapy renal failure (rCcr less than 30 mL/min) the creatinine levels (but not the ACCR) seem to retain their significance in predicting and monitoring further renal function deterioration during aminoglycoside therapy.
Wapnick, S; Evans, M I; Hadas, N; Grosberg, S J
1980-05-01
The mean +/- S.E.M. ratio of amylase to creatinine clearance significantly increased at 24 hours after operations on the stomach and gallbladder but not after operations at sites remote from the abdominal cavity. Clinically, the elevated amylase to creatinine clearance ratio was not accompanied by pancreatitis. In dogs, surgical handling of the pancreas alone caused a significant increase in this measurement. The amylase to creatinine clearance ratio is not likely to be helpful in predicting the rare, but serious, postoperative complication of pancreatitis.
Statistical Testing of Dynamically Downscaled Rainfall Data for the East Coast of Australia
Parana Manage, Nadeeka; Lockart, Natalie; Willgoose, Garry; Kuczera, George
2015-04-01
This study performs a validation of statistical properties of downscaled climate data, concentrating on the rainfall which is required for hydrology predictions used in reservoir simulations. The data sets used in this study have been produced by the NARCliM (NSW/ACT Regional Climate Modelling) project which provides a dynamically downscaled climate dataset for South-East Australia at 10km resolution. NARCliM has used three configurations of the Weather Research Forecasting Regional Climate Model and four different GCMs (MIROC-medres 3.2, ECHAM5, CCCMA 3.1 and CSIRO mk3.0) from CMIP3 to perform twelve ensembles of simulations for current and future climates. Additionally to the GCM-driven simulations, three control run simulations driven by the NCEP/NCAR reanalysis for the entire period of 1950-2009 has also been performed by the project. The validation has been performed in the Upper Hunter region of Australia which is a semi-arid to arid region 200 kilometres North-West of Sydney. The analysis used the time series of downscaled rainfall data and ground based measurements for selected Bureau of Meteorology rainfall stations within the study area. The initial testing of the gridded rainfall was focused on the autoregressive characteristics of time series because the reservoir performance depends on long-term average runoffs. A correlation analysis was performed for fortnightly, monthly and annual averaged time resolutions showing a good statistical match between reanalysis and ground truth. The spatial variation of the statistics of gridded rainfall series were calculated and plotted at the catchment scale. The spatial correlation analysis shows a poor agreement between NARCliM data and ground truth at each time resolution. However, the spatial variability plots show a strong link between the statistics and orography at the catchment scale.
Sassenhagen, Jona; Alday, Phillip M
2016-11-01
Experimental research on behavior and cognition frequently rests on stimulus or subject selection where not all characteristics can be fully controlled, even when attempting strict matching. For example, when contrasting patients to controls, variables such as intelligence or socioeconomic status are often correlated with patient status. Similarly, when presenting word stimuli, variables such as word frequency are often correlated with primary variables of interest. One procedure very commonly employed to control for such nuisance effects is conducting inferential tests on confounding stimulus or subject characteristics. For example, if word length is not significantly different for two stimulus sets, they are considered as matched for word length. Such a test has high error rates and is conceptually misguided. It reflects a common misunderstanding of statistical tests: interpreting significance not to refer to inference about a particular population parameter, but about 1. the sample in question, 2. the practical relevance of a sample difference (so that a nonsignificant test is taken to indicate evidence for the absence of relevant differences). We show inferential testing for assessing nuisance effects to be inappropriate both pragmatically and philosophically, present a survey showing its high prevalence, and briefly discuss an alternative in the form of regression including nuisance variables.
Escott-Price, Valentina; Ghodsi, Mansoureh; Schmidt, Karl Michael
2014-04-01
We evaluate the effect of genotyping errors on the type-I error of a general association test based on genotypes, showing that, in the presence of errors in the case and control samples, the test statistic asymptotically follows a scaled non-central $\\chi ^2$ distribution. We give explicit formulae for the scaling factor and non-centrality parameter for the symmetric allele-based genotyping error model and for additive and recessive disease models. They show how genotyping errors can lead to a significantly higher false-positive rate, growing with sample size, compared with the nominal significance levels. The strength of this effect depends very strongly on the population distribution of the genotype, with a pronounced effect in the case of rare alleles, and a great robustness against error in the case of large minor allele frequency. We also show how these results can be used to correct $p$-values.
Mekik, Figen; Loubere, Paul; Richaud, Mathieu
2007-03-01
The organic carbon to calcite flux ratio (rain ratio) has a profound effect on the preservation of carbonates in the deep sea and may influence atmospheric pCO 2 over millennia. Unfortunately, the degree to which the rain ratio varies in the more productive regions of the oceans is not well determined with sediment trap data. The rain ratio in the upper ocean appears dominantly linked to diatom productivity, which is not necessarily directly linked to total production and may be regionally variable. However, ballasting and protection of organic carbon by calcareous particles in the deeps may limit ratio variability at the seafloor. Sediment trap data do not exist for the regional determination of rain ratios in key highly productive areas like the eastern equatorial Pacific (EEP). To overcome this, we turn to surface sediment composition and accumulation rates as a representation of modern ratio variation. We present 230Thorium ( 230Th)-normalized carbonate, opal, organic carbon and detrital matter accumulation rates from core top samples in the EEP. We demonstrate a novel approach for estimating modern rain ratios from sedimentary proxies by (1) calculating vertical calcite flux from 230Th-normalized carbonate accumulation rates (CARs) with correction for preservation and (2) calculating organic carbon fluxes with multiple algorithms that depend in varying degrees on ballasting. We find that organic carbon flux estimates from algorithms with and without a ballasting function produce results different from one another. Sediment accumulation rates for opal reflect the likely pattern of diatom production. By contrast, the organic carbon accumulation rate does not correlate well with surface ocean productivity or any of our algorithm-based organic carbon flux estimates. Instead, it correlates with the detrital component of the sediments suggesting an allochthonous input to sedimentary organic carbon accumulation in the EEP, which reduces its value as a productivity
Recent developments in the use of isotope ratio mass spectrometry in sports drug testing.
Piper, Thomas; Emery, Caroline; Saugy, Martial
2011-08-01
According to the annual report of the World Anti-Doping Agency, steroids are the most frequently detected class of doping agents. Detecting the misuse of endogenously occurring steroids, i.e. steroids such as testosterone that are produced naturally by humans, is one of the most challenging issues in doping control analysis. The established thresholds for urinary concentrations or concentration ratios such as the testosterone/epitestosterone quotient are sometimes inconclusive owing to the large biological variation in these parameters.For more than 15 years, doping control laboratories focused on the carbon isotope ratios of endogenous steroids to distinguish between naturally elevated steroid profile parameters and illicit administration of steroids. A variety of different methods has been developed throughout the last decade and the number of different steroids under investigation by isotope ratio mass spectrometry has recently grown considerably. Besides norandrosterone, boldenone was found to occur endogenously in rare cases and the misuse of corticosteroids or epitestosterone can now be detected with the aid of carbon isotope ratios as well. In addition, steroids excreted as sulfoconjugates were investigated, and the first results regarding hydrogen isotope ratios recently became available.All of these will be presented in detail within this review together with some considerations on validation issues and on identification of parameters influencing steroidal isotope ratios in urine.
Observations in the statistical analysis of NBG-18 nuclear graphite strength tests
Hindley, Michael P.; Mitchell, Mark N.; Blaine, Deborah C.; Groenwold, Albert A.
2012-01-01
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.
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.
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.
Real space tests of the statistical isotropy and Gaussianity of the three year WMAP data
Lew, Bartosz
2008-01-01
CONTEXT: Gaussianity will become a strong observational tool allowing to constrain viable inflationary models. AIMS: In this paper, we introduce and analyze a new method for testing SI and Gaussianity and apply it to the 3 years WMAP CMB data. METHODS: We use an original pixelization scheme to divide the sky into regions of varying size and shape. We then measure the first four moments of the one-point distribution within these regions and using their simulated spatial distributions we test the statistical isotropy and Gaussianity hypotheses. By randomly varying orientations of these regions, their angular size and shape, we sample the underlying CMB field in a new manner, that offers a richer exploration of data the content. In our analysis we account for all correlations between different regions and also show the impact on the results when these correlations are neglected. The statistical significance is assessed via comparison with realistic Monte-Carlo simulations of the observed data. RESULTS: We find t...
Bozak, Richard F.
2017-01-01
In February 2017, aerodynamic and acoustic testing was completed on a scale-model high bypass ratio turbofan rotor, R4, in an internal flow component test facility. The objective of testing was to determine the aerodynamic and acoustic impact of fan casing treatments designed to reduce noise. The baseline configuration consisted of the R4 rotor with a hardwall fan case. Data are presented for a baseline acoustic run with fan exit instrumentation removed to give a clean acoustic configuration.
Minty, Ross; Thomason, James L.; Petersen, Helga Nørgaard
2015-01-01
This paper focuses on an investigation into the role of the epoxy resin: curing agent ratio in composite interfacial shear strength of glass fibre composites. The procedure involved changing the percentage of curing agent (Triethylenetetramine [TETA]) used in the mixture with several different...... percentages used, ranging from 4% up to 30%, including the stoichiometric ratio. It was found by using the microbond test, that there may exist a relationship between the epoxy resin to curing agent ratio and the level of adhesion between the reinforcing fibre and the polymer matrix of the composite....
Statistical analysis and conformity testing of concrete in port construction work
M. C. Larrossa
Full Text Available Conformity control of concrete is part of a range of control and standard methods which must be employed in all construction work to assure its compliance with quality requirements. The compressive strength of the concrete is considered as a random variable that must be controlled by standardized sampling and testing in order to ensure the structural safety. Therefore, the use of a large amount of compressive strength test results of concretes with similar characteristics has been seen as an important tool in the assessment of current standard norms. This paper describes an analysis based on the conformity control used in large port construction works which have recently been carried out in the Rio Grande Port, located in Rio Grande, RS, Brazil. Statistical analyses were performed and acceptance tests of the product were conducted. They were based on the acceptance criteria of different methodologies from different continents and showed the variations that can occur in the results of the conformity testing, depending on the adopted model. It is worth mentioning that the concrete used in port construction works in the region has been in accordance with current Brazilian norms.
Debate on GMOs health risks after statistical findings in regulatory tests.
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.
Debate on GMOs Health Risks after Statistical Findings in Regulatory Tests
Joël Spiroux de Vendômois, Dominique Cellier, Christian Vélot, Emilie Clair, Robin Mesnage, Gilles-Eric Séralini
2010-01-01
Full Text Available 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.
Apostolos, Batsidis; Leandro, Pardo; Konstantinos, Zografos
2011-01-01
Recently Batsidis et al. (2011) have presented a new procedure based on divergence measures for testing the hypothesis of the existence of a change point in exponential populations. A simulation study was carried out using the asymptotic critical points obtained from the asymptotic distribution of the new test statistics introduced. The main purpose of this paper is to use the behavior of the test statistics introduced in the cited paper of Batsidis et al. (2011) using simulated critical points.
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).
Testing of January Anomaly at ISE-100 Index with Power Ratio Method
Şule Yüksel Yiğiter
2015-12-01
Full Text Available AbstractNone of investors that can access all informations in the same ratio is not possible to earn higher returns according to Efficient Market Hypothesis. However, it has been set forth effect of time on returns in several studies and reached conflicting conclusions with hypothesis. In this context, one of the most important existing anomalies is also January month anomaly. In this study, it has been researched that if there is January effect in BIST-100 index covering 2008-2014 period by using power ratio method. The presence of January month anomaly in BIST-100 index within specified period determined by analysis results.Keywords: Efficient Markets Hypothesis, January Month Anomaly, Power Ratio MethodJEL Classification Codes: G1,C22
Testing for Near I(2) Trends When the Signal-to-Noise Ratio Is Small
Juselius, Katarina
2014-01-01
Researchers seldom find evidence of I(2) in exchange rates, prices, and other macroeconomics time series when they test the order of integration using univariate Dickey-Fuller tests. In contrast, when using the multivariate ML trace test we frequently find double unit roots in the data. Our paper...
Statistics 101 for Radiologists.
Anvari, Arash; Halpern, Elkan F; Samir, Anthony E
2015-10-01
Diagnostic tests have wide clinical applications, including screening, diagnosis, measuring treatment effect, and determining prognosis. Interpreting diagnostic test results requires an understanding of key statistical concepts used to evaluate test efficacy. This review explains descriptive statistics and discusses probability, including mutually exclusive and independent events and conditional probability. In the inferential statistics section, a statistical perspective on study design is provided, together with an explanation of how to select appropriate statistical tests. Key concepts in recruiting study samples are discussed, including representativeness and random sampling. Variable types are defined, including predictor, outcome, and covariate variables, and the relationship of these variables to one another. In the hypothesis testing section, we explain how to determine if observed differences between groups are likely to be due to chance. We explain type I and II errors, statistical significance, and study power, followed by an explanation of effect sizes and how confidence intervals can be used to generalize observed effect sizes to the larger population. Statistical tests are explained in four categories: t tests and analysis of variance, proportion analysis tests, nonparametric tests, and regression techniques. We discuss sensitivity, specificity, accuracy, receiver operating characteristic analysis, and likelihood ratios. Measures of reliability and agreement, including κ statistics, intraclass correlation coefficients, and Bland-Altman graphs and analysis, are introduced.
A statistical design for testing transgenerational genomic imprinting in natural human populations.
Yao Li
Full Text Available Genomic imprinting is a phenomenon in which the same allele is expressed differently, depending on its parental origin. Such a phenomenon, also called the parent-of-origin effect, has been recognized to play a pivotal role in embryological development and pathogenesis in many species. Here we propose a statistical design for detecting imprinted loci that control quantitative traits based on a random set of three-generation families from a natural population in humans. This design provides a pathway for characterizing the effects of imprinted genes on a complex trait or disease at different generations and testing transgenerational changes of imprinted effects. The design is integrated with population and cytogenetic principles of gene segregation and transmission from a previous generation to next. The implementation of the EM algorithm within the design framework leads to the estimation of genetic parameters that define imprinted effects. A simulation study is used to investigate the statistical properties of the model and validate its utilization. This new design, coupled with increasingly used genome-wide association studies, should have an immediate implication for studying the genetic architecture of complex traits in humans.
A statistical design for testing transgenerational genomic imprinting in natural human populations.
Li, Yao; Guo, Yunqian; Wang, Jianxin; Hou, Wei; Chang, Myron N; Liao, Duanping; Wu, Rongling
2011-02-25
Genomic imprinting is a phenomenon in which the same allele is expressed differently, depending on its parental origin. Such a phenomenon, also called the parent-of-origin effect, has been recognized to play a pivotal role in embryological development and pathogenesis in many species. Here we propose a statistical design for detecting imprinted loci that control quantitative traits based on a random set of three-generation families from a natural population in humans. This design provides a pathway for characterizing the effects of imprinted genes on a complex trait or disease at different generations and testing transgenerational changes of imprinted effects. The design is integrated with population and cytogenetic principles of gene segregation and transmission from a previous generation to next. The implementation of the EM algorithm within the design framework leads to the estimation of genetic parameters that define imprinted effects. A simulation study is used to investigate the statistical properties of the model and validate its utilization. This new design, coupled with increasingly used genome-wide association studies, should have an immediate implication for studying the genetic architecture of complex traits in humans.
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.
Tropospheric delay statistics measured by two site test interferometers at Goldstone, California
Morabito, David D.; D'Addario, Larry R.; Acosta, Roberto J.; Nessel, James A.
2013-12-01
Site test interferometers (STIs) have been deployed at two locations within the NASA Deep Space Network tracking complex in Goldstone, California. An STI measures the difference of atmospheric delay fluctuations over a distance comparable to the separations of microwave antennas that could be combined as phased arrays for communication and navigation. The purpose of the Goldstone STIs is to assess the suitability of Goldstone as an uplink array site and to statistically characterize atmosphere-induced phase delay fluctuations for application to future arrays. Each instrument consists of two ~1 m diameter antennas and associated electronics separated by ~200 m. The antennas continuously observe signals emitted by geostationary satellites and produce measurements of the phase difference between the received signals. The two locations at Goldstone are separated by 12.5 km and differ in elevation by 119 m. We find that their delay fluctuations are statistically similar but do not appear as shifted versions of each other, suggesting that the length scale for evolution of the turbulence pattern is shorter than the separation between instruments. We also find that the fluctuations are slightly weaker at the higher altitude site.
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.
Statistical Degradation Models for Reliability Analysis in Non-Destructive Testing
Chetvertakova, E. S.; Chimitova, E. V.
2017-04-01
In this paper, we consider the application of the statistical degradation models for reliability analysis in non-destructive testing. Such models enable to estimate the reliability function (the dependence of non-failure probability on time) for the fixed critical level using the information of the degradation paths of tested items. The most widely used models are the gamma and Wiener degradation models, in which the gamma or normal distributions are assumed as the distribution of degradation increments, respectively. Using the computer simulation technique, we have analysed the accuracy of the reliability estimates, obtained for considered models. The number of increments can be enlarged by increasing the sample size (the number of tested items) or by increasing the frequency of measuring degradation. It has been shown, that the sample size has a greater influence on the accuracy of the reliability estimates in comparison with the measuring frequency. Moreover, it has been shown that another important factor, influencing the accuracy of reliability estimation, is the duration of observing degradation process.
2008-01-01
Pattern informatics (PI) model is one of the recently developed predictive models of earthquake phys- ics based on the statistical mechanics of complex systems. In this paper, retrospective forecast test of the PI model was conducted for the earthquakes in Sichuan-Yunnan region since 1988, exploring the possibility to apply this model to the estimation of time-dependent seismic hazard in continental China. Regional earthquake catalogue down to ML3.0 from 1970 to 2007 was used. The ‘target magnitude’ for the forecast test was MS5.5. Fifteen-year long ‘sliding time window’ was used in the PI calculation, with ‘anomaly training time window’ being 5 years and ‘forecast time window’ being 5 years, respectively. Receiver operating characteristic (ROC) test was conducted for the evaluation of the forecast result, showing that the PI forecast outperforms not only random guess but also the simple number counting approach based on the clustering hypothesis of earthquakes (the RI forecast). If the ‘forecast time window’ was shortened to 3 years and 1 year, respectively, the forecast capability of the PI model de- creased significantly, albeit outperformed random forecast. For the one year ‘forecast time window’, the PI result was almost comparable to the RI result, indicating that clustering properties play a more important role at this time scale.
Ma, Cong
2016-01-01
We use cosmological luminosity distance ($d_L$) from the JLA Type Ia supernovae compilation and angular-diameter distance ($d_A$) based on BOSS and WiggleZ baryon acoustic oscillation measurements to test the distance-duality relation $\\eta \\equiv d_L / [ (1 + z)^2 d_A ] = 1$. The $d_L$ measurements are matched to $d_A$ redshift by a statistically-motivated compression procedure. By means of Monte Carlo methods, non-trivial and correlated distributions of $\\eta$ can be explored in a straightforward manner without resorting to a particular evolution template $\\eta(z)$. Assuming Planck cosmological parameter uncertainty, we find 5% constraints in favor of $\\eta = 1$, consistent with the weaker 7--10% constraints obtained using WiggleZ data. These results stand in contrast to previous claims that $\\eta < 1$ has been found close to or above $1\\sigma$ level.
Statistical Testing of Segment Homogeneity in Classification of Piecewise–Regular Objects
Savchenko Andrey V.
2015-12-01
Full Text Available The paper is focused on the problem of multi-class classification of composite (piecewise-regular objects (e.g., speech signals, complex images, etc.. We propose a mathematical model of composite object representation as a sequence of independent segments. Each segment is represented as a random sample of independent identically distributed feature vectors. Based on this model and a statistical approach, we reduce the task to a problem of composite hypothesis testing of segment homogeneity. Several nearest-neighbor criteria are implemented, and for some of them the well-known special cases (e.g., the Kullback–Leibler minimum information discrimination principle, the probabilistic neural network are highlighted. It is experimentally shown that the proposed approach improves the accuracy when compared with contemporary classifiers.
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 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.
Comparison of statistical models to estimate daily milk yield in single milking testing schemes
Marija Klopcˇic
2010-01-01
Full Text Available Different statistical models were compared to estimate daily milk yield from morning or evening milking test results. The experiment was conducted on 14 family farms with 325 recorded cows. The amount of explained variance was higher for models including the effects of partial milk yield, the interval between successive milking, the interaction between partial milk yield and the milking interval and the farm (R2 = 0.976 for AM, R2 = 0.956 for PM than for models including partial milk yield effect only (R2 = 0.957 for AM, R2 = 0.937 for PM. Estimates of daily milk yield from linear models were more accurate than those obtained by doubling single milking weights. The results show that more complex model gives the best fit to the data. Differences between models according to determination and correlation coefficient were minor. Further investigations on larger sets of data are needed to draw more general conclusion.
Experimental Test of Heisenberg's Measurement Uncertainty Relation Based on Statistical Distances
Ma, Wenchao; Ma, Zhihao; Wang, Hengyan; Chen, Zhihua; Liu, Ying; Kong, Fei; Li, Zhaokai; Peng, Xinhua; Shi, Mingjun; Shi, Fazhan; Fei, Shao-Ming; Du, Jiangfeng
2016-04-01
Incompatible observables can be approximated by compatible observables in joint measurement or measured sequentially, with constrained accuracy as implied by Heisenberg's original formulation of the uncertainty principle. Recently, Busch, Lahti, and Werner proposed inaccuracy trade-off relations based on statistical distances between probability distributions of measurement outcomes [P. Busch et al., Phys. Rev. Lett. 111, 160405 (2013); P. Busch et al., Phys. Rev. A 89, 012129 (2014)]. Here we reformulate their theoretical framework, derive an improved relation for qubit measurement, and perform an experimental test on a spin system. The relation reveals that the worst-case inaccuracy is tightly bounded from below by the incompatibility of target observables, and is verified by the experiment employing joint measurement in which two compatible observables designed to approximate two incompatible observables on one qubit are measured simultaneously.
A Statistical Framework for Testing the Causal Effects of Fetal Drive
Nianjun eLiu
2015-01-01
Full Text Available Maternal genetic and phenotypic characteristics (e.g., metabolic and behavioral affect both the intrauterine milieu and lifelong health trajectories of their fetuses. Yet at the same time, fetal genotype may affect processes that alter pre and postnatal maternal physiology, and the subsequent health of both fetus and mother. We refer to these latter effects as ‘fetal drive.’ If fetal genotype is driving physiologic, metabolic, and behavioral phenotypic changes in the mother, there is a possibility of differential effects with different fetal genomes inducing different long-term effects on both maternal and fetal health, mediated through intrauterine environment. This proposed mechanistic path remains largely unexamined and untested. In this study, we offer a statistical method to rigorously test this hypothesis and make causal inferences in humans by relying on the (conditional randomization inherent in the process of meiosis. For illustration, we apply this method to a dataset from the Framingham Heart Study.
Colegrave, Nick; Ruxton, Graeme D
2017-03-29
A common approach to the analysis of experimental data across much of the biological sciences is test-qualified pooling. Here non-significant terms are dropped from a statistical model, effectively pooling the variation associated with each removed term with the error term used to test hypotheses (or estimate effect sizes). This pooling is only carried out if statistical testing on the basis of applying that data to a previous more complicated model provides motivation for this model simplification; hence the pooling is test-qualified. In pooling, the researcher increases the degrees of freedom of the error term with the aim of increasing statistical power to test their hypotheses of interest. Despite this approach being widely adopted and explicitly recommended by some of the most widely cited statistical textbooks aimed at biologists, here we argue that (except in highly specialized circumstances that we can identify) the hoped-for improvement in statistical power will be small or non-existent, and there is likely to be much reduced reliability of the statistical procedures through deviation of type I error rates from nominal levels. We thus call for greatly reduced use of test-qualified pooling across experimental biology, more careful justification of any use that continues, and a different philosophy for initial selection of statistical models in the light of this change in procedure.
Surrogate/spent fuel sabotage aerosol ratio testing:phase 1 summary and results.
Vigil, Manuel Gilbert; Sorenson, Ken Bryce; Lange, F. (Gesellschaft fur Anlagen- und reaktorsicherheit (GRS), Germany); Nolte, O. (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Koch, W. (Fraunhofer Institut fur Toxikologie und Experimentelle Medizin, Germany); Dickey, Roy R.; Yoshimura, Richard Hiroyuki; Molecke, Martin Alan; Autrusson, Bruno (Institut de Radioprotection et de Surete Nucleaire (IRSN), France); Young, F. I. (U.S. Nuclear Regulatory Commission); Pretzsch, Gunter Guido (Gesellschaft fur Anlagen- und reaktorsicherheit (GRS), Germany)
2005-10-01
This multinational test program is quantifying the aerosol particulates produced when a high energy density device (HEDD) impacts surrogate material and actual spent fuel test rodlets. The experimental work, performed in four consecutive test phases, has been in progress for several years. The overall program provides needed data that are relevant to some sabotage scenarios in relation to spent fuel transport and storage casks, and associated risk assessments. This program also provides significant political benefits in international cooperation for nuclear security related evaluations. The spent fuel sabotage--aerosol test program is coordinated with the international Working Group for Sabotage Concerns of Transport and Storage Casks (WGSTSC), and supported by both the U.S. Department of Energy and Nuclear Regulatory Commission. This report summarizes the preliminary, Phase 1 work performed in 2001 and 2002 at Sandia National Laboratories and the Fraunhofer Institute, Germany, and documents the experimental results obtained, observations, and preliminary interpretations. Phase 1 testing included: performance quantifications of the HEDD devices; characterization of the HEDD or conical shaped charge (CSC) jet properties with multiple tests; refinement of the aerosol particle collection apparatus being used; and, CSC jet-aerosol tests using leaded glass plates and glass pellets, serving as representative brittle materials. Phase 1 testing was quite important for the design and performance of the following Phase 2 test program and test apparatus.
Almuallim, H. [King Fahd Univ. of Petroleum & Minerals, Dhahran (Saudi Arabia); Akiba, Yasuhiro; Kaneda, Shigeo [NTT Communication Science Labs., Kanagawa (Japan)
1996-12-31
Given a set of training examples S and a tree-structured attribute x, the goal in this work is to find a multiple-split test defined on x that maximizes Quinlan`s gain-ratio measure. The number of possible such multiple-split tests grows exponentially in the size of the hierarchy associated with the attribute. It is, therefore, impractical to enumerate and evaluate all these tests in order to choose the best one. We introduce an efficient algorithm for solving this problem that guarantees maximizing the gain-ratio over all possible tests. For a training set of m examples and an attribute hierarchy of height d, our algorithm runs in time proportional to dm, which makes it efficient enough for practical use.
Pratibha Jain Shah; Kamta Prasad Dubey; Jai Prakash Yadav
2013-01-01
Background: Various anatomical measurements and non-invasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Recently introduced "Upper lip bite test" (ULBT) and "Ratio of height to Thyromental distance" (RHTMD) are claimed to have high predictability. We conducted a study to compare the Predictive Value of ULBT and RHTMD with Mouth opening (Inter-Incisor gap) (IIG), Modified Mallampatti Test (MMT), Head and neck movement (HNM) and Thyroment...
Martyna, Agnieszka; Zadora, Grzegorz; Stanimirova, Ivana; Ramos, Daniel
2014-05-01
The aim of the study was to investigate the applicability of the likelihood ratio (LR) approach for verifying the authenticity of 178 samples of 3 Italian wine brands: Barolo, Barbera, and Grignolino described by 27 parameters describing their chemical compositions. Since the problem of products authenticity may be of forensic interest, the likelihood ratio approach, expressing the role of the forensic expert, was proposed for determining the true origin of wines. It allows us to analyse the evidence in the context of two hypotheses, that the object belongs to one or another wine brand. Various LR models were the subject of the research and their accuracy was evaluated by the Empirical cross entropy (ECE) approach. The rates of correct classifications for the proposed models were higher than 90% and their performance evaluated by ECE was satisfactory.
THE GAS/DUST RATIO OF CIRCUMSTELLAR DISKS: TESTING MODELS OF PLANETESIMAL FORMATION
Horne, David [New York Center for Astrobiology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180-3590 (United States); Gibb, Erika [Department of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121 (United States); Rettig, Terrence W.; Tilley, David; Balsara, Dinshaw [Center for Astrophysics, University of Notre Dame, Notre Dame, IN 46556 (United States); Brittain, Sean [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)
2012-07-20
We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. {sup 12}CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig et al.
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…
Perschel, F.H.; Schemer, R.; Seiler, L.; Reincke, M.; Deinum, J.; Maser-Gluth, C.; Mechelhoff, D.; Tauber, R.; Diederich, S.
2004-01-01
BACKGROUND: The ratio of plasma aldosterone concentration to plasma renin activity (PAC/PRA) is the most common screening test for primary hyperaldosteronism (PHA), but it is not standardized among laboratories. We evaluated new automated assays for the simultaneous measurement of PAC and plasma ren
Statistical methods for the analysis of a screening test for chronic beryllium disease
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.
Statistical testing of the full-range leadership theory in nursing.
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.
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 hypothes
Can persistence hunting signal male quality? A test considering digit ratio in endurance athletes.
Daniel Longman
Full Text Available Various theories have been posed to explain the fitness payoffs of hunting success among hunter-gatherers. 'Having' theories refer to the acquisition of resources, and include the direct provisioning hypothesis. In contrast, 'getting' theories concern the signalling of male resourcefulness and other desirable traits, such as athleticism and intelligence, via hunting prowess. We investigated the association between androgenisation and endurance running ability as a potential signalling mechanism, whereby running prowess, vital for persistence hunting, might be used as a reliable signal of male reproductive fitness by females. Digit ratio (2D:4D was used as a proxy for prenatal androgenisation in 439 males and 103 females, while a half marathon race (21km, representing a distance/duration comparable with that of persistence hunting, was used to assess running ability. Digit ratio was significantly and positively correlated with half-marathon time in males (right hand: r = 0.45, p<0.001; left hand: r = 0.42, p<0.001 and females (right hand: r = 0.26, p<0.01; left hand: r = 0.23, p = 0.02. Sex-interaction analysis showed that this correlation was significantly stronger in males than females, suggesting that androgenisation may have experienced stronger selective pressure from endurance running in males. As digit ratio has previously been shown to predict reproductive success, our results are consistent with the hypothesis that endurance running ability may signal reproductive potential in males, through its association with prenatal androgen exposure. However, further work is required to establish whether and how females respond to this signalling for fitness.
Flynn, Clare; Pickering, Kenneth E.; Crawford, James H.; Lamsol, Lok; Krotkov, Nickolay; Herman, Jay; Weinheimer, Andrew; Chen, Gao; Liu, Xiong; Szykman, James;
2014-01-01
To investigate the ability of column (or partial column) information to represent surface air quality, results of linear regression analyses between surface mixing ratio data and column abundances for O3 and NO2 are presented for the July 2011 Maryland deployment of the DISCOVER-AQ mission. Data collected by the P-3B aircraft, ground-based Pandora spectrometers, Aura/OMI satellite instrument, and simulations for July 2011 from the CMAQ air quality model during this deployment provide a large and varied data set, allowing this problem to be approached from multiple perspectives. O3 columns typically exhibited a statistically significant and high degree of correlation with surface data (R(sup 2) > 0.64) in the P- 3B data set, a moderate degree of correlation (0.16 < R(sup 2) < 0.64) in the CMAQ data set, and a low degree of correlation (R(sup 2) < 0.16) in the Pandora and OMI data sets. NO2 columns typically exhibited a low to moderate degree of correlation with surface data in each data set. The results of linear regression analyses for O3 exhibited smaller errors relative to the observations than NO2 regressions. These results suggest that O3 partial column observations from future satellite instruments with sufficient sensitivity to the lower troposphere can be meaningful for surface air quality analysis.
The use of person-fit statistics in computerized adaptive testing
Meijer, R.R.; van Krimpen-Stoop, Edith
2005-01-01
Several person-fit statistics have been proposed to detect item score patterns that do not fit an item response theory model. To classify response patterns as not fitting a model, a distribution of a person-fit statistic is needed. Recently, the null distributions of several fit statistics have been
Testing of a "smart-pebble" for measuring particle transport statistics
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
Segou, M.; Parsons, T.; Ellsworth, W. L.
2012-12-01
We implement a retrospective forecast test specific to the 1989 Loma Prieta sequence and we focus on the comparison between two realizations of the epidemic-type aftershock sequence (ETAS) model and twenty-one models based on Coulomb stress change calculations and rate-and-state theory (CRS). We find that: (1) ETAS models forecast the spatial evolution of seismicity better in the near-source region, (2) CRS models can compete with ETAS models at off-fault regions and short-periods after the mainshock, (3) adopting optimally oriented planes as receivers could lead to better performance for short-time period up to a few days, whereas geologically specified planes should be implemented at long-term forecasting, and (4) CRS models based on shear stress have comparable performance with other CRS models, with the benefit of fewer free parameters involved in the stress calculations. The above results show that physics-based and statistical forecast models are complimentary, and that future forecasts should be combinations of ETAS and CRS models in space and time. We note that the realization in time and space of the CRS models involves a number of critical parameters ('learning' phase seismicity rates, regional stress field, loading rates on faults), which should be retrospectively tested to improve the predictive power of physics-based models.During our experiment the forecast covers Northern California [123.0-121.3°W in longitude 36.4-38.2°N in latitude] in a 2.5 km spatial grid within a 10-day interval following a mainshock, but here we focus on the results related with the post-seismic period of Loma Prieta earthquake. We consider for CRS models a common learning phase (1974-1980) to ensure consistency in our comparison, and we take into consideration stress perturbations imparted by 9 M>5.0 earthquakes between 1980-1989 in Northern California, including the 1988-1989 Lake Ellsman events. ETAS parameters correspond to the maximum likelihood estimations derived after
Jigisha Prahladrai Badheka; Doshi, Pratik M.; Vyas, Ashutosh M.; Nirav Jentilal Kacha; Parmar, Vandana S.
2016-01-01
Background: Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck mo...
Chu, Tsong-Lun [Brookhaven National Lab. (BNL), Upton, NY (United States); Varuttamaseni, Athi [Brookhaven National Lab. (BNL), Upton, NY (United States); Baek, Joo-Seok [Brookhaven National Lab. (BNL), Upton, NY (United States)
2016-11-01
The U.S. Nuclear Regulatory Commission (NRC) encourages the use of probabilistic risk assessment (PRA) technology in all regulatory matters, to the extent supported by the state-of-the-art in PRA methods and data. Although much has been accomplished in the area of risk-informed regulation, risk assessment for digital systems has not been fully developed. The NRC established a plan1 for research on digital systems to identify and develop methods, analytical tools, and regulatory guidance for (1) including models of digital systems in the PRA's of nuclear power plants (NPPs), and, (2) incorporating digital systems in the NRC's risk-informed licensing and oversight activities. Under NRC?s sponsorship, Brookhaven National Laboratory (BNL) explored approaches for addressing the failures of digital instrumentation and control (I and C) systems in the current NPP PRA framework. Specific areas investigated included PRA modeling digital hardware2, development of a philosophical basis for defining software failure3, and identification of desirable attributes of quantitative software reliability methods4 7044. Based on the earlier research, statistical testing is considered a promising method for quantifying software reliability.
Shiraishi, Maresuke; Namba, Ryo; Namikawa, Toshiya; Hazumi, Masashi
2016-01-01
The B-mode polarization in the cosmic microwave background (CMB) anisotropies at large angular scales provides a smoking-gun evidence for the primordial gravitational waves (GWs). It is often stated that a discovery of the GWs establishes the quantum fluctuation of vacuum during the cosmic inflation. Since the GWs could also be generated by source fields, however, we need to check if a sizable signal exists due to such source fields before reaching a firm conclusion when the B-mode is discovered. Source fields of particular types can generate non-Gaussianity (NG) in the GWs. Testing statistics of the B-mode is a powerful way of detecting such NG. As a concrete example, we show a model in which a gauge field sources chiral GWs via a pseudoscalar coupling, and forecast the detection significance at the future CMB satellite LiteBIRD. Effects of residual foregrounds and lensing B-mode are both taken into account. We find the B-mode bispectrum "BBB" is in particular sensitive to the source-field NG, which is detec...
Ramus, Claire; Hovasse, Agnès; Marcellin, Marlène; Hesse, Anne-Marie; Mouton-Barbosa, Emmanuelle; Bouyssié, David; Vaca, Sebastian; Carapito, Christine; Chaoui, Karima; Bruley, Christophe; Garin, Jérôme; Cianférani, Sarah; Ferro, Myriam; Dorssaeler, Alain Van; Burlet-Schiltz, Odile; Schaeffer, Christine; Couté, Yohann; Gonzalez de Peredo, Anne
2016-03-01
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 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.
The Wedge Splitting Test: Influence of Aggregate Size and Water-to-Cement Ratio
Pease, Bradley Justin; Skocek, Jan; Geiker, Mette Rica;
2007-01-01
of various concrete mixtures there are limitations to the current analysis techniques. To date these techniques analyze the result of one WST specimen, thereby providing an estimate of material properties from single result. This paper utilizes a recent improvement to the inverse analysis technique, which......Since the development of the wedge splitting test (WST), techniques have been used to extract material properties that can describe the fracture behavior of the tested materials. Inverse analysis approaches are commonly used to estimate the stress-crack width relationship; which is described...... by the elastic modulus, tensile strength, fracture energy, and the assumed softening behavior. The stress-crack width relation can be implemented in finite element models for computing the cracking behavior of cementitious systems. While inverse analysis provides information about the material properties...
Celestina, Mark L.; Fabian, John C.; Kulkarni, Sameer
2012-01-01
This paper describes a collaborative and cost-shared approach to reducing fuel burn under the NASA Environmentally Responsible Aviation project. NASA and General Electric (GE) Aviation are working together aa an integrated team to obtain compressor aerodynamic data that is mutually beneficial to both NASA and GE Aviation. The objective of the High OPR Compressor Task is to test a single stage then two stages of an advanced GE core compressor using state-of-the-art research instrumentation to investigate the loss mechanisms and interaction effects of embedded transonic highly-loaded compressor stages. This paper presents preliminary results from NASA's in-house multistage computational code, APNASA, in preparation for this advanced transonic compressor rig test.
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
PITR: a small-aspect-ratio, small-major-radius ignition test reactor
Jassby, D.L.; Bolton, R.A.; Brown, D.I.
1978-05-01
The principal objectives of the PITR are to demonstrate the attainment of thermonuclear ignition in D-T, and to develop optimal start-up methods for tokamak power reactors. The design approach is based on minimizing dependence on a central transformer core, which thereby results in a machine of small aspect ratio (A approximately 2 to 2.5) and smaller major radius (R/sub 0/ approximately 2.8 m). Current induction is achieved by a combination of ''leaky OH'' coils, equilibrium-field flux swing, a small central solenoid, and compression. Impurity control is effected by a bundle divertor during the beam-heating phase, and by a cold plasma blanket during the burn. The vacuum vessel is constructed of thin-gauge, double-wall titanium alloy. Sixteen normal-copper TF coils of the compound constant-tension type enable low-stress operation at B/sub max/ = 12.5 T.
Kollonige, D. E.; Thompson, A. M.; Herman, J. R.; Abuhassan, N.; Szykman, J.; Long, R.
2016-12-01
The NASA DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) campaign was a four part field study designed to analyze variability in atmospheric composition across major urban regions and link surface conditions to column abundances captured by remote sensing observations (ie. ground- and satellite-based). To investigate the ability of column information to represent surface air quality, a summary of comparisons between surface mixing ratio data and O3 and NO2 column abundances are presented for all four deployments of DISCOVER-AQ (Baltimore/ Washington DC, MD [2011]; San Joaquin Valley, CA [2013]; Houston, TX [2013]; and Denver, CO [2014]). Data collected at each location by ground-based Pandora spectrometers and Aura/OMI satellite instrument, and planetary boundary layer (PBL) height measurements, also allow direct comparisons between in situ surface NO2 concentrations and surface estimations from Pandora and OMI columns using Kollonige-Knepp method. If PBL height observations are unavailable for a site location, an AIRS (Atmospheric InfraRed Sounder) boundary layer top product will be used to scale the NO2 column abundances for the surface estimations. A statistical analysis of this method across all campaigns as well as case studies under variable meteorological conditions from each deployment are discussed in detail, including clean and polluted conditions in each region. Results from this analysis are valuable to air quality community in preparation for emission inventory evaluations, exceptional event studies, and the upcoming high-resolution satellite observations (ie. TROPOMI and TEMPO).
Kapoor, Nitin; Job, Victoria; Jayaseelan, L.; Rajaratnam, Simon
2012-01-01
Introduction: Although, there are several tests available, not one of them fulfils the criteria of being an ideal screening test. Continuing the search for an ideal screening test, we explored the use of urine spot cortisol-creatinine ratio as a novel method of evaluating patients with Cushing's syndrome. Method: A total of 35 subjects were studied and divided into 3 groups - 15 having cushings syndrome, 15 patients with obesity and 5 normal weight subjects. All patients with cushings syndrome were positive for the other screening tests. Results: The mean (standard deviation) of cortisol:creatinine ratio among the 3 groups (cushings, obese and control subjects) was 36.00(24.74), 7.01(2.73) and 3.49(2.68) respectively. Using the cutoff of 12.27 nano mol/ micro mol(based on data of normal subjects) for the urine cortisol creatinine ratio we get a sensitivity of 93.75% and a specificity of 100%. Also the positive and negative predictive value as calculated with this cutoff is 100% and 93.3% respectively. Conclusion: In this study we found that UCCR is similar in both Obese and Non Obese subjects who did not have cushings syndrome. UCCR is significantly elevated in individuals with Cushing's syndrome as compared to those who do not have cushings syndrome. Also when a cut off of 12.27 nano mol/ micro mol was used this test had a higher sensitivity, however this test had a higher specificity at a cut off of 15.35. PMID:23565435
Nitin Kapoor
2012-01-01
Full Text Available Introduction : Although,there are several tests available, not one of them fulfils the criteria of being an ideal screening test. Continuing the search for an ideal screening test, we explored the use of urine spot cortisol-creatinine ratio as a novel method of evaluating patients with Cushing′s syndrome. Method: A total of 35 subjects were studied and divided into 3 groups - 15 having cushings syndrome, 15 patients with obesity and 5 normal weight subjects. All patients with cushings syndrome were positive for the other screening tests. Results : The mean (standard deviation of cortisol:creatinine ratio among the 3 groups (cushings, obese and control subjects was 36.00(24.74, 7.01(2.73 and 3.49(2.68 respectively. Using the cutoff of 12.27 nano mol/ micro mol(based on data of normal subjects for the urine cortisol creatinine ratio we get a sensitivity of 93.75% and a specificity of 100%. Also the positive and negative predictive value as calculated with this cutoff is 100% and 93.3% respectively. Conclusion: In this study we found that UCCR is similar in both Obese and Non Obese subjects who did not have cushings syndrome. UCCR is significantly elevated in individuals with Cushing′s syndrome as compared to those who do not have cushings syndrome. Also when a cut off of 12.27 nano mol/ micro mol was used this test had a higher sensitivity, however this test had a higher specificity at a cut off of 15.35.
Miecznikowski, Jeffrey C; Damodaran, Senthilkumar; Sellers, Kimberly F; Rabin, Richard A
2010-12-15
Numerous gel-based softwares exist to detect protein changes potentially associated with disease. The data, however, are abundant with technical and structural complexities, making statistical analysis a difficult task. A particularly important topic is how the various softwares handle missing data. To date, no one has extensively studied the impact that interpolating missing data has on subsequent analysis of protein spots. This work highlights the existing algorithms for handling missing data in two-dimensional gel analysis and performs a thorough comparison of the various algorithms and statistical tests on simulated and real datasets. For imputation methods, the best results in terms of root mean squared error are obtained using the least squares method of imputation along with the expectation maximization (EM) algorithm approach to estimate missing values with an array covariance structure. The bootstrapped versions of the statistical tests offer the most liberal option for determining protein spot significance while the generalized family wise error rate (gFWER) should be considered for controlling the multiple testing error. In summary, we advocate for a three-step statistical analysis of two-dimensional gel electrophoresis (2-DE) data with a data imputation step, choice of statistical test, and lastly an error control method in light of multiple testing. When determining the choice of statistical test, it is worth considering whether the protein spots will be subjected to mass spectrometry. If this is the case a more liberal test such as the percentile-based bootstrap t can be employed. For error control in electrophoresis experiments, we advocate that gFWER be controlled for multiple testing rather than the false discovery rate.
Sellers Kimberly F
2010-12-01
Full Text Available Abstract Background Numerous gel-based softwares exist to detect protein changes potentially associated with disease. The data, however, are abundant with technical and structural complexities, making statistical analysis a difficult task. A particularly important topic is how the various softwares handle missing data. To date, no one has extensively studied the impact that interpolating missing data has on subsequent analysis of protein spots. Results This work highlights the existing algorithms for handling missing data in two-dimensional gel analysis and performs a thorough comparison of the various algorithms and statistical tests on simulated and real datasets. For imputation methods, the best results in terms of root mean squared error are obtained using the least squares method of imputation along with the expectation maximization (EM algorithm approach to estimate missing values with an array covariance structure. The bootstrapped versions of the statistical tests offer the most liberal option for determining protein spot significance while the generalized family wise error rate (gFWER should be considered for controlling the multiple testing error. Conclusions In summary, we advocate for a three-step statistical analysis of two-dimensional gel electrophoresis (2-DE data with a data imputation step, choice of statistical test, and lastly an error control method in light of multiple testing. When determining the choice of statistical test, it is worth considering whether the protein spots will be subjected to mass spectrometry. If this is the case a more liberal test such as the percentile-based bootstrap t can be employed. For error control in electrophoresis experiments, we advocate that gFWER be controlled for multiple testing rather than the false discovery rate.
Honarmand, Azim; Safavi, Mohammadreza; Ansari, Narges
2014-01-01
Failed intubation is imperative source of anesthetic interrelated patient's mortality. The aim of this present study was to compare the ability to predict difficult visualization of the larynx from the following pre-operative airway predictive indices, in isolation and combination: Modified Mallampati test (MMT), the ratio of height to thyromental distance (RHTMD), hyomental distance ratios (HMDR), and the upper-lip-bite test (ULBT). We collected data on 525 consecutive patients scheduled for elective surgery under general anesthesia requiring endotracheal intubation and then evaluated all four factors before surgery. A skilled anesthesiologist, not imparted of the noted pre-operative airway assessment, did the laryngoscopy and rating (as per Cormack and Lehane's classification). Sensitivity, specificity, and positive predictive value for every airway predictor in isolation and in combination were established. The most sensitive of the single tests was ULBT with a sensitivity of 90.2%. The hyomental distance extreme of head extension was the least sensitive of the single tests with a sensitivity of 56.9. The HMDR had sensitivity 86.3%. The ULBT had the highest negative predictive value: And the area under a receiver-operating characteristic curve (AUC of ROC curve) among single predictors. The AUC of ROC curve for ULBT, HMDR and RHTMD was significantly more than for MMT (P 0.05). The HMDR is comparable with RHTMD and ULBT for prediction of difficult laryngoscopy in the general population, but was significantly more than for MMT.
Influence of counting methodology on erythrocyte ratios in the mouse micronucleus test.
LeBaron, Matthew J; Schisler, Melissa R; Torous, Dorothea K; Dertinger, Stephen D; Gollapudi, B Bhaskar
2013-04-01
The mammalian erythrocyte micronucleus test is widely used to investigate the potential interaction of a test substance with chromosomes or mitotic apparatus of replicating erythroblasts. In addition to the primary endpoint, micronucleated erythrocyte frequency, the proportion of immature erythrocytes is measured to assess the influence of treatment on erythropoiesis. The guideline recommendation for an acceptable limit of the immature erythrocyte fraction of not < 20% of the controls was based on traditional scoring methods that consider RNA content. Flow-based sample analysis (e.g., MicroFlow®) characterizes a subpopulation of RNA-containing reticulocytes (RETs) based on CD71 (transferrin receptor) expression. As CD71+ cells represent a younger cohort of RETs, we hypothesized that this subpopulation may be more responsive than the RNA+ fraction for acute exposures. This study evaluated RET population in the peripheral blood of two strains of mice treated by oral gavage with three clastogens (cyclophosphamide, N-ethyl-N-nitrosourea, and methyl methanesulfonate). Although CD71+ frequencies correlated with RNA-based counts, the relative treatment-related reductions were substantially greater. Accordingly, when using the flow cytometry-based CD71+ values for scoring RETs in an acute treatment design, it is suggested that a target value ≥ 5% CD71+ reticulocytes (i.e., 95% depression in reticulocytes proportion) be considered as acceptable for a valid assay.
Jigisha Prahladrai Badheka
2016-01-01
Full Text Available Background: Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT and ratio of height to thyromental distance (RHTMD are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck movements, and horizontal length of mandible for predicting difficult intubation. Materials and Methods: In this single blinded, prospective, observational study involving 170 adult patients of either sex belonging to American Society of Anesthesiologists physical Status I-III scheduled to undergo general anesthesia were recruited. All patients were subjected to the preoperative airway assessment and, the above parameters were recorded correlated with Cormack and Lehane grade and analyzed. The number of intubation attempts and use of intubation aids were also noted. Results: ULBT and RHTMD had highest sensitivity (96.64%, 90.72%, specificity (82.35%, 80.39%, positive predictive value (92.74%, 91.53%, and negative predictive value (91.3%, 78.8%, respectively, compared to other parameters. While odds ratio and likelihood ratio >1 for all the tests. Conclusion: ULBT can be used as a simple bedside screening test for prediction of difficult intubation, but it should be combined with other airway assessment tests for better airway predictability. RHTMD can also be used as an acceptable alternative.
Badheka, Jigisha Prahladrai; Doshi, Pratik M; Vyas, Ashutosh M; Kacha, Nirav Jentilal; Parmar, Vandana S
2016-01-01
Various anatomical measurements and noninvasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Upper lip bite test (ULBT) and ratio of height to thyromental distance (RHTMD) are claimed to have high predictability. Hence, we have conducted this study to compare the predictive value of ULBT and RHTMD with the following parameters: Mallampati grading, inter-incisor gap, thyromental distance, sternomental distance, head and neck movements, and horizontal length of mandible for predicting difficult intubation. In this single blinded, prospective, observational study involving 170 adult patients of either sex belonging to American Society of Anesthesiologists physical Status I-III scheduled to undergo general anesthesia were recruited. All patients were subjected to the preoperative airway assessment and, the above parameters were recorded correlated with Cormack and Lehane grade and analyzed. The number of intubation attempts and use of intubation aids were also noted. ULBT and RHTMD had highest sensitivity (96.64%, 90.72%), specificity (82.35%, 80.39%), positive predictive value (92.74%, 91.53%), and negative predictive value (91.3%, 78.8%), respectively, compared to other parameters. While odds ratio and likelihood ratio >1 for all the tests. ULBT can be used as a simple bedside screening test for prediction of difficult intubation, but it should be combined with other airway assessment tests for better airway predictability. RHTMD can also be used as an acceptable alternative.
Lani, Frédéric; 6th International Conference on Fatigue of Composite ICFC2015
2015-01-01
A woven CFRP composite laminate has been thoroughly characterized under fatigue. Over 150 tests were performed in order to address the effect of sample geometry (Open Hole Tension, Open Hole Compression, Plain Compression, …), testing frequency (5Hz, 30Hz) with and without cooling system, load ratio (R=10., R=-1., R=0.1), temperature (RT and 120°C), moisture intake (50% RH and 85+% RH at RT), notch (Open Hole Vs. Plain Specimen), stacking sequence (3 different stacking sequences) on the measu...
Jones, Andrew T.
2011-01-01
Practitioners often depend on item analysis to select items for exam forms and have a variety of options available to them. These include the point-biserial correlation, the agreement statistic, the B index, and the phi coefficient. Although research has demonstrated that these statistics can be useful for item selection, no research as of yet has…
Sub-poissonian statistics as an experimental test for the contextuality of quantum theory
Arnoldus, H.F.; Dieks, Dennis; Nienhuis, G.
1984-01-01
It is argued that the phenomenon of sub-poissonian statistics can be regarded as experimental evidence for the contextual character of quantum theory. To this end, it is shown that the statistics predicted by non-contextual hidden-variable theories must satisfy certain inequalities which are a kind
The Effects of Pre-Lecture Quizzes on Test Anxiety and Performance in a Statistics Course
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…
The Effects of Pre-Lecture Quizzes on Test Anxiety and Performance in a Statistics Course
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…
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…
Two-Compartment Photoelectrochemical Reactors Tested under various solar Light Concentration ratios
Fernandez-Ibanez, P.; Malato, S. [Plataforma Solar de Almeria. CIEMAT (Spain)
1999-07-01
A new type of photo reactor, made of a cylindrical photo anode placed around an inner comportment, has been adapted to the compound parabolic (CPC's) and to the parabolic trough (PTC, Helioman) solar collectors. The photoelectrochemical performances of such two-compartment photo reactors are noticeably improved with respect to those previously obtained with photo reactors having flat photoanodes and a single compartment. The abatement of model pollutants shows up to threefold higher organic oxidation rates compared to Ti O{sub 2} slurries tested in the same experimental conditions. Clearly, charge separation is much better when an external electrochemical bias is applied to Ti/Ti O{sub 2} photoanodes under irradiation. (Author) 8 refs.
Shiraishi, Maresuke; Hikage, Chiaki; Namba, Ryo; Namikawa, Toshiya; Hazumi, Masashi
2016-08-01
The B -mode polarization in the cosmic microwave background (CMB) anisotropies at large angular scales provides compelling evidence for the primordial gravitational waves (GWs). It is often stated that a discovery of the GWs establishes the quantum fluctuation of vacuum during the cosmic inflation. Since the GWs could also be generated by source fields, however, we need to check if a sizable signal exists due to such source fields before reaching a firm conclusion when the B mode is discovered. Source fields of particular types can generate non-Gaussianity (NG) in the GWs. Testing statistics of the B mode is a powerful way of detecting such NG. As a concrete example, we show a model in which gauge field sources chiral GWs via a pseudoscalar coupling and forecast the detection significance at the future CMB satellite LiteBIRD. Effects of residual foregrounds and lensing B mode are both taken into account. We find the B -mode bispectrum "BBB" is in particular sensitive to the source-field NG, which is detectable at LiteBIRD with a >3 σ significance. Therefore the search for the BBB will be indispensable toward unambiguously establishing quantum fluctuation of vacuum when the B mode is discovered. We also introduced the Minkowski functional to detect the NGs. While we find that the Minkowski functional is less efficient than the harmonic-space bispectrum estimator, it still serves as a useful cross-check. Finally, we also discuss the possibility of extracting clean information on parity violation of GWs and new types of parity-violating observables induced by lensing.
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 a
Evaluating Statistical Targets for Assembling Parallel Mixed-Format Test Forms
Debeer, Dries; Ali, Usama S.; van Rijn, Peter W.
2017-01-01
Test assembly is the process of selecting items from an item pool to form one or more new test forms. Often new test forms are constructed to be parallel with an existing (or an ideal) test. Within the context of item response theory, the test information function (TIF) or the test characteristic curve (TCC) are commonly used as statistical…
An objective statistical test for eccentricity forcing of Oligo-Miocene climate
Proistosescu, C.; Huybers, P.; Maloof, A. C.
2008-12-01
We seek a maximally objective test for the presence of orbital features in Oligocene and Miocene δ18O records from marine sediments. Changes in Earth's orbital eccentricity are thought to be an important control on the long term variability of climate during the Oligocene and Miocene Epochs. However, such an important control from eccentricity is surprising because eccentricity has relatively little influence on Earth's annual average insolation budget. Nevertheless, if significant eccentricity variability is present, it would provide important insight into the operation of the climate system at long timescales. Here we use previously published data, but using a chronology which is initially independent of orbital assumptions, to test for the presence of eccentricity period variability in the Oligocene/Miocene sediment records. In contrast to the sawtooth climate record of the Pleistocene, the Oligocene and Miocene climate record appears smooth and symmetric and does not reset itself every hundred thousand years. This smooth variation, as well as the time interval spanning many eccentricity periods makes Oligocene and Miocene paleorecords very suitable for evaluating the importance of eccentricity forcing. First, we construct time scales depending only upon the ages of geomagnetic reversals with intervening ages linearly interpolated with depth. Such a single age-depth relationship is, however, too uncertain to assess whether orbital features are present. Thus, we construct a second depth-derived age-model by averaging ages across multiple sediment cores which have, at least partly, independent accumulation rate histories. But ages are still too uncertain to permit unambiguous detection of orbital variability. Thus we employ limited tuning assumptions and measure the degree by orbital period variability increases using spectral power estimates. By tuning we know that we are biasing the record toward showing orbital variations, but we account for this bias in our
Jovanović, Boris
2015-05-01
Titanium dioxide nanoparticles are photoactive and produce reactive oxygen species under natural sunlight. Reactive oxygen species can be detrimental to many organisms, causing oxidative damage, cell injury, and death. Most studies investigating TiO2 nanoparticle toxicity did not consider photoactivation and performed tests either in dark conditions or under artificial lighting that did not simulate natural irradiation. The present study summarizes the literature and derives a phototoxicity ratio between the results of nano-titanium dioxide (nano-TiO2 ) experiments conducted in the absence of sunlight and those conducted under solar or simulated solar radiation (SSR) for aquatic species. Therefore, the phototoxicity ratio can be used to correct endpoints of the toxicity tests with nano-TiO2 that were performed in absence of sunlight. Such corrections also may be important for regulators and risk assessors when reviewing previously published data. A significant difference was observed between the phototoxicity ratios of 2 distinct groups: aquatic species belonging to order Cladocera, and all other aquatic species. Order Cladocera appeared very sensitive and prone to nano-TiO2 phototoxicity. On average nano-TiO2 was 20 times more toxic to non-Cladocera and 1867 times more toxic to Cladocera (median values 3.3 and 24.7, respectively) after illumination. Both median value and 75% quartile of the phototoxicity ratio are chosen as the most practical values for the correction of endpoints of nano-TiO2 toxicity tests that were performed in dark conditions, or in the absence of sunlight.
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.
Christensen, Rune Haubo Bojesen; Ennis, John M.; Ennis, Daniel M.
2014-01-01
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...... high a type I error rate if the identicality norm is not estimated from a very large sample size. We then compare five χ2 tests of paired preference data with a no preference option in terms of type I error and power in a series of scenarios. In particular, we identify two tests that are well behaved...... for sample sizes typical of recent research and have high statistical power. One of these tests has the advantage that it can be decomposed for more insightful analyses in a fashion similar to that of ANOVA F-tests. The benefits are important because they enable more informed business decisions, particularly...
Tests for, origins of, and corrections to non-Gaussian statistics. The dipole-flip model.
Schile, Addison J; Thompson, Ward H
2017-04-21
Linear response approximations are central to our understanding and simulations of nonequilibrium statistical mechanics. Despite the success of these approaches in predicting nonequilibrium dynamics, open questions remain. Laird and Thompson [J. Chem. Phys. 126, 211104 (2007)] previously formalized, in the context of solvation dynamics, the connection between the static linear-response approximation and the assumption of Gaussian statistics. The Gaussian statistics perspective is useful in understanding why linear response approximations are still accurate for perturbations much larger than thermal energies. In this paper, we use this approach to address three outstanding issues in the context of the "dipole-flip" model, which is known to exhibit nonlinear response. First, we demonstrate how non-Gaussian statistics can be predicted from purely equilibrium molecular dynamics (MD) simulations (i.e., without resort to a full nonequilibrium MD as is the current practice). Second, we show that the Gaussian statistics approximation may also be used to identify the physical origins of nonlinear response residing in a small number of coordinates. Third, we explore an approach for correcting the Gaussian statistics approximation for nonlinear response effects using the same equilibrium simulation. The results are discussed in the context of several other examples of nonlinear responses throughout the literature.
Toscanini, Ulises; Salas, Antonio; García-Magariños, Manuel; Gusmão, Leonor; Raimondi, Eduardo
2010-01-01
A simulation-based analysis was carried out to investigate the potential effects of population substructure in paternity testing in Argentina. The study was performed by evaluating paternity indexes (PI) calculated from different simulated pedigree scenarios and using 15 autosomal short tandem repeats (STRs) from eight Argentinean databases. The results show important statistically significant differences between PI values depending on the dataset employed. These differences are more dramatic when considering Native American versus urban populations. This study also indicates that the use of Fst to correct for the effect of population stratification on PI might be inappropriate because it cannot account for the particularities of single paternity cases.
DAVID BELLAR
2016-10-01
Full Text Available The purpose of the present investigation was to examine the ratio between total cO2 expiration and O2 consumption to vO2max. Twenty-six male (vO2 max: 55.4± 8.3 ml O2/kg*min and thirty- five female (vO2 max: 44.1± 8.1 ml O2/kg*min recreationally active adults volunteered. The participants underwent a custom ramped treadmill protocol (gXT with expired gases monitored. Third order polynomial regression was undertaken for the vO2 and vcO2 by time (r>0.950. regression equations were integrated from 60seconds after the start of the test (to negate any initial hyperventilation until vO2 max. This area under the curve calculation was equal to the total accumulated expired cO2 and consumed O2. The ratio of total cO2 to O2 was calculated (auc ratio. Data analysis was undertaken using multiple linear regression analysis. The model included gender, rer at vO2 max and auc ratio as predictors and relative vO2 max as the outcome. The model was significant with predictor variable gender (b =0.582, p<0.001 and auc ratio (b=-0.298, p=0.019 significant in the model. Based upon these results it would appear that individuals who are more fit relying more heavily on oxidative pathways throughout the course of a GXT.
M Nandhini; S N Sivanandam
2015-09-01
Health care data diagnosis is a significant task that needs to be executed precisely, which requires much experience and domain-knowledge. Traditional symptoms-based disease diagnosis may perhaps lead to false presumptions. In recent times, Associative Classification (AC), the combination of association rule mining and classification has received attention in health care applications which desires maximum accuracy. Though several AC techniques exist, they lack in generating quality rules for building efficient associative classifier. This paper aims to enhance the accuracy of the existing CPAR (Classification based on Predictive Association Rule) algorithm by generating quality rules using Gain Ratio. Mostly, health care applications deal with high dimensional datasets. Existence of high dimensions causes unfair estimates in disease diagnosis. Dimensionality reduction is commonly applied as a preprocessing step before classification task to improve classifier accuracy. It eliminates redundant and insignificant dimensions by keeping good ones without information loss. In this work, dimensionality reductions by T-test and reduct sets (or simply reducts) are performed as preprocessing step before CPAR and CPAR using Gain Ratio (CPAR-GR) algorithms. An investigation was also performed to determine the impact of T-test and reducts on CPAR and CPAR-GR. This paper synthesizes the existing work carried out in AC, and also discusses the factors that influence the performance of CPAR and CPAR-GR. Experiments were conducted using six health care datasets from UCI machine learning repository. Based on the experiments, CPAR-GR with T-test yields better classification accuracy than CPAR.
Azim Honarmand
2014-01-01
Full Text Available Background: Failed intubation is imperative source of anesthetic interrelated patient′s mortality. The aim of this present study was to compare the ability to predict difficult visualization of the larynx from the following pre-operative airway predictive indices, in isolation and combination: Modified Mallampati test (MMT, the ratio of height to thyromental distance (RHTMD, hyomental distance ratios (HMDR, and the upper-lip-bite test (ULBT. Materials and Methods: We collected data on 525 consecutive patients scheduled for elective surgery under general anesthesia requiring endotracheal intubation and then evaluated all four factors before surgery. A skilled anesthesiologist, not imparted of the noted pre-operative airway assessment, did the laryngoscopy and rating (as per Cormack and Lehane′s classification. Sensitivity, specificity, and positive predictive value for every airway predictor in isolation and in combination were established. Results: The most sensitive of the single tests was ULBT with a sensitivity of 90.2%. The hyomental distance extreme of head extension was the least sensitive of the single tests with a sensitivity of 56.9. The HMDR had sensitivity 86.3%. The ULBT had the highest negative predictive value: And the area under a receiver-operating characteristic curve (AUC of ROC curve among single predictors. The AUC of ROC curve for ULBT, HMDR and RHTMD was significantly more than for MMT (P 0.05. Conclusion: The HMDR is comparable with RHTMD and ULBT for prediction of difficult laryngoscopy in the general population, but was significantly more than for MMT.
Dopfer, D.D.V.; Maassen, C.B.M.; Achterberg, R.P.; Giessen, van der J.W.B.; Teunis, P.; Buist, W.G.; Molina, V.; Guarnera, E.; Gonzales, M.; Krivokapich, S.; Rodriguez, M.; Peralta, J.L.; Trabattoni, H.; Larrieu, E.; Engel, B.
2006-01-01
To evaluate the usefulness of serological tests applied to monitor Trichinella free herds, Bayesian methodology was used to estimate the diagnostic test parameters: sensitivity, specificity and prevalence in the absence of a Gold Standard test. In the absence of Dutch serum samples for positive pigs
Løkkegaard, Thomas; Pedersen, Tina Heidi; Lind, Bent
2015-01-01
INTRODUCTION: Oral anticoagulation treatment (OACT)with warfarin is common in general practice. Increasingly,international normalised ratio (INR) point of care testing(POCT) is being used to manage patients. The aim of thisstudy was to describe and analyse the quality of OACT withwarfarin...... in the management of patients in warfarintreatment provided good quality of care. Sampling intervaland diagnostic coding were significantly correlated withtreatment quality. FUNDING: The study received financial support from theSarah Krabbe Foundation, the General Practitioners’ Educationand Development Foundation...
Association testing for next-generation sequencing data using score statistics
Skotte, Line; Korneliussen, Thorfinn Sand; Albrechtsen, Anders
2012-01-01
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...... 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...
Batsidis, Apostolos; Pardo, Leandro; Zografos, Konstantinos
2011-01-01
This paper studies the change point problem for a general parametric, univariate or multivariate family of distributions. An information theoretic procedure is developed which is based on general divergence measures for testing the hypothesis of the existence of a change. For comparing the accuracy of the new test-statistic a simulation study is performed for the special case of a univariate discrete model. Finally, the procedure proposed in this paper is illustrated through a classical change-point example.
Nielsen, Allan Aasbjerg; Conradsen, Knut; Skriver, Henning
2016-01-01
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...
Monroe, Scott; Cai, Li
2015-01-01
This research is concerned with two topics in assessing model fit for categorical data analysis. The first topic involves the application of a limited-information overall test, introduced in the item response theory literature, to structural equation modeling (SEM) of categorical outcome variables. Most popular SEM test statistics assess how well the model reproduces estimated polychoric correlations. In contrast, limited-information test statistics assess how well the underlying categorical data are reproduced. Here, the recently introduced C2 statistic of Cai and Monroe (2014) is applied. The second topic concerns how the root mean square error of approximation (RMSEA) fit index can be affected by the number of categories in the outcome variable. This relationship creates challenges for interpreting RMSEA. While the two topics initially appear unrelated, they may conveniently be studied in tandem since RMSEA is based on an overall test statistic, such as C2. The results are illustrated with an empirical application to data from a large-scale educational survey.
Oshima, T. C.; Raju, Nambury S.; Nanda, Alice O.
2006-01-01
A new item parameter replication method is proposed for assessing the statistical significance of the noncompensatory differential item functioning (NCDIF) index associated with the differential functioning of items and tests framework. In this new method, a cutoff score for each item is determined by obtaining a (1-alpha ) percentile rank score…
Nielsen, Morten Ørregaard
reflects the parameter chosen to implement the test, and (iii) since the asymptotic distribution depends on d and the test remains consistent for all d > 0, it is possible to analyze the power of the test for different values of d. The usual Phillips-Perron or Dickey-Fuller type tests are indexed...... good size properties, with finite sample power that is higher than that of Breitung's (2002) test and even rivals the (nearly) optimal parametric GLS detrended augmented Dickey-Fuller test with lag length chosen by an information criterion....
Comment on a Wilcox Test Statistic for Comparing Means When Variances Are Unequal.
Hsiung, Tung-Hsing; And Others
1994-01-01
The alternative proposed by Wilcox (1989) to the James second-order statistic for comparing population means when variances are heterogeneous can sometimes be invalid. The degree to which the procedure is invalid depends on differences in sample size, the expected values of the observations, and population variances. (SLD)
Novick, Melvin R.
This project is concerned with the development and implementation of some new statistical techniques that will facilitate a continuing input of information about the student to the instructional manager so that individualization of instruction can be managed effectively. The source of this informational input is typically a short…
Testing statistical significance scores of sequence comparison methods with structure similarity
Hulsen, T.; Vlieg, J. de; Leunissen, J.A.M.; Groenen, P.M.
2006-01-01
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 s
Testing statistical significance scores of sequence comparison methods with structure similarity
Hulsen, T.; Vlieg, de J.; Leunissen, J.A.M.; Groenen, P.
2006-01-01
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
Pratibha Jain Shah
2013-01-01
Full Text Available Background: Various anatomical measurements and non-invasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Recently introduced "Upper lip bite test" (ULBT and "Ratio of height to Thyromental distance" (RHTMD are claimed to have high predictability. We conducted a study to compare the Predictive Value of ULBT and RHTMD with Mouth opening (Inter-Incisor gap (IIG, Modified Mallampatti Test (MMT, Head and neck movement (HNM and Thyromental Distance (TMD for Difficult Laryngoscopy. Materials and Methods: In this prospective, single blinded observational study, 480 adult patients of either sex, ASA grade I and II were assessed and graded for ULBT, RHTMD, TMD, MMT, IIG, and HNM according to standard methods and correlated with the Cormack and Lehane grade. Results: ULBT and RHTMD had highest sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio, i.e., 74.63%, 91.53%, 58.82%, 95.7%, 31.765 and 71.64%, 92.01%, 59.26%, 95.24%, 8.96 respectively, compared to TMD, MMT, IIG and HNM. Conclusions: ULBT is the best predictive test for difficult laryngoscopy in apparently normal patients but RHTMD can also be used as an acceptable alternative.
Shah, Pratibha Jain; Dubey, Kamta Prasad; Yadav, Jai Prakash
2013-04-01
Various anatomical measurements and non-invasive clinical tests, singly or in various combinations can be performed to predict difficult intubation. Recently introduced "Upper lip bite test" (ULBT) and "Ratio of height to Thyromental distance" (RHTMD) are claimed to have high predictability. We conducted a study to compare the Predictive Value of ULBT and RHTMD with Mouth opening (Inter-Incisor gap) (IIG), Modified Mallampatti Test (MMT), Head and neck movement (HNM) and Thyromental Distance (TMD) for Difficult Laryngoscopy. In this prospective, single blinded observational study, 480 adult patients of either sex, ASA grade I and II were assessed and graded for ULBT, RHTMD, TMD, MMT, IIG, and HNM according to standard methods and correlated with the Cormack and Lehane grade. ULBT and RHTMD had highest sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio, i.e., 74.63%, 91.53%, 58.82%, 95.7%, 31.765 and 71.64%, 92.01%, 59.26%, 95.24%, 8.96 respectively, compared to TMD, MMT, IIG and HNM. ULBT is the best predictive test for difficult laryngoscopy in apparently normal patients but RHTMD can also be used as an acceptable alternative.
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.
Using Cumulative Sum Statistics to Detect Inconsistencies in Unproctored Internet Testing
Tendeiro, Jorge N.; Meijer, Rob R.; Schakel, Lolle; Maij-de Meij, Annette M.
2013-01-01
Unproctored Internet Testing (UIT) is becoming more popular in personnel recruitment and selection. A drawback of UIT is that cheating is easy and, therefore, a proctored test is often administered after an UIT procedure. To detect inconsistent test scores from UIT, a cumulative sum procedure (CUSUM
Hilborn, Robert C.
1997-04-01
The connection between the spin of particles and the permutation symmetry ("statistics") of multiparticle states lies at the heart of much of atomic, molecular, condensed matter, and nuclear physics. The spin-statistics theorem of relativistic quantum field theory seems to provide a theoretical basis for this connection. There are, however, loopholes (O. W. Greenberg, Phys. Rev. D 43, 4111 (1991).) that allow for a field theory of identical particles whose statistics interpolate smoothly between that of bosons and fermions. Thus, it is up to experiment to reveal how closely nature follows the usual spin- statistics connection. After reviewing experiments that provide stringent limits on possible violations of the spin-statistics connection for electrons, I shall describe recent analogous experiments for spin-0 particles (R. C. Hilborn and C. L. Yuca, Phys. Rev. Lett. 76, 2844 (1996).) using diode laser spectroscopy of the A-band of molecular oxygen near 760 nm. These experiments show that the probability of finding two ^16O nuclei (spin-0 particles) in an antisymmetric state is less than 1ppm. I shall also discuss proposals to test the spin-statistics connection for photons.
Romulus Costache; Liliana Zaharia
2017-06-01
Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 km2), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results’ testing (validating area) and (ii) plotting the ROC (receiver operating
Costache, Romulus; Zaharia, Liliana
2017-06-01
Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 km2), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results' testing (validating area) and (ii) plotting the ROC (receiver operating
Ingber, L
1998-01-01
A series of papers has developed a statistical mechanics of neocortical interactions (SMNI), deriving aggregate behavior of experimentally observed columns of neurons from statistical electrical-chemical properties of synaptic interactions. While not useful to yield insights at the single neuron level, SMNI has demonstrated its capability in describing large-scale properties of short-term memory and electroencephalographic (EEG) systematics. The necessity of including nonlinear and stochastic structures in this development has been stressed. Sets of EEG and evoked potential data were fit, collected to investigate genetic predispositions to alcoholism and to extract brain signatures of short-term memory. Adaptive Simulated Annealing (ASA), a global optimization algorithm, was used to perform maximum likelihood fits of Lagrangians defined by path integrals of multivariate conditional probabilities. Canonical momenta indicators (CMI) are thereby derived for individual's EEG data. The CMI give better signal recog...
Statistical tests with accurate size and power for balanced linear mixed models.
Muller, Keith E; Edwards, Lloyd J; Simpson, Sean L; Taylor, Douglas J
2007-08-30
The convenience of linear mixed models for Gaussian data has led to their widespread use. Unfortunately, standard mixed model tests often have greatly inflated test size in small samples. Many applications with correlated outcomes in medical imaging and other fields have simple properties which do not require the generality of a mixed model. Alternately, stating the special cases as a general linear multivariate model allows analysing them with either the univariate or multivariate approach to repeated measures (UNIREP, MULTIREP). Even in small samples, an appropriate UNIREP or MULTIREP test always controls test size and has a good power approximation, in sharp contrast to mixed model tests. Hence, mixed model tests should never be used when one of the UNIREP tests (uncorrected, Huynh-Feldt, Geisser-Greenhouse, Box conservative) or MULTIREP tests (Wilks, Hotelling-Lawley, Roy's, Pillai-Bartlett) apply. Convenient methods give exact power for the uncorrected and Box conservative tests. Simulations demonstrate that new power approximations for all four UNIREP tests eliminate most inaccuracy in existing methods. In turn, free software implements the approximations to give a better choice of sample size. Two repeated measures power analyses illustrate the methods. The examples highlight the advantages of examining the entire response surface of power as a function of sample size, mean differences, and variability.
Gastwirth, Joseph L.
1987-01-01
The increased use of screening tests for drug use or antibodies to the HTLV-III (AIDS) virus, as well as pre-employment polygraph testing, has raised concerns about the reliability of the results of these procedures. This paper reviews the mathematical model underlying the analysis of data from screening tests. In addition to the known formulas for the proportion of positive (negative) classifications that are correct, we provide a large sample approximation to their standard errors. The resu...
2007-11-02
specification of one of the tests coming from the DIEHARD 69 [1] battery of tests. It is based on the result of Kovalenko (1972) and also formulated in Marsaglia ...References for Test [1] George Marsaglia , DIEHARD: a battery of tests of randomness. http://stat.fsu.edu/˜geo/diehard.html. [2] I. N. Kovalenko (1972...Distribution of the linear rank of a random ma- trix,” Theory of Probability and its Applications. 17, pp. 342-346. [3] G. Marsaglia and L. H. Tsay
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…
Munshi, D; Melott, A L; Munshi, Dipak; Coles, Peter; Melott, Adrian L.
1999-01-01
We develop a diagrammatic technique to represent the multi-point cumulative probability density function (CPDF) of mass fluctuations in terms of the statistical properties of individual collapsed objects and relate this to other statistical descriptors such as cumulants, cumulant correlators and factorial moments. We use this approach to establish key scaling relations describing various measurable statistical quantities if clustering follows a simple general scaling ansatz, as expected in hierarchical models. We test these detailed predictions against high-resolution numerical simulations. We show that, when appropriate variables are used, the count probability distribution function (CPDF) and void probability distribution function (VPF) shows clear scaling properties in the non-linear regime. Generalising the results to the two-point count probability distribution function (2CPDF), and the bivariate void probability function (2VPF) we find good match with numerical simulations. We explore the behaviour of t...
Tom Leininger
2001-03-31
Reliable measurement of gasifier reaction chamber temperature is important for the proper operation of slagging, entrained-flow gasification processes. Historically, thermocouples have been used as the main measurement technique, with the temperature inferred from syngas methane concentration being used as a backup measurement. While these have been sufficient for plant operation in many cases, both techniques suffer from limitations. The response time of methane measurements is too slow to detect rapid upset conditions, and thermocouples are subject to long-term drift, as well as slag attack, which eventually leads to failure of the thermocouple. Texaco's Montebello Technology Center (MTC) has developed an infrared ratio pyrometer system for measuring gasifier reaction chamber temperature. This system has a faster response time than both methane and thermocouples, and has been demonstrated to provide reliable temperature measurements for longer periods of time when compared to thermocouples installed in the same MTC gasifier. In addition, the system can be applied to commercial gasifiers without any significant scale-up issues. The major equipment items, the purge system, and the safety shutdown system in a commercial plant are essentially identical to the prototypes at MTC. The desired result of this DOE program is ''a bench-scale prototype, either assembled or with critical components (laboratory) tested in a convincing manner.'' The prototype of the pyrometer system (including gasifier optical access port) that was designed, assembled and tested for this program, has had previous prototypes that have been built and successfully tested under actual coal and coke gasification conditions in three pilot units at MTC. It was the intent of the work performed under the auspices of this program to review and update the existing design, and to fabricate and bench test an updated system that can be field tested in one or more commercial gasifiers
Multilevel Factor Analysis by Model Segregation: New Applications for Robust Test Statistics
Schweig, Jonathan
2014-01-01
Measures of classroom environments have become central to policy efforts that assess school and teacher quality. This has sparked a wide interest in using multilevel factor analysis to test measurement hypotheses about classroom-level variables. One approach partitions the total covariance matrix and tests models separately on the…
WANG Ronghua; FEI Heliang
2004-01-01
In this note, the tampered failure rate model is generalized from the step-stress accelerated life testing setting to the progressive stress accelerated life testing for the first time. For the parametric setting where the scale parameter satisfying the equation of the inverse power law is Weibull, maximum likelihood estimation is investigated.
Hybrid Statistical Testing for Nuclear Material Accounting Data and/or Process Monitoring Data
Ticknor, Lawrence O. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hamada, Michael Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sprinkle, James K. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burr, Thomas Lee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-04-14
The two tests employed in the hybrid testing scheme are Page’s cumulative sums for all streams within a Balance Period (maximum of the maximums and average of the maximums) and Crosier’s multivariate cumulative sum applied to incremental cumulative sums across Balance Periods. The role of residuals for both kinds of data is discussed.
Deacon, S. Helene; Leung, Dilys
2013-01-01
This study tested the diverging predictions of recent theories of children's learning of spelling regularities. We asked younger (Grades 1 and 2) and older (Grades 3 and 4) elementary school-aged children to choose the correct endings for words that varied in their morphological structure. We tested the impacts of semantic frequency by…
El Korso Mohammed
2011-01-01
Full Text Available Abstract The statistical resolution limit (SRL, which is defined as the minimal separation between parameters to allow a correct resolvability, is an important statistical tool to quantify the ultimate performance for parametric estimation problems. In this article, we generalize the concept of the SRL to the multidimensional SRL (MSRL applied to the multidimensional harmonic retrieval model. In this article, we derive the SRL for the so-called multidimensional harmonic retrieval model using a generalization of the previously introduced SRL concepts that we call multidimensional SRL (MSRL. We first derive the MSRL using an hypothesis test approach. This statistical test is shown to be asymptotically an uniformly most powerful test which is the strongest optimality statement that one could expect to obtain. Second, we link the proposed asymptotic MSRL based on the hypothesis test approach to a new extension of the SRL based on the Cramér-Rao Bound approach. Thus, a closed-form expression of the asymptotic MSRL is given and analyzed in the framework of the multidimensional harmonic retrieval model. Particularly, it is proved that the optimal MSRL is obtained for equi-powered sources and/or an equi-distributed number of sensors on each multi-way array.
De Meeûs, Thierry
2014-03-01
In population genetics data analysis, researchers are often faced to the problem of decision making from a series of tests of the same null hypothesis. This is the case when one wants to test differentiation between pathogens found on different host species sampled from different locations (as many tests as number of locations). Many procedures are available to date but not all apply to all situations. Finding which tests are significant or if the whole series is significant, when tests are independent or not do not require the same procedures. In this note I describe several procedures, among the simplest and easiest to undertake, that should allow decision making in most (if not all) situations population geneticists (or biologists) should meet, in particular in host-parasite systems. Copyright © 2014 Elsevier B.V. All rights reserved.
Maczka Paulina
2014-06-01
Full Text Available Dissolution tests of amlodipine and perindopril from their fixed dose formulations were performed in 900 mL of phosphate buffer of pH 5.5 at 37°C using the paddle apparatus. Then, two simple and rapid derivative spectrophotometric methods were used for the quantitative measurements of amlodipine and perindopril. The first method was zero crossing first derivative spectrophotometry in which measuring of amplitudes at 253 nm for amlodipine and 229 nm for perindopril were used. The second method was ratio derivative spectrophotometry in which spectra of amlodipine over the linearity range were divided by one selected standard spectrum of perindopril and then amplitudes at 242 nm were measured. Similarly, spectra of perindopril were divided by one selected standard spectrum of amlodipine and then amplitudes at 298 nm were measured. Both of the methods were validated to meet official requirements and were demonstrated to be selective, precise and accurate. Since there is no official monograph for these drugs in binary formulations, the dissolution tests and quantification procedure presented here can be used as a quality control test for amlodipine and perindopril in respective dosage forms.
Ying Bi
2017-02-01
Full Text Available An active control technique utilizing piezoelectric actuators to alleviate gust-response loads of a large-aspect-ratio flexible wing is investigated. Piezoelectric materials have been extensively used for active vibration control of engineering structures. In this paper, piezoelectric materials further attempt to suppress the vibration of the aeroelastic wing caused by gust. The motion equation of the flexible wing with piezoelectric patches is obtained by Hamilton’s principle with the modal approach, and then numerical gust responses are analyzed, based on which a gust load alleviation (GLA control system is proposed. The gust load alleviation system employs classic proportional-integral-derivative (PID controllers which treat piezoelectric patches as control actuators and acceleration as the feedback signal. By a numerical method, the control mechanism that piezoelectric actuators can be used to alleviate gust-response loads is also analyzed qualitatively. Furthermore, through low-speed wind tunnel tests, the effectiveness of the gust load alleviation active control technology is validated. The test results agree well with the numerical results. Test results show that at a certain frequency range, the control scheme can effectively alleviate the z and x wingtip accelerations and the root bending moment of the wing to a certain extent. The control system gives satisfying gust load alleviation efficacy with the reduction rate being generally over 20%.
Chan, Cheng Leng; Rudrappa, Sowmya; Ang, Pei San; Li, Shu Chuen; Evans, Stephen J W
2017-08-01
The ability to detect safety concerns from spontaneous adverse drug reaction reports in a timely and efficient manner remains important in public health. This paper explores the behaviour of the Sequential Probability Ratio Test (SPRT) and ability to detect signals of disproportionate reporting (SDRs) in the Singapore context. We used SPRT with a combination of two hypothesised relative risks (hRRs) of 2 and 4.1 to detect signals of both common and rare adverse events in our small database. We compared SPRT with other methods in terms of number of signals detected and whether labelled adverse drug reactions were detected or the reaction terms were considered serious. The other methods used were reporting odds ratio (ROR), Bayesian Confidence Propagation Neural Network (BCPNN) and Gamma Poisson Shrinker (GPS). The SPRT produced 2187 signals in common with all methods, 268 unique signals, and 70 signals in common with at least one other method, and did not produce signals in 178 cases where two other methods detected them, and there were 403 signals unique to one of the other methods. In terms of sensitivity, ROR performed better than other methods, but the SPRT method found more new signals. The performances of the methods were similar for negative predictive value and specificity. Using a combination of hRRs for SPRT could be a useful screening tool for regulatory agencies, and more detailed investigation of the medical utility of the system is merited.
Proïa, Frédéric
2012-01-01
The purpose of this paper is to investigate the asymptotic behavior of the Durbin-Watson statistic for the general stable $p-$order autoregressive process when the driven noise is given by a first-order autoregressive process. We establish the almost sure convergence and the asymptotic normality for both the least squares estimator of the unknown vector parameter of the autoregressive process as well as for the serial correlation estimator associated with the driven noise. In addition, the almost sure rates of convergence of our estimates are also provided. Then, we prove the almost sure convergence and the asymptotic normality for the Durbin-Watson statistic. Finally, we propose a new bilateral statistical procedure for testing the presence of a significative first-order residual autocorrelation and we also explain how our procedure performs better than the commonly used Box-Pierce and Ljung-Box statistical tests for white noise applied to the stable autoregressive process, even on small-sized samples.
Walton, Karl; Fleming, Leigh; Goodhand, Martin; Racasan, Radu; Zeng, Wenhan
2016-06-01
This paper details, assesses and validates a technique for the replication of a titanium wind tunnel test aerofoil in polyurethane resin. Existing resin replication techniques are adapted to overcome the technical difficulties associated with casting a high aspect ratio component. The technique is shown to have high replication fidelity over all important length-scales. The blade chord was accurate to 0.02%, and the maximum blade thickness was accurate to 2.5%. Important spatial and amplitude areal surface texture parameter were accurate to within 2%. Compared to an existing similar system using correlation areal parameters the current technique is shown to have lower fidelity and this difference is discussed. The current technique was developed for the measurement of boundary layer flow ‘laminar to turbulent’ transition for gas turbine compressor blade profiles and this application is illustrated.
Løkkegaard, Thomas; Pedersen, Tina Heidi; Lind, Bent;
2015-01-01
INTRODUCTION: Oral anticoagulation treatment (OACT) with warfarin is common in general practice. Increasingly, international normalised ratio (INR) point of care testing (POCT) is being used to manage patients. The aim of this study was to describe and analyse the quality of OACT with warfarin...... in general practice in the Capital Region of Denmark using INR POCT. METHODS: A total of 20 general practices, ten single-handed and ten group practices using INR POCT, were randomly selected to participate in the study. Practice organisation and patient characteristics were recorded. INR measurements were...... collected retrospectively for a period of six months. For each patient, time in therapeutic range (TTR) was calculated and correlated with practice and patient characteristics using multilevel linear regression models. RESULTS: We identified 447 patients in warfarin treatment in the 20 practices using POCT...
Turle-Lorenzo, N; Zouani, B; Risso, J J
1999-09-01
Narcosis is a neurological syndrome that reduces capacities of divers. Although this phenomenon appeared at the end of 19th century, the mechanisms are not yet elucidated. The greatest technical problem is that these studies are carried out under hyperbaric conditions. Nitrous oxide is known to be an inducer of narcosis, at atmospheric pressure. The aim of this study is to compare two narcotic environments; a normobaric narcosis under several percentages of nitrous oxide, and an hyperbaric narcosis under 0.9 MPa of Nitrox (N2O2 mixture). This comparison is realized on rats submitted to a fixed-ratio 15 test, in which they have to press a lever to get rewarded. The results show significant performances decreases: the number of pressed lever are reduced by 50% under Nitrox and by 70% under N2O. Nitrous oxide could be considered as a normobaric model of hyperbaric narcosis.
Løkkegaard, Thomas; Pedersen, Tina Heidi; Lind, Bent;
2015-01-01
INTRODUCTION: Oral anticoagulation treatment (OACT)with warfarin is common in general practice. Increasingly,international normalised ratio (INR) point of care testing(POCT) is being used to manage patients. The aim of thisstudy was to describe and analyse the quality of OACT withwarfarin...... was notsignificant (4.2 percentage points (pp); 95% confidenceinterval (CI): –0.8-9.2). Short sampling intervals, e.g. 10-20days (–11 pp, 95% CI: –16-–6)) and lack of diagnostic coding(–11.8 pp; 95% CI: –19.9-–3.7) were correlated with a lowTTR. CONCLUSION: In our study most of the general practices usingINR POCT...... in the management of patients in warfarintreatment provided good quality of care. Sampling intervaland diagnostic coding were significantly correlated withtreatment quality. FUNDING: The study received financial support from theSarah Krabbe Foundation, the General Practitioners’ Educationand Development Foundation...
Dimitri, P. S.; Wall, C. 3rd; Oas, J. G.; Rauch, S. D.
2001-01-01
Meniere's disease (MD) and migraine associated dizziness (MAD) are two disorders that can have similar symptomatologies, but differ vastly in treatment. Vestibular testing is sometimes used to help differentiate between these disorders, but the inefficiency of a human interpreter analyzing a multitude of variables independently decreases its utility. Our hypothesis was that we could objectively discriminate between patients with MD and those with MAD using select variables from the vestibular test battery. Sinusoidal harmonic acceleration test variables were reduced to three vestibulo-ocular reflex physiologic parameters: gain, time constant, and asymmetry. A combination of these parameters plus a measurement of reduced vestibular response from caloric testing allowed us to achieve a joint classification rate of 91%, independent quadratic classification algorithm. Data from posturography were not useful for this type of differentiation. Overall, our classification function can be used as an unbiased assistant to discriminate between MD and MAD and gave us insight into the pathophysiologic differences between the two disorders.
Hughes, William O.; McNelis, Anne M.
2010-01-01
The Earth Observing System (EOS) Terra spacecraft was launched on an Atlas IIAS launch vehicle on its mission to observe planet Earth in late 1999. Prior to launch, the new design of the spacecraft's pyroshock separation system was characterized by a series of 13 separation ground tests. The analysis methods used to evaluate this unusually large amount of shock data will be discussed in this paper, with particular emphasis on population distributions and finding statistically significant families of data, leading to an overall shock separation interface level. The wealth of ground test data also allowed a derivation of a Mission Assurance level for the flight. All of the flight shock measurements were below the EOS Terra Mission Assurance level thus contributing to the overall success of the EOS Terra mission. The effectiveness of the statistical methodology for characterizing the shock interface level and for developing a flight Mission Assurance level from a large sample size of shock data is demonstrated in this paper.
Drop-Weight Impact Test on U-Shape Concrete Specimens with Statistical and Regression Analyses
Xue-Chao Zhu
2015-09-01
Full Text Available According to the principle and method of drop-weight impact test, the impact resistance of concrete was measured using self-designed U-shape specimens and a newly designed drop-weight impact test apparatus. A series of drop-weight impact tests were carried out with four different masses of drop hammers (0.875, 0.8, 0.675 and 0.5 kg. The test results show that the impact resistance results fail to follow a normal distribution. As expected, U-shaped specimens can predetermine the location of the cracks very well. It is also easy to record the cracks propagation during the test. The maximum of coefficient of variation in this study is 31.2%; it is lower than the values obtained from the American Concrete Institute (ACI impact tests in the literature. By regression analysis, the linear relationship between the first-crack and ultimate failure impact resistance is good. It can suggested that a minimum number of specimens is required to reliably measure the properties of the material based on the observed levels of variation.
Fujita, André; Takahashi, Daniel Y; Patriota, Alexandre G; Sato, João R
2014-12-10
Statistical inference of functional magnetic resonance imaging (fMRI) data is an important tool in neuroscience investigation. One major hypothesis in neuroscience is that the presence or not of a psychiatric disorder can be explained by the differences in how neurons cluster in the brain. Therefore, it is of interest to verify whether the properties of the clusters change between groups of patients and controls. The usual method to show group differences in brain imaging is to carry out a voxel-wise univariate analysis for a difference between the mean group responses using an appropriate test and to assemble the resulting 'significantly different voxels' into clusters, testing again at cluster level. In this approach, of course, the primary voxel-level test is blind to any cluster structure. Direct assessments of differences between groups at the cluster level seem to be missing in brain imaging. For this reason, we introduce a novel non-parametric statistical test called analysis of cluster structure variability (ANOCVA), which statistically tests whether two or more populations are equally clustered. The proposed method allows us to compare the clustering structure of multiple groups simultaneously and also to identify features that contribute to the differential clustering. We illustrate the performance of ANOCVA through simulations and an application to an fMRI dataset composed of children with attention deficit hyperactivity disorder (ADHD) and controls. Results show that there are several differences in the clustering structure of the brain between them. Furthermore, we identify some brain regions previously not described to be involved in the ADHD pathophysiology, generating new hypotheses to be tested. The proposed method is general enough to be applied to other types of datasets, not limited to fMRI, where comparison of clustering structures is of interest. Copyright © 2014 John Wiley & Sons, Ltd.
A Statistical Test of Walrasian Equilibrium by Means of Complex Networks Theory
Bargigli, Leonardo; Viaggiu, Stefano; Lionetto, Andrea
2016-09-01
We represent an exchange economy in terms of statistical ensembles for complex networks by introducing the concept of market configuration. This is defined as a sequence of nonnegative discrete random variables {w_{ij}} describing the flow of a given commodity from agent i to agent j. This sequence can be arranged in a nonnegative matrix W which we can regard as the representation of a weighted and directed network or digraph G. Our main result consists in showing that general equilibrium theory imposes highly restrictive conditions upon market configurations, which are in most cases not fulfilled by real markets. An explicit example with reference to the e-MID interbank credit market is provided.
A Statistical Test of Walrasian Equilibrium by Means of Complex Networks Theory
Bargigli, Leonardo; Viaggiu, Stefano; Lionetto, Andrea
2016-10-01
We represent an exchange economy in terms of statistical ensembles for complex networks by introducing the concept of market configuration. This is defined as a sequence of nonnegative discrete random variables {w_{ij}} describing the flow of a given commodity from agent i to agent j. This sequence can be arranged in a nonnegative matrix W which we can regard as the representation of a weighted and directed network or digraph G. Our main result consists in showing that general equilibrium theory imposes highly restrictive conditions upon market configurations, which are in most cases not fulfilled by real markets. An explicit example with reference to the e-MID interbank credit market is provided.
Berlin Sofia
2005-11-01
Full Text Available Abstract Background Adaptive evolution appears to be a common feature of reproductive proteins across a very wide range of organisms. A promising way of addressing the evolutionary forces responsible for this general phenomenon is to test for adaptive evolution in the same gene but among groups of species, which differ in their reproductive biology. One can then test evolutionary hypotheses by asking whether the variation in adaptive evolution is consistent with the variation in reproductive biology. We have attempted to apply this approach to the study of a female reproductive protein, zona pellucida C (ZPC, which has been previously shown by the use of likelihood ratio tests (LRTs to be under positive selection in mammals. Results We tested for evidence of adaptive evolution of ZPC in 15 mammalian species, in 11 avian species and in six fish species using three different LRTs (M1a-M2a, M7-M8, and M8a-M8. The only significant findings of adaptive evolution came from the M7-M8 test in mammals and fishes. Since LRTs of adaptive evolution may yield false positives in some situations, we examined the properties of the LRTs by several different simulation methods. When we simulated data to test the robustness of the LRTs, we found that the pattern of evolution in ZPC generates an excess of false positives for the M7-M8 LRT but not for the M1a-M2a or M8a-M8 LRTs. This bias is strong enough to have generated the significant M7-M8 results for mammals and fishes. Conclusion We conclude that there is no strong evidence for adaptive evolution of ZPC in any of the vertebrate groups we studied, and that the M7-M8 LRT can be biased towards false inference of adaptive evolution by certain patterns of non-adaptive evolution.
Voils, Stacy A; Martin, Erika J; Mohammed, Bassem M; Bayrlee, Ahmad; Brophy, Donald F
2015-06-01
We assess the in-vivo relationship between international normalized ratio (INR) and global coagulation tests in patients with life-threatening bleeding who received prothrombin complex concentrate (PCC) for warfarin reversal. This was a prospective pilot study in adult patients with intracranial bleeding related to anticoagulation with warfarin. Thromboelastography (TEG), thrombin generation parameters and INR were assessed at baseline, 30 min, 2 and 24 h after PCC. Changes in laboratory parameters and relationship between INR and global coagulation tests were assessed over time. Eight patients mean [standard deviation (SD)] age 72 (16) were included and received mean (SD) dose of PCC 24 (5) units/kg. Four patients died during the study, all with INR values more than 1.5 thirty minutes after PCC. Mean (SD) INR was 3.0 (1.3) and decreased significantly to 1.8 (0.48) thirty minutes after PCC (P administration. Reaction (R)-time decreased significantly (P = 0.02), and maximum amplitude and overall coagulation index (CI) significantly increased during treatment (P administration; however, INR did not fully correct. Patients that died tended to be older with prolonged INR values across the study period. INR and TEG values correlated well with thrombin generation before administration of PCC, but this relationship was lost afterward.
Amy-Klein, Anne; Lopez, Olivier; Daussy, Christophe; Kefelian, Fabien; Chardonnet, Christian [LPL, CNRS, Universite Paris-13, Villetaneuse (France); Shelkovnikov, Alexander [LPL, CNRS, Universite Paris-13, Villetaneuse (France); Lebedev Physical Institute, Moscow (Russian Federation); Butcher, Robert J. [LPL, CNRS, Universite Paris-13, Villetaneuse (France); Cavendish Laboratory, Cambridge (United Kingdom); Jiang, Haifeng; Santarelli, Giorgio [LNE-SYRTE, Observatoire de Paris, CNRS, UPMC (France)
2010-07-01
Time and frequency metrology has experienced a lot of developments since ten years leading to the possibility of many fundamental tests of physics, as, for example, the search for a temporal variation of fundamental constants. However these tests are limited to macroscopic resonators or atomic systems while molecular systems are still difficult to probe with a high sensitivity, since experiments on molecules lacks of absolute frequency measurements set-ups. In that context, we have developed an optical link between our lab and the LNE-SYRTE, which allows us to benefit from their frequency references. Using this link, we performed the first experimental comparison of a molecular clock to an atomic clock, which gives a direct line to the proton-to-electron mass ratio stability. Recently, we extended the frequency dissemination technique to non-dedicated fibers of the telecommunication network simultaneously carrying digital data from the Internet traffic. This is very challenging for the development of transcontinental atomic and molecular clocks comparisons.
The Probability of Exceedance as a Nonparametric Person-Fit Statistic for Tests of Moderate Length
Tendeiro, Jorge N.; Meijer, Rob R.
2013-01-01
To classify an item score pattern as not fitting a nonparametric item response theory (NIRT) model, the probability of exceedance (PE) of an observed response vector x can be determined as the sum of the probabilities of all response vectors that are, at most, as likely as x, conditional on the test
Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity
Beasley, T. Mark
2014-01-01
Increasing the correlation between the independent variable and the mediator ("a" coefficient) increases the effect size ("ab") for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation caused by…
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…
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...
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.
Relationship between the COI test and other sensory profiles by statistical procedures
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.
An improved classification of foci for carcinogenicity testing by statistical descriptors.
Callegaro, Giulia; Stefanini, Federico Mattia; Colacci, Annamaria; Vaccari, Monica; Urani, Chiara
2015-10-01
Carcinogenesis is a multi-step process involving genetic alterations and non-genotoxic mechanisms. The in vitro cell transformation assay (CTA) is a promising tool for both genotoxic and non-genotoxic carcinogenesis. CTA relies on the ability of cells (e.g. BALB/c 3T3 mouse embryo fibroblasts) to develop a transformed phenotype after the treatment with suspected carcinogens. The classification of the transformed phenotype is based on coded morphological features, which are scored under a light microscope by trained experts. This procedure is time-consuming and somewhat prone to subjectivity. Herewith we provide a promising approach based on image analysis to support the scoring of malignant foci in BALB/c 3T3 CTA. The image analysis system is a quantitative approach, based on measuring features of malignant foci: dimension, multilayered growth, and invasivity into the surrounding monolayer of non-transformed cells. A logistic regression model was developed to estimate the probability for each focus to be transformed as a function of three statistical image descriptors. The estimated sensitivity of the derived classifier (untransformed against Type III) was 0.9, with an Area Under the Curve (AUC) value equal to 0.90 under the Receiver Operating Characteristics (ROC) curve.
EEG-based Drowsiness Detection for Safe Driving Using Chaotic Features and Statistical Tests
Mardi, Zahra; Ashtiani, Seyedeh Naghmeh Miri; Mikaili, Mohammad
2011-01-01
Electro encephalography (EEG) is one of the most reliable sources to detect sleep onset while driving. In this study, we have tried to demonstrate that sleepiness and alertness signals are separable with an appropriate margin by extracting suitable features. So, first of all, we have recorded EEG signals from 10 volunteers. They were obliged to avoid sleeping for about 20 hours before the test. We recorded the signals while subjects did a virtual driving game. They tried to pass some barriers...
Pater, Liana; Miclea, Şerban; Izvercian, Monica
2016-06-01
This paper considers the impact of SMEs' annual turnover upon its marketing activities (in terms of marketing responsibility, strategic planning and budgeting). Empirical results and literature reviews unveil that SMEs managers incline to partake in planned and profitable marketing activities, depending on their turnover's level. Thus, using the collected data form 131 Romanian SMEs managers, we have applied the Chi-Square Test in order to validate or invalidate three research assumptions (hypotheses), created starting from the empirical and literature findings.
Statistical test for detecting community structure in real-valued edge-weighted graphs
Tokuda, Tomoki
2016-01-01
We propose a novel method to test the existence of community structure of undirected real-valued edge-weighted graph. The method is based on Wigner semicircular law on the asymptotic behavior of the random distribution for eigenvalues of a real symmetric matrix. We provide a theoretical foundation for this method and report on its performance in synthetic and real data, suggesting that our method outperforms other state-of-the-art methods.
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.
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.
Adams, Michael C; Barbano, David M
2015-06-01
Our objective was to develop a statistical approach that could be used to determine whether a handler's fat, protein, or other solids mid-infrared (MIR) spectrophotometer test values were different, on average, from a milk regulatory laboratory's MIR test values when split-sampling test values are not available. To accomplish this objective, the Proc GLM procedure of SAS (SAS Institute Inc., Cary, NC) was used to develop a multiple linear regression model to evaluate 4 mo of MIR producer payment testing data (112 to 167 producers per month) from 2 different MIR instruments. For each of the 4 mo and each of the 2 components (fat or protein), the GLM model was Response=Instrument+Producer+Date+2-Way Interactions+3-Way Interaction. Instrument was significant in determining fat and protein tests for 3 of the 4 mo, and Producer was significant in determining fat and protein tests for all 4 mo. This model was also used to establish fat and protein least significant differences (LSD) between instruments. Fat LSD between instruments ranged from 0.0108 to 0.0144% (α=0.05) for the 4 mo studied, whereas protein LSD between instruments ranged from 0.0046 to 0.0085% (α=0.05). In addition, regression analysis was used to determine the effects of component concentration and date of sampling on fat and protein differences between 2 MIR instruments. This statistical approach could be performed monthly to document a regulatory laboratory's verification that a given handler's instrument has obtained a different test result, on average, from that of the regulatory laboratory's and that an adjustment to producer payment may be required.