THE FLUORBOARD A STATISTICALLY BASED DASHBOARD METHOD FOR IMPROVING SAFETY

International Nuclear Information System (INIS)

PREVETTE, S.S.

2005-01-01

The FluorBoard is a statistically based dashboard method for improving safety. Fluor Hanford has achieved significant safety improvements--including more than a 80% reduction in OSHA cases per 200,000 hours, during its work at the US Department of Energy's Hanford Site in Washington state. The massive project on the former nuclear materials production site is considered one of the largest environmental cleanup projects in the world. Fluor Hanford's safety improvements were achieved by a committed partnering of workers, managers, and statistical methodology. Safety achievements at the site have been due to a systematic approach to safety. This includes excellent cooperation between the field workers, the safety professionals, and management through OSHA Voluntary Protection Program principles. Fluor corporate values are centered around safety, and safety excellence is important for every manager in every project. In addition, Fluor Hanford has utilized a rigorous approach to using its safety statistics, based upon Dr. Shewhart's control charts, and Dr. Deming's management and quality methods

Static quarks with improved statistical precision

International Nuclear Information System (INIS)

Della Morte, M.; Duerr, S.; Molke, H.; Heitger, J.

2003-09-01

We present a numerical study for different discretisations of the static action, concerning cut-off effects and the growth of statistical errors with Euclidean time. An error reduction by an order of magnitude can be obtained with respect to the Eichten-Hill action, for time separations up to 2 fm, keeping discretization errors small. The best actions lead to a big improvement on the precision of the quark mass M b and F B s in the static approximation. (orig.)

Linnorm: improved statistical analysis for single cell RNA-seq expression data.

Science.gov (United States)

Yip, Shun H; Wang, Panwen; Kocher, Jean-Pierre A; Sham, Pak Chung; Wang, Junwen

2017-12-15

Linnorm is a novel normalization and transformation method for the analysis of single cell RNA sequencing (scRNA-seq) data. Linnorm is developed to remove technical noises and simultaneously preserve biological variations in scRNA-seq data, such that existing statistical methods can be improved. Using real scRNA-seq data, we compared Linnorm with existing normalization methods, including NODES, SAMstrt, SCnorm, scran, DESeq and TMM. Linnorm shows advantages in speed, technical noise removal and preservation of cell heterogeneity, which can improve existing methods in the discovery of novel subtypes, pseudo-temporal ordering of cells, clustering analysis, etc. Linnorm also performs better than existing DEG analysis methods, including BASiCS, NODES, SAMstrt, Seurat and DESeq2, in false positive rate control and accuracy. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Statistics Education Research in Malaysia and the Philippines: A Comparative Analysis

Science.gov (United States)

Reston, Enriqueta; Krishnan, Saras; Idris, Noraini

2014-01-01

This paper presents a comparative analysis of statistics education research in Malaysia and the Philippines by modes of dissemination, research areas, and trends. An electronic search for published research papers in the area of statistics education from 2000-2012 yielded 20 for Malaysia and 19 for the Philippines. Analysis of these papers showed…

Statistical and Machine-Learning Classifier Framework to Improve Pulse Shape Discrimination System Design

Energy Technology Data Exchange (ETDEWEB)

Wurtz, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kaplan, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-10-28

Pulse shape discrimination (PSD) is a variety of statistical classifier. Fully-­realized statistical classifiers rely on a comprehensive set of tools for designing, building, and implementing. PSD advances rely on improvements to the implemented algorithm. PSD advances can be improved by using conventional statistical classifier or machine learning methods. This paper provides the reader with a glossary of classifier-­building elements and their functions in a fully-­designed and operational classifier framework that can be used to discover opportunities for improving PSD classifier projects. This paper recommends reporting the PSD classifier’s receiver operating characteristic (ROC) curve and its behavior at a gamma rejection rate (GRR) relevant for realistic applications.

[More than a decade improving medical and judicial certification in mortality statistics of death causes].

Science.gov (United States)

Cirera, Lluís; Salmerón, Diego; Martínez, Consuelo; Bañón, Rafael María; Navarro, Carmen

2018-06-06

After the return of Spain to democracy and the regional assumption of government powers, actions were initiated to improve the mortality statistics of death causes. The objective of this work was to describe the evolution of the quality activities improvements into the statistics of death causes on Murcia's region during 1989 to 2011. Descriptive epidemiological study of all death documents processed by the Murcia mortality registry. Use of indicators related to the quality of the completion of death in medical and judicial notification; recovery of information on the causes and circumstances of death; and impact on the statistics of ill-defined, unspecific and less specific causes. During the study period, the medical notification without a temporary sequence on the death certificate (DC) has decreased from 46% initial to 21% final (p less than 0.001). Information retrieval from sources was successful in 93% of the cases in 2001 compared to 38%, at the beginning of the period (p less than 0.001). Regional rates of ill-defined and unspecific causes fell more than national ones, and they were in the last year with a differential of 10.3 (p less than 0.001) and 2.8 points (p=0.001), respectively. The medical death certification improved in form and suitability. Regulated recovery of the causes of death and circumstances corrected medical and judicial information. The Murcia's region presented lower rates in less specified causes and ill-defined entities than national averages.

Introduction of a Journal Excerpt Activity Improves Undergraduate Students' Performance in Statistics

Science.gov (United States)

Rabin, Laura A.; Nutter-Upham, Katherine E.

2010-01-01

We describe an active learning exercise intended to improve undergraduate students' understanding of statistics by grounding complex concepts within a meaningful, applied context. Students in a journal excerpt activity class read brief excerpts of statistical reporting from published research articles, answered factual and interpretive questions,…

Reaming process improvement and control: An application of statistical engineering

DEFF Research Database (Denmark)

Müller, Pavel; Genta, G.; Barbato, G.

2012-01-01

A reaming operation had to be performed within given technological and economical constraints. Process improvement under realistic conditions was the goal of a statistical engineering project, supported by a comprehensive experimental investigation providing detailed information on single...

Statistical process control methods allow the analysis and improvement of anesthesia care.

Science.gov (United States)

Fasting, Sigurd; Gisvold, Sven E

2003-10-01

Quality aspects of the anesthetic process are reflected in the rate of intraoperative adverse events. The purpose of this report is to illustrate how the quality of the anesthesia process can be analyzed using statistical process control methods, and exemplify how this analysis can be used for quality improvement. We prospectively recorded anesthesia-related data from all anesthetics for five years. The data included intraoperative adverse events, which were graded into four levels, according to severity. We selected four adverse events, representing important quality and safety aspects, for statistical process control analysis. These were: inadequate regional anesthesia, difficult emergence from general anesthesia, intubation difficulties and drug errors. We analyzed the underlying process using 'p-charts' for statistical process control. In 65,170 anesthetics we recorded adverse events in 18.3%; mostly of lesser severity. Control charts were used to define statistically the predictable normal variation in problem rate, and then used as a basis for analysis of the selected problems with the following results: Inadequate plexus anesthesia: stable process, but unacceptably high failure rate; Difficult emergence: unstable process, because of quality improvement efforts; Intubation difficulties: stable process, rate acceptable; Medication errors: methodology not suited because of low rate of errors. By applying statistical process control methods to the analysis of adverse events, we have exemplified how this allows us to determine if a process is stable, whether an intervention is required, and if quality improvement efforts have the desired effect.

Comparing Data Sets: Implicit Summaries of the Statistical Properties of Number Sets

Science.gov (United States)

Morris, Bradley J.; Masnick, Amy M.

2015-01-01

Comparing datasets, that is, sets of numbers in context, is a critical skill in higher order cognition. Although much is known about how people compare single numbers, little is known about how number sets are represented and compared. We investigated how subjects compared datasets that varied in their statistical properties, including ratio of…

Statistical reviewers improve reporting in biomedical articles: a randomized trial.

Directory of Open Access Journals (Sweden)

Erik Cobo

2007-03-01

Full Text Available Although peer review is widely considered to be the most credible way of selecting manuscripts and improving the quality of accepted papers in scientific journals, there is little evidence to support its use. Our aim was to estimate the effects on manuscript quality of either adding a statistical peer reviewer or suggesting the use of checklists such as CONSORT or STARD to clinical reviewers or both.Interventions were defined as 1 the addition of a statistical reviewer to the clinical peer review process, and 2 suggesting reporting guidelines to reviewers; with "no statistical expert" and "no checklist" as controls. The two interventions were crossed in a 2x2 balanced factorial design including original research articles consecutively selected, between May 2004 and March 2005, by the Medicina Clinica (Barc editorial committee. We randomized manuscripts to minimize differences in terms of baseline quality and type of study (intervention, longitudinal, cross-sectional, others. Sample-size calculations indicated that 100 papers provide an 80% power to test a 55% standardized difference. We specified the main outcome as the increment in quality of papers as measured on the Goodman Scale. Two blinded evaluators rated the quality of manuscripts at initial submission and final post peer review version. Of the 327 manuscripts submitted to the journal, 131 were accepted for further review, and 129 were randomized. Of those, 14 that were lost to follow-up showed no differences in initial quality to the followed-up papers. Hence, 115 were included in the main analysis, with 16 rejected for publication after peer review. 21 (18.3% of the 115 included papers were interventions, 46 (40.0% were longitudinal designs, 28 (24.3% cross-sectional and 20 (17.4% others. The 16 (13.9% rejected papers had a significantly lower initial score on the overall Goodman scale than accepted papers (difference 15.0, 95% CI: 4.6-24.4. The effect of suggesting a guideline to the

Content-based VLE designs improve learning efficiency in constructivist statistics education.

Science.gov (United States)

Wessa, Patrick; De Rycker, Antoon; Holliday, Ian Edward

2011-01-01

We introduced a series of computer-supported workshops in our undergraduate statistics courses, in the hope that it would help students to gain a deeper understanding of statistical concepts. This raised questions about the appropriate design of the Virtual Learning Environment (VLE) in which such an approach had to be implemented. Therefore, we investigated two competing software design models for VLEs. In the first system, all learning features were a function of the classical VLE. The second system was designed from the perspective that learning features should be a function of the course's core content (statistical analyses), which required us to develop a specific-purpose Statistical Learning Environment (SLE) based on Reproducible Computing and newly developed Peer Review (PR) technology. The main research question is whether the second VLE design improved learning efficiency as compared to the standard type of VLE design that is commonly used in education. As a secondary objective we provide empirical evidence about the usefulness of PR as a constructivist learning activity which supports non-rote learning. Finally, this paper illustrates that it is possible to introduce a constructivist learning approach in large student populations, based on adequately designed educational technology, without subsuming educational content to technological convenience. Both VLE systems were tested within a two-year quasi-experiment based on a Reliable Nonequivalent Group Design. This approach allowed us to draw valid conclusions about the treatment effect of the changed VLE design, even though the systems were implemented in successive years. The methodological aspects about the experiment's internal validity are explained extensively. The effect of the design change is shown to have substantially increased the efficiency of constructivist, computer-assisted learning activities for all cohorts of the student population under investigation. The findings demonstrate that a

Content-based VLE designs improve learning efficiency in constructivist statistics education.

Directory of Open Access Journals (Sweden)

Patrick Wessa

Full Text Available BACKGROUND: We introduced a series of computer-supported workshops in our undergraduate statistics courses, in the hope that it would help students to gain a deeper understanding of statistical concepts. This raised questions about the appropriate design of the Virtual Learning Environment (VLE in which such an approach had to be implemented. Therefore, we investigated two competing software design models for VLEs. In the first system, all learning features were a function of the classical VLE. The second system was designed from the perspective that learning features should be a function of the course's core content (statistical analyses, which required us to develop a specific-purpose Statistical Learning Environment (SLE based on Reproducible Computing and newly developed Peer Review (PR technology. OBJECTIVES: The main research question is whether the second VLE design improved learning efficiency as compared to the standard type of VLE design that is commonly used in education. As a secondary objective we provide empirical evidence about the usefulness of PR as a constructivist learning activity which supports non-rote learning. Finally, this paper illustrates that it is possible to introduce a constructivist learning approach in large student populations, based on adequately designed educational technology, without subsuming educational content to technological convenience. METHODS: Both VLE systems were tested within a two-year quasi-experiment based on a Reliable Nonequivalent Group Design. This approach allowed us to draw valid conclusions about the treatment effect of the changed VLE design, even though the systems were implemented in successive years. The methodological aspects about the experiment's internal validity are explained extensively. RESULTS: The effect of the design change is shown to have substantially increased the efficiency of constructivist, computer-assisted learning activities for all cohorts of the student

Content-Based VLE Designs Improve Learning Efficiency in Constructivist Statistics Education

Science.gov (United States)

Wessa, Patrick; De Rycker, Antoon; Holliday, Ian Edward

2011-01-01

Background We introduced a series of computer-supported workshops in our undergraduate statistics courses, in the hope that it would help students to gain a deeper understanding of statistical concepts. This raised questions about the appropriate design of the Virtual Learning Environment (VLE) in which such an approach had to be implemented. Therefore, we investigated two competing software design models for VLEs. In the first system, all learning features were a function of the classical VLE. The second system was designed from the perspective that learning features should be a function of the course's core content (statistical analyses), which required us to develop a specific–purpose Statistical Learning Environment (SLE) based on Reproducible Computing and newly developed Peer Review (PR) technology. Objectives The main research question is whether the second VLE design improved learning efficiency as compared to the standard type of VLE design that is commonly used in education. As a secondary objective we provide empirical evidence about the usefulness of PR as a constructivist learning activity which supports non-rote learning. Finally, this paper illustrates that it is possible to introduce a constructivist learning approach in large student populations, based on adequately designed educational technology, without subsuming educational content to technological convenience. Methods Both VLE systems were tested within a two-year quasi-experiment based on a Reliable Nonequivalent Group Design. This approach allowed us to draw valid conclusions about the treatment effect of the changed VLE design, even though the systems were implemented in successive years. The methodological aspects about the experiment's internal validity are explained extensively. Results The effect of the design change is shown to have substantially increased the efficiency of constructivist, computer-assisted learning activities for all cohorts of the student population under

Statistical analysis of textural features for improved classification of oral histopathological images.

Science.gov (United States)

Muthu Rama Krishnan, M; Shah, Pratik; Chakraborty, Chandan; Ray, Ajoy K

2012-04-01

The objective of this paper is to provide an improved technique, which can assist oncopathologists in correct screening of oral precancerous conditions specially oral submucous fibrosis (OSF) with significant accuracy on the basis of collagen fibres in the sub-epithelial connective tissue. The proposed scheme is composed of collagen fibres segmentation, its textural feature extraction and selection, screening perfomance enhancement under Gaussian transformation and finally classification. In this study, collagen fibres are segmented on R,G,B color channels using back-probagation neural network from 60 normal and 59 OSF histological images followed by histogram specification for reducing the stain intensity variation. Henceforth, textural features of collgen area are extracted using fractal approaches viz., differential box counting and brownian motion curve . Feature selection is done using Kullback-Leibler (KL) divergence criterion and the screening performance is evaluated based on various statistical tests to conform Gaussian nature. Here, the screening performance is enhanced under Gaussian transformation of the non-Gaussian features using hybrid distribution. Moreover, the routine screening is designed based on two statistical classifiers viz., Bayesian classification and support vector machines (SVM) to classify normal and OSF. It is observed that SVM with linear kernel function provides better classification accuracy (91.64%) as compared to Bayesian classifier. The addition of fractal features of collagen under Gaussian transformation improves Bayesian classifier's performance from 80.69% to 90.75%. Results are here studied and discussed.

Retention of Statistical Concepts in a Preliminary Randomization-Based Introductory Statistics Curriculum

Science.gov (United States)

Tintle, Nathan; Topliff, Kylie; VanderStoep, Jill; Holmes, Vicki-Lynn; Swanson, Todd

2012-01-01

Previous research suggests that a randomization-based introductory statistics course may improve student learning compared to the consensus curriculum. However, it is unclear whether these gains are retained by students post-course. We compared the conceptual understanding of a cohort of students who took a randomization-based curriculum (n = 76)…

Statistical methods of evaluating and comparing imaging techniques

International Nuclear Information System (INIS)

Freedman, L.S.

1987-01-01

Over the past 20 years several new methods of generating images of internal organs and the anatomy of the body have been developed and used to enhance the accuracy of diagnosis and treatment. These include ultrasonic scanning, radioisotope scanning, computerised X-ray tomography (CT) and magnetic resonance imaging (MRI). The new techniques have made a considerable impact on radiological practice in hospital departments, not least on the investigational process for patients suspected or known to have malignant disease. As a consequence of the increased range of imaging techniques now available, there has developed a need to evaluate and compare their usefulness. Over the past 10 years formal studies of the application of imaging technology have been conducted and many reports have appeared in the literature. These studies cover a range of clinical situations. Likewise, the methodologies employed for evaluating and comparing the techniques in question have differed widely. While not attempting an exhaustive review of the clinical studies which have been reported, this paper aims to examine the statistical designs and analyses which have been used. First a brief review of the different types of study is given. Examples of each type are then chosen to illustrate statistical issues related to their design and analysis. In the final sections it is argued that a form of classification for these different types of study might be helpful in clarifying relationships between them and bringing a perspective to the field. A classification based upon a limited analogy with clinical trials is suggested

Fundamentals of modern statistical methods substantially improving power and accuracy

CERN Document Server

Wilcox, Rand R

2001-01-01

Conventional statistical methods have a very serious flaw They routinely miss differences among groups or associations among variables that are detected by more modern techniques - even under very small departures from normality Hundreds of journal articles have described the reasons standard techniques can be unsatisfactory, but simple, intuitive explanations are generally unavailable Improved methods have been derived, but they are far from obvious or intuitive based on the training most researchers receive Situations arise where even highly nonsignificant results become significant when analyzed with more modern methods Without assuming any prior training in statistics, Part I of this book describes basic statistical principles from a point of view that makes their shortcomings intuitive and easy to understand The emphasis is on verbal and graphical descriptions of concepts Part II describes modern methods that address the problems covered in Part I Using data from actual studies, many examples are include...

Improving esthetic results in benign parotid surgery: statistical evaluation of facelift approach, sternocleidomastoid flap, and superficial musculoaponeurotic system flap application.

Science.gov (United States)

Bianchi, Bernardo; Ferri, Andrea; Ferrari, Silvano; Copelli, Chiara; Sesenna, Enrico

2011-04-01

The purpose of this article was to analyze the efficacy of facelift incision, sternocleidomastoid muscle flap, and superficial musculoaponeurotic system flap for improving the esthetic results in patients undergoing partial parotidectomy for benign parotid tumor resection. The usefulness of partial parotidectomy is discussed, and a statistical evaluation of the esthetic results was performed. From January 1, 1996, to January 1, 2007, 274 patients treated for benign parotid tumors were studied. Of these, 172 underwent partial parotidectomy. The 172 patients were divided into 4 groups: partial parotidectomy with classic or modified Blair incision without reconstruction (group 1), partial parotidectomy with facelift incision and without reconstruction (group 2), partial parotidectomy with facelift incision associated with sternocleidomastoid muscle flap (group 3), and partial parotidectomy with facelift incision associated with superficial musculoaponeurotic system flap (group 4). Patients were considered, after a follow-up of at least 18 months, for functional and esthetic evaluation. The functional outcome was assessed considering the facial nerve function, Frey syndrome, and recurrence. The esthetic evaluation was performed by inviting the patients and a blind panel of 1 surgeon and 2 secretaries of the department to give a score of 1 to 10 to assess the final cosmetic outcome. The statistical analysis was finally performed using the Mann-Whitney U test for nonparametric data to compare the different group results. P less than .05 was considered significant. No recurrence developed in any of the 4 groups or in any of the 274 patients during the follow-up period. The statistical analysis, comparing group 1 and the other groups, revealed a highly significant statistical difference (P esthetic results in benign parotid surgery. The evaluation of functional complications and the recurrence rate in this series of patients has confirmed that this technique can be safely

Improving UWB-Based Localization in IoT Scenarios with Statistical Models of Distance Error.

Science.gov (United States)

Monica, Stefania; Ferrari, Gianluigi

2018-05-17

Interest in the Internet of Things (IoT) is rapidly increasing, as the number of connected devices is exponentially growing. One of the application scenarios envisaged for IoT technologies involves indoor localization and context awareness. In this paper, we focus on a localization approach that relies on a particular type of communication technology, namely Ultra Wide Band (UWB). UWB technology is an attractive choice for indoor localization, owing to its high accuracy. Since localization algorithms typically rely on estimated inter-node distances, the goal of this paper is to evaluate the improvement brought by a simple (linear) statistical model of the distance error. On the basis of an extensive experimental measurement campaign, we propose a general analytical framework, based on a Least Square (LS) method, to derive a novel statistical model for the range estimation error between a pair of UWB nodes. The proposed statistical model is then applied to improve the performance of a few illustrative localization algorithms in various realistic scenarios. The obtained experimental results show that the use of the proposed statistical model improves the accuracy of the considered localization algorithms with a reduction of the localization error up to 66%.

A Quantitative Comparative Study of Blended and Traditional Models in the Secondary Advanced Placement Statistics Classroom

Science.gov (United States)

Owens, Susan T.

2017-01-01

Technology is becoming an integral tool in the classroom and can make a positive impact on how the students learn. This quantitative comparative research study examined gender-based differences among secondary Advanced Placement (AP) Statistic students comparing Educational Testing Service (ETS) College Board AP Statistic examination scores…

Advanced statistics to improve the physical interpretation of atomization processes

International Nuclear Information System (INIS)

Panão, Miguel R.O.; Radu, Lucian

2013-01-01

Highlights: ► Finite pdf mixtures improves physical interpretation of sprays. ► Bayesian approach using MCMC algorithm is used to find the best finite mixture. ► Statistical method identifies multiple droplet clusters in a spray. ► Multiple drop clusters eventually associated with multiple atomization mechanisms. ► Spray described by drop size distribution and not only its moments. -- Abstract: This paper reports an analysis of the physics of atomization processes using advanced statistical tools. Namely, finite mixtures of probability density functions, which best fitting is found using a Bayesian approach based on a Markov chain Monte Carlo (MCMC) algorithm. This approach takes into account eventual multimodality and heterogeneities in drop size distributions. Therefore, it provides information about the complete probability density function of multimodal drop size distributions and allows the identification of subgroups in the heterogeneous data. This allows improving the physical interpretation of atomization processes. Moreover, it also overcomes the limitations induced by analyzing the spray droplets characteristics through moments alone, particularly, the hindering of different natures of droplet formation. Finally, the method is applied to physically interpret a case-study based on multijet atomization processes

Statistical methods for quality assurance basics, measurement, control, capability, and improvement

CERN Document Server

Vardeman, Stephen B

2016-01-01

This undergraduate statistical quality assurance textbook clearly shows with real projects, cases and data sets how statistical quality control tools are used in practice. Among the topics covered is a practical evaluation of measurement effectiveness for both continuous and discrete data. Gauge Reproducibility and Repeatability methodology (including confidence intervals for Repeatability, Reproducibility and the Gauge Capability Ratio) is thoroughly developed. Process capability indices and corresponding confidence intervals are also explained. In addition to process monitoring techniques, experimental design and analysis for process improvement are carefully presented. Factorial and Fractional Factorial arrangements of treatments and Response Surface methods are covered. Integrated throughout the book are rich sets of examples and problems that help readers gain a better understanding of where and how to apply statistical quality control tools. These large and realistic problem sets in combination with the...

Comparative analysis of positive and negative attitudes toward statistics

Science.gov (United States)

Ghulami, Hassan Rahnaward; Ab Hamid, Mohd Rashid; Zakaria, Roslinazairimah

2015-02-01

Many statistics lecturers and statistics education researchers are interested to know the perception of their students' attitudes toward statistics during the statistics course. In statistics course, positive attitude toward statistics is a vital because it will be encourage students to get interested in the statistics course and in order to master the core content of the subject matters under study. Although, students who have negative attitudes toward statistics they will feel depressed especially in the given group assignment, at risk for failure, are often highly emotional, and could not move forward. Therefore, this study investigates the students' attitude towards learning statistics. Six latent constructs have been the measurement of students' attitudes toward learning statistic such as affect, cognitive competence, value, difficulty, interest, and effort. The questionnaire was adopted and adapted from the reliable and validate instrument of Survey of Attitudes towards Statistics (SATS). This study is conducted among engineering undergraduate engineering students in the university Malaysia Pahang (UMP). The respondents consist of students who were taking the applied statistics course from different faculties. From the analysis, it is found that the questionnaire is acceptable and the relationships among the constructs has been proposed and investigated. In this case, students show full effort to master the statistics course, feel statistics course enjoyable, have confidence that they have intellectual capacity, and they have more positive attitudes then negative attitudes towards statistics learning. In conclusion in terms of affect, cognitive competence, value, interest and effort construct the positive attitude towards statistics was mostly exhibited. While negative attitudes mostly exhibited by difficulty construct.

Statistical iterative reconstruction to improve image quality for digital breast tomosynthesis

International Nuclear Information System (INIS)

Xu, Shiyu; Chen, Ying; Lu, Jianping; Zhou, Otto

2015-01-01

Purpose: Digital breast tomosynthesis (DBT) is a novel modality with the potential to improve early detection of breast cancer by providing three-dimensional (3D) imaging with a low radiation dose. 3D image reconstruction presents some challenges: cone-beam and flat-panel geometry, and highly incomplete sampling. A promising means to overcome these challenges is statistical iterative reconstruction (IR), since it provides the flexibility of accurate physics modeling and a general description of system geometry. The authors’ goal was to develop techniques for applying statistical IR to tomosynthesis imaging data. Methods: These techniques include the following: a physics model with a local voxel-pair based prior with flexible parameters to fine-tune image quality; a precomputed parameter λ in the prior, to remove data dependence and to achieve a uniform resolution property; an effective ray-driven technique to compute the forward and backprojection; and an oversampled, ray-driven method to perform high resolution reconstruction with a practical region-of-interest technique. To assess the performance of these techniques, the authors acquired phantom data on the stationary DBT prototype system. To solve the estimation problem, the authors proposed an optimization-transfer based algorithm framework that potentially allows fewer iterations to achieve an acceptably converged reconstruction. Results: IR improved the detectability of low-contrast and small microcalcifications, reduced cross-plane artifacts, improved spatial resolution, and lowered noise in reconstructed images. Conclusions: Although the computational load remains a significant challenge for practical development, the superior image quality provided by statistical IR, combined with advancing computational techniques, may bring benefits to screening, diagnostics, and intraoperative imaging in clinical applications

Statistical iterative reconstruction to improve image quality for digital breast tomosynthesis

Energy Technology Data Exchange (ETDEWEB)

Xu, Shiyu, E-mail: shiyu.xu@gmail.com; Chen, Ying, E-mail: adachen@siu.edu [Department of Electrical and Computer Engineering, Southern Illinois University Carbondale, Carbondale, Illinois 62901 (United States); Lu, Jianping; Zhou, Otto [Department of Physics and Astronomy and Curriculum in Applied Sciences and Engineering, University of North Carolina Chapel Hill, Chapel Hill, North Carolina 27599 (United States)

2015-09-15

Purpose: Digital breast tomosynthesis (DBT) is a novel modality with the potential to improve early detection of breast cancer by providing three-dimensional (3D) imaging with a low radiation dose. 3D image reconstruction presents some challenges: cone-beam and flat-panel geometry, and highly incomplete sampling. A promising means to overcome these challenges is statistical iterative reconstruction (IR), since it provides the flexibility of accurate physics modeling and a general description of system geometry. The authors’ goal was to develop techniques for applying statistical IR to tomosynthesis imaging data. Methods: These techniques include the following: a physics model with a local voxel-pair based prior with flexible parameters to fine-tune image quality; a precomputed parameter λ in the prior, to remove data dependence and to achieve a uniform resolution property; an effective ray-driven technique to compute the forward and backprojection; and an oversampled, ray-driven method to perform high resolution reconstruction with a practical region-of-interest technique. To assess the performance of these techniques, the authors acquired phantom data on the stationary DBT prototype system. To solve the estimation problem, the authors proposed an optimization-transfer based algorithm framework that potentially allows fewer iterations to achieve an acceptably converged reconstruction. Results: IR improved the detectability of low-contrast and small microcalcifications, reduced cross-plane artifacts, improved spatial resolution, and lowered noise in reconstructed images. Conclusions: Although the computational load remains a significant challenge for practical development, the superior image quality provided by statistical IR, combined with advancing computational techniques, may bring benefits to screening, diagnostics, and intraoperative imaging in clinical applications.

Toward Global Comparability of Sexual Orientation Data in Official Statistics: A Conceptual Framework of Sexual Orientation for Health Data Collection in New Zealand's Official Statistics System

Science.gov (United States)

Gray, Alistair; Veale, Jaimie F.; Binson, Diane; Sell, Randell L.

2013-01-01

Objective. Effectively addressing health disparities experienced by sexual minority populations requires high-quality official data on sexual orientation. We developed a conceptual framework of sexual orientation to improve the quality of sexual orientation data in New Zealand's Official Statistics System. Methods. We reviewed conceptual and methodological literature, culminating in a draft framework. To improve the framework, we held focus groups and key-informant interviews with sexual minority stakeholders and producers and consumers of official statistics. An advisory board of experts provided additional guidance. Results. The framework proposes working definitions of the sexual orientation topic and measurement concepts, describes dimensions of the measurement concepts, discusses variables framing the measurement concepts, and outlines conceptual grey areas. Conclusion. The framework proposes standard definitions and concepts for the collection of official sexual orientation data in New Zealand. It presents a model for producers of official statistics in other countries, who wish to improve the quality of health data on their citizens. PMID:23840231

Comparing geological and statistical approaches for element selection in sediment tracing research

Science.gov (United States)

Laceby, J. Patrick; McMahon, Joe; Evrard, Olivier; Olley, Jon

2015-04-01

Elevated suspended sediment loads reduce reservoir capacity and significantly increase the cost of operating water treatment infrastructure, making the management of sediment supply to reservoirs of increasingly importance. Sediment fingerprinting techniques can be used to determine the relative contributions of different sources of sediment accumulating in reservoirs. The objective of this research is to compare geological and statistical approaches to element selection for sediment fingerprinting modelling. Time-integrated samplers (n=45) were used to obtain source samples from four major subcatchments flowing into the Baroon Pocket Dam in South East Queensland, Australia. The geochemistry of potential sources were compared to the geochemistry of sediment cores (n=12) sampled in the reservoir. The geochemical approach selected elements for modelling that provided expected, observed and statistical discrimination between sediment sources. Two statistical approaches selected elements for modelling with the Kruskal-Wallis H-test and Discriminatory Function Analysis (DFA). In particular, two different significance levels (0.05 & 0.35) for the DFA were included to investigate the importance of element selection on modelling results. A distribution model determined the relative contributions of different sources to sediment sampled in the Baroon Pocket Dam. Elemental discrimination was expected between one subcatchment (Obi Obi Creek) and the remaining subcatchments (Lexys, Falls and Bridge Creek). Six major elements were expected to provide discrimination. Of these six, only Fe2O3 and SiO2 provided expected, observed and statistical discrimination. Modelling results with this geological approach indicated 36% (+/- 9%) of sediment sampled in the reservoir cores were from mafic-derived sources and 64% (+/- 9%) were from felsic-derived sources. The geological and the first statistical approach (DFA0.05) differed by only 1% (σ 5%) for 5 out of 6 model groupings with only

Improved statistical confirmation of margins for setpoints and transients

International Nuclear Information System (INIS)

Nutt, W.T.

2001-01-01

Framatome ANP Richland, Inc. has developed an integrated, automated, statistical methodology for Pressurized Water Reactors (PWRs). Margins for transients and calculated trips are confirmed using several new applications of probability theory. The methods used for combining statistics reduces the conservatisms inherent in conventional methods and avoids the numerical limitations and time constraints imposed by Monte Carlo techniques. The new methodology represents the state of the art in the treatment of uncertainties for reactor protection systems. It all but eliminates concerns with the calculated trips for PWRs and by improving the margin for all transients will allow for far more aggressive peaking limits and fuel management schemes. The automated nature of the bulk of this process saves Framatome ANP time and effort, minimizes the potential for errors and makes the analysis for all cycles and plants consistent. The enhanced margins remove analytical limitations from the customer and allow for more economical operation of the plant. (authors)

Improving statistical inference on pathogen densities estimated by quantitative molecular methods: malaria gametocytaemia as a case study.

Science.gov (United States)

Walker, Martin; Basáñez, María-Gloria; Ouédraogo, André Lin; Hermsen, Cornelus; Bousema, Teun; Churcher, Thomas S

2015-01-16

Quantitative molecular methods (QMMs) such as quantitative real-time polymerase chain reaction (q-PCR), reverse-transcriptase PCR (qRT-PCR) and quantitative nucleic acid sequence-based amplification (QT-NASBA) are increasingly used to estimate pathogen density in a variety of clinical and epidemiological contexts. These methods are often classified as semi-quantitative, yet estimates of reliability or sensitivity are seldom reported. Here, a statistical framework is developed for assessing the reliability (uncertainty) of pathogen densities estimated using QMMs and the associated diagnostic sensitivity. The method is illustrated with quantification of Plasmodium falciparum gametocytaemia by QT-NASBA. The reliability of pathogen (e.g. gametocyte) densities, and the accompanying diagnostic sensitivity, estimated by two contrasting statistical calibration techniques, are compared; a traditional method and a mixed model Bayesian approach. The latter accounts for statistical dependence of QMM assays run under identical laboratory protocols and permits structural modelling of experimental measurements, allowing precision to vary with pathogen density. Traditional calibration cannot account for inter-assay variability arising from imperfect QMMs and generates estimates of pathogen density that have poor reliability, are variable among assays and inaccurately reflect diagnostic sensitivity. The Bayesian mixed model approach assimilates information from replica QMM assays, improving reliability and inter-assay homogeneity, providing an accurate appraisal of quantitative and diagnostic performance. Bayesian mixed model statistical calibration supersedes traditional techniques in the context of QMM-derived estimates of pathogen density, offering the potential to improve substantially the depth and quality of clinical and epidemiological inference for a wide variety of pathogens.

Harmonization by simulation: a contribution to comparable international migration statistics in Europe

NARCIS (Netherlands)

Nowok, B.

2010-01-01

In today's globalized world, there is increasing demand for reliable and comparable statistics on international migration. This book contributes to a more profound understanding of the effect of definitional variations on the figures that are reported.The framework developed here for the

A comparative analysis of the statistical properties of large mobile phone calling networks.

Science.gov (United States)

Li, Ming-Xia; Jiang, Zhi-Qiang; Xie, Wen-Jie; Miccichè, Salvatore; Tumminello, Michele; Zhou, Wei-Xing; Mantegna, Rosario N

2014-05-30

Mobile phone calling is one of the most widely used communication methods in modern society. The records of calls among mobile phone users provide us a valuable proxy for the understanding of human communication patterns embedded in social networks. Mobile phone users call each other forming a directed calling network. If only reciprocal calls are considered, we obtain an undirected mutual calling network. The preferential communication behavior between two connected users can be statistically tested and it results in two Bonferroni networks with statistically validated edges. We perform a comparative analysis of the statistical properties of these four networks, which are constructed from the calling records of more than nine million individuals in Shanghai over a period of 110 days. We find that these networks share many common structural properties and also exhibit idiosyncratic features when compared with previously studied large mobile calling networks. The empirical findings provide us an intriguing picture of a representative large social network that might shed new lights on the modelling of large social networks.

Finite-sample instrumental variables inference using an asymptotically pivotal statistic

NARCIS (Netherlands)

Bekker, Paul A.; Kleibergen, Frank

2001-01-01

The paper considers the K-statistic, Kleibergen’s (2000) adaptation of the Anderson-Rubin (AR) statistic in instrumental variables regression. Compared to the AR-statistic this K-statistic shows improved asymptotic efficiency in terms of degrees of freedom in overidenti?ed models and yet it shares,

COMPARATIVE STATISTICAL ANALYSIS OF GENOTYPES’ COMBINING

Directory of Open Access Journals (Sweden)

V. Z. Stetsyuk

2015-05-01

The program provides the creation of desktop program complex for statistics calculations on a personal computer of doctor. Modern methods and tools for development of information systems were described to create program.

Statistical approaches in published ophthalmic clinical science papers: a comparison to statistical practice two decades ago.

Science.gov (United States)

Zhang, Harrison G; Ying, Gui-Shuang

2018-02-09

The aim of this study is to evaluate the current practice of statistical analysis of eye data in clinical science papers published in British Journal of Ophthalmology ( BJO ) and to determine whether the practice of statistical analysis has improved in the past two decades. All clinical science papers (n=125) published in BJO in January-June 2017 were reviewed for their statistical analysis approaches for analysing primary ocular measure. We compared our findings to the results from a previous paper that reviewed BJO papers in 1995. Of 112 papers eligible for analysis, half of the studies analysed the data at an individual level because of the nature of observation, 16 (14%) studies analysed data from one eye only, 36 (32%) studies analysed data from both eyes at ocular level, one study (1%) analysed the overall summary of ocular finding per individual and three (3%) studies used the paired comparison. Among studies with data available from both eyes, 50 (89%) of 56 papers in 2017 did not analyse data from both eyes or ignored the intereye correlation, as compared with in 60 (90%) of 67 papers in 1995 (P=0.96). Among studies that analysed data from both eyes at an ocular level, 33 (92%) of 36 studies completely ignored the intereye correlation in 2017, as compared with in 16 (89%) of 18 studies in 1995 (P=0.40). A majority of studies did not analyse the data properly when data from both eyes were available. The practice of statistical analysis did not improve in the past two decades. Collaborative efforts should be made in the vision research community to improve the practice of statistical analysis for ocular data. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Toward Global Comparability of Sexual Orientation Data in Official Statistics: A Conceptual Framework of Sexual Orientation for Health Data Collection in New Zealand’s Official Statistics System

Directory of Open Access Journals (Sweden)

Frank Pega

2013-01-01

Full Text Available Objective. Effectively addressing health disparities experienced by sexual minority populations requires high-quality official data on sexual orientation. We developed a conceptual framework of sexual orientation to improve the quality of sexual orientation data in New Zealand’s Official Statistics System. Methods. We reviewed conceptual and methodological literature, culminating in a draft framework. To improve the framework, we held focus groups and key-informant interviews with sexual minority stakeholders and producers and consumers of official statistics. An advisory board of experts provided additional guidance. Results. The framework proposes working definitions of the sexual orientation topic and measurement concepts, describes dimensions of the measurement concepts, discusses variables framing the measurement concepts, and outlines conceptual grey areas. Conclusion. The framework proposes standard definitions and concepts for the collection of official sexual orientation data in New Zealand. It presents a model for producers of official statistics in other countries, who wish to improve the quality of health data on their citizens.

Using robust statistics to improve neutron activation analysis results

International Nuclear Information System (INIS)

Zahn, Guilherme S.; Genezini, Frederico A.; Ticianelli, Regina B.; Figueiredo, Ana Maria G.

2011-01-01

Neutron activation analysis (NAA) is an analytical technique where an unknown sample is submitted to a neutron flux in a nuclear reactor, and its elemental composition is calculated by measuring the induced activity produced. By using the relative NAA method, one or more well-characterized samples (usually certified reference materials - CRMs) are irradiated together with the unknown ones, and the concentration of each element is then calculated by comparing the areas of the gamma ray peaks related to that element. When two or more CRMs are used as reference, the concentration of each element can be determined by several different ways, either using more than one gamma ray peak for that element (when available), or using the results obtained in the comparison with each CRM. Therefore, determining the best estimate for the concentration of each element in the sample can be a delicate issue. In this work, samples from three CRMs were irradiated together and the elemental concentration in one of them was calculated using the other two as reference. Two sets of peaks were analyzed for each element: a smaller set containing only the literature-recommended gamma-ray peaks and a larger one containing all peaks related to that element that could be quantified in the gamma-ray spectra; the most recommended transition was also used as a benchmark. The resulting data for each element was then reduced using up to five different statistical approaches: the usual (and not robust) unweighted and weighted means, together with three robust means: the Limitation of Relative Statistical Weight, Normalized Residuals and Rajeval. The resulting concentration values were then compared to the certified value for each element, allowing for discussion on both the performance of each statistical tool and on the best choice of peaks for each element. (author)

Strain improvement and statistical optimization as a combined strategy for improving fructosyltransferase production by Aureobasidium pullulans NAC8

Directory of Open Access Journals (Sweden)

Adedeji Nelson Ademakinwa

2017-12-01

A relatively low FTase-producing strain of Aureobasidium pullulans NAC8 was enhanced for optimum production using a two-pronged approach involving mutagenesis and statistical optimization. The improved mutant strain also had remarkable biotechnological properties that make it a suitable alternative than the wild-type.

Improving GEFS Weather Forecasts for Indian Monsoon with Statistical Downscaling

Science.gov (United States)

Agrawal, Ankita; Salvi, Kaustubh; Ghosh, Subimal

2014-05-01

established between the principal components and observed rainfall over training period and predictions are obtained for testing period. The validations show high improvements in correlation coefficient between observed and predicted data (0.25 to 0.55). The results speak in favour of statistical downscaling methodology which shows the capability to reduce the gap between observed data and predictions. A detailed study is required to be carried out by applying different downscaling techniques to quantify the improvements in predictions.

An exercise in model validation: Comparing univariate statistics and Monte Carlo-based multivariate statistics

International Nuclear Information System (INIS)

Weathers, J.B.; Luck, R.; Weathers, J.W.

2009-01-01

The complexity of mathematical models used by practicing engineers is increasing due to the growing availability of sophisticated mathematical modeling tools and ever-improving computational power. For this reason, the need to define a well-structured process for validating these models against experimental results has become a pressing issue in the engineering community. This validation process is partially characterized by the uncertainties associated with the modeling effort as well as the experimental results. The net impact of the uncertainties on the validation effort is assessed through the 'noise level of the validation procedure', which can be defined as an estimate of the 95% confidence uncertainty bounds for the comparison error between actual experimental results and model-based predictions of the same quantities of interest. Although general descriptions associated with the construction of the noise level using multivariate statistics exists in the literature, a detailed procedure outlining how to account for the systematic and random uncertainties is not available. In this paper, the methodology used to derive the covariance matrix associated with the multivariate normal pdf based on random and systematic uncertainties is examined, and a procedure used to estimate this covariance matrix using Monte Carlo analysis is presented. The covariance matrices are then used to construct approximate 95% confidence constant probability contours associated with comparison error results for a practical example. In addition, the example is used to show the drawbacks of using a first-order sensitivity analysis when nonlinear local sensitivity coefficients exist. Finally, the example is used to show the connection between the noise level of the validation exercise calculated using multivariate and univariate statistics.

An exercise in model validation: Comparing univariate statistics and Monte Carlo-based multivariate statistics

Energy Technology Data Exchange (ETDEWEB)

Weathers, J.B. [Shock, Noise, and Vibration Group, Northrop Grumman Shipbuilding, P.O. Box 149, Pascagoula, MS 39568 (United States)], E-mail: James.Weathers@ngc.com; Luck, R. [Department of Mechanical Engineering, Mississippi State University, 210 Carpenter Engineering Building, P.O. Box ME, Mississippi State, MS 39762-5925 (United States)], E-mail: Luck@me.msstate.edu; Weathers, J.W. [Structural Analysis Group, Northrop Grumman Shipbuilding, P.O. Box 149, Pascagoula, MS 39568 (United States)], E-mail: Jeffrey.Weathers@ngc.com

2009-11-15

The complexity of mathematical models used by practicing engineers is increasing due to the growing availability of sophisticated mathematical modeling tools and ever-improving computational power. For this reason, the need to define a well-structured process for validating these models against experimental results has become a pressing issue in the engineering community. This validation process is partially characterized by the uncertainties associated with the modeling effort as well as the experimental results. The net impact of the uncertainties on the validation effort is assessed through the 'noise level of the validation procedure', which can be defined as an estimate of the 95% confidence uncertainty bounds for the comparison error between actual experimental results and model-based predictions of the same quantities of interest. Although general descriptions associated with the construction of the noise level using multivariate statistics exists in the literature, a detailed procedure outlining how to account for the systematic and random uncertainties is not available. In this paper, the methodology used to derive the covariance matrix associated with the multivariate normal pdf based on random and systematic uncertainties is examined, and a procedure used to estimate this covariance matrix using Monte Carlo analysis is presented. The covariance matrices are then used to construct approximate 95% confidence constant probability contours associated with comparison error results for a practical example. In addition, the example is used to show the drawbacks of using a first-order sensitivity analysis when nonlinear local sensitivity coefficients exist. Finally, the example is used to show the connection between the noise level of the validation exercise calculated using multivariate and univariate statistics.

Improving alignment in Tract-based spatial statistics: evaluation and optimization of image registration.

Science.gov (United States)

de Groot, Marius; Vernooij, Meike W; Klein, Stefan; Ikram, M Arfan; Vos, Frans M; Smith, Stephen M; Niessen, Wiro J; Andersson, Jesper L R

2013-08-01

Anatomical alignment in neuroimaging studies is of such importance that considerable effort is put into improving the registration used to establish spatial correspondence. Tract-based spatial statistics (TBSS) is a popular method for comparing diffusion characteristics across subjects. TBSS establishes spatial correspondence using a combination of nonlinear registration and a "skeleton projection" that may break topological consistency of the transformed brain images. We therefore investigated feasibility of replacing the two-stage registration-projection procedure in TBSS with a single, regularized, high-dimensional registration. To optimize registration parameters and to evaluate registration performance in diffusion MRI, we designed an evaluation framework that uses native space probabilistic tractography for 23 white matter tracts, and quantifies tract similarity across subjects in standard space. We optimized parameters for two registration algorithms on two diffusion datasets of different quality. We investigated reproducibility of the evaluation framework, and of the optimized registration algorithms. Next, we compared registration performance of the regularized registration methods and TBSS. Finally, feasibility and effect of incorporating the improved registration in TBSS were evaluated in an example study. The evaluation framework was highly reproducible for both algorithms (R(2) 0.993; 0.931). The optimal registration parameters depended on the quality of the dataset in a graded and predictable manner. At optimal parameters, both algorithms outperformed the registration of TBSS, showing feasibility of adopting such approaches in TBSS. This was further confirmed in the example experiment. Copyright © 2013 Elsevier Inc. All rights reserved.

Introductory Statistics Education and the National Science Foundation

Science.gov (United States)

Hall, Megan R.; Rowell, Ginger Holmes

2008-01-01

This paper describes 27 National Science Foundation supported grant projects that have innovations designed to improve teaching and learning in introductory statistics courses. The characteristics of these projects are compared with the six recommendations given in the "Guidelines for Assessment and Instruction in Statistics Education (GAISE)…

An Improved Rank Correlation Effect Size Statistic for Single-Case Designs: Baseline Corrected Tau.

Science.gov (United States)

Tarlow, Kevin R

2017-07-01

Measuring treatment effects when an individual's pretreatment performance is improving poses a challenge for single-case experimental designs. It may be difficult to determine whether improvement is due to the treatment or due to the preexisting baseline trend. Tau- U is a popular single-case effect size statistic that purports to control for baseline trend. However, despite its strengths, Tau- U has substantial limitations: Its values are inflated and not bound between -1 and +1, it cannot be visually graphed, and its relatively weak method of trend control leads to unacceptable levels of Type I error wherein ineffective treatments appear effective. An improved effect size statistic based on rank correlation and robust regression, Baseline Corrected Tau, is proposed and field-tested with both published and simulated single-case time series. A web-based calculator for Baseline Corrected Tau is also introduced for use by single-case investigators.

Geometric Positioning Accuracy Improvement of ZY-3 Satellite Imagery Based on Statistical Learning Theory

Directory of Open Access Journals (Sweden)

Niangang Jiao

2018-05-01

Full Text Available With the increasing demand for high-resolution remote sensing images for mapping and monitoring the Earth’s environment, geometric positioning accuracy improvement plays a significant role in the image preprocessing step. Based on the statistical learning theory, we propose a new method to improve the geometric positioning accuracy without ground control points (GCPs. Multi-temporal images from the ZY-3 satellite are tested and the bias-compensated rational function model (RFM is applied as the block adjustment model in our experiment. An easy and stable weight strategy and the fast iterative shrinkage-thresholding (FIST algorithm which is widely used in the field of compressive sensing are improved and utilized to define the normal equation matrix and solve it. Then, the residual errors after traditional block adjustment are acquired and tested with the newly proposed inherent error compensation model based on statistical learning theory. The final results indicate that the geometric positioning accuracy of ZY-3 satellite imagery can be improved greatly with our proposed method.

Improving Statistical Literacy in Schools in Australia

OpenAIRE

Trewin, Dennis

2005-01-01

We live in the information age. Statistical thinking is a life skill that all Australian children should have. The Statistical Society of Australia (SSAI) and the Australian Bureau of Statistics (ABS) have been working on a strategy to ensure Australian school children acquire a sufficient understanding and appreciation of how data can be acquired and used so they can make informed judgements in their daily lives, as children and then as adults. There is another motive for our work i...

C-terminal motif prediction in eukaryotic proteomes using comparative genomics and statistical over-representation across protein families

Directory of Open Access Journals (Sweden)

Cutler Sean R

2007-06-01

Full Text Available Abstract Background The carboxy termini of proteins are a frequent site of activity for a variety of biologically important functions, ranging from post-translational modification to protein targeting. Several short peptide motifs involved in protein sorting roles and dependent upon their proximity to the C-terminus for proper function have already been characterized. As a limited number of such motifs have been identified, the potential exists for genome-wide statistical analysis and comparative genomics to reveal novel peptide signatures functioning in a C-terminal dependent manner. We have applied a novel methodology to the prediction of C-terminal-anchored peptide motifs involving a simple z-statistic and several techniques for improving the signal-to-noise ratio. Results We examined the statistical over-representation of position-specific C-terminal tripeptides in 7 eukaryotic proteomes. Sequence randomization models and simple-sequence masking were applied to the successful reduction of background noise. Similarly, as C-terminal homology among members of large protein families may artificially inflate tripeptide counts in an irrelevant and obfuscating manner, gene-family clustering was performed prior to the analysis in order to assess tripeptide over-representation across protein families as opposed to across all proteins. Finally, comparative genomics was used to identify tripeptides significantly occurring in multiple species. This approach has been able to predict, to our knowledge, all C-terminally anchored targeting motifs present in the literature. These include the PTS1 peroxisomal targeting signal (SKL*, the ER-retention signal (K/HDEL*, the ER-retrieval signal for membrane bound proteins (KKxx*, the prenylation signal (CC* and the CaaX box prenylation motif. In addition to a high statistical over-representation of these known motifs, a collection of significant tripeptides with a high propensity for biological function exists

Development and testing of improved statistical wind power forecasting methods.

Energy Technology Data Exchange (ETDEWEB)

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

2011-12-06

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

Statistical Methods for Comparative Phenomics Using High-Throughput Phenotype Microarrays

KAUST Repository

Sturino, Joseph

2010-01-24

We propose statistical methods for comparing phenomics data generated by the Biolog Phenotype Microarray (PM) platform for high-throughput phenotyping. Instead of the routinely used visual inspection of data with no sound inferential basis, we develop two approaches. The first approach is based on quantifying the distance between mean or median curves from two treatments and then applying a permutation test; we also consider a permutation test applied to areas under mean curves. The second approach employs functional principal component analysis. Properties of the proposed methods are investigated on both simulated data and data sets from the PM platform.

Can We Use Polya’s Method to Improve Students’ Performance in the Statistics Classes?

Directory of Open Access Journals (Sweden)

Indika Wickramasinghe

2015-01-01

Full Text Available In this study, Polya’s problem-solving method is introduced in a statistics class in an effort to enhance students’ performance. Teaching the method was applied to one of the two introductory-level statistics classes taught by the same instructor, and a comparison was made between the performances in the two classes. The results indicate there was a significant improvement of the students’ performance in the class in which Polya’s method was introduced.

Reducing statistics anxiety and enhancing statistics learning achievement: effectiveness of a one-minute strategy.

Science.gov (United States)

Chiou, Chei-Chang; Wang, Yu-Min; Lee, Li-Tze

2014-08-01

Statistical knowledge is widely used in academia; however, statistics teachers struggle with the issue of how to reduce students' statistics anxiety and enhance students' statistics learning. This study assesses the effectiveness of a "one-minute paper strategy" in reducing students' statistics-related anxiety and in improving students' statistics-related achievement. Participants were 77 undergraduates from two classes enrolled in applied statistics courses. An experiment was implemented according to a pretest/posttest comparison group design. The quasi-experimental design showed that the one-minute paper strategy significantly reduced students' statistics anxiety and improved students' statistics learning achievement. The strategy was a better instructional tool than the textbook exercise for reducing students' statistics anxiety and improving students' statistics achievement.

Improving the Statistical Modeling of the TRMM Extreme Precipitation Monitoring System

Science.gov (United States)

Demirdjian, L.; Zhou, Y.; Huffman, G. J.

2016-12-01

This project improves upon an existing extreme precipitation monitoring system based on the Tropical Rainfall Measuring Mission (TRMM) daily product (3B42) using new statistical models. The proposed system utilizes a regional modeling approach, where data from similar grid locations are pooled to increase the quality and stability of the resulting model parameter estimates to compensate for the short data record. The regional frequency analysis is divided into two stages. In the first stage, the region defined by the TRMM measurements is partitioned into approximately 27,000 non-overlapping clusters using a recursive k-means clustering scheme. In the second stage, a statistical model is used to characterize the extreme precipitation events occurring in each cluster. Instead of utilizing the block-maxima approach used in the existing system, where annual maxima are fit to the Generalized Extreme Value (GEV) probability distribution at each cluster separately, the present work adopts the peak-over-threshold (POT) method of classifying points as extreme if they exceed a pre-specified threshold. Theoretical considerations motivate the use of the Generalized-Pareto (GP) distribution for fitting threshold exceedances. The fitted parameters can be used to construct simple and intuitive average recurrence interval (ARI) maps which reveal how rare a particular precipitation event is given its spatial location. The new methodology eliminates much of the random noise that was produced by the existing models due to a short data record, producing more reasonable ARI maps when compared with NOAA's long-term Climate Prediction Center (CPC) ground based observations. The resulting ARI maps can be useful for disaster preparation, warning, and management, as well as increased public awareness of the severity of precipitation events. Furthermore, the proposed methodology can be applied to various other extreme climate records.

Measuring and improving the quality of postoperative epidural analgesia for major abdominal surgery using statistical process control charts.

Science.gov (United States)

Duncan, Fiona; Haigh, Carol

2013-10-01

To explore and improve the quality of continuous epidural analgesia for pain relief using Statistical Process Control tools. Measuring the quality of pain management interventions is complex. Intermittent audits do not accurately capture the results of quality improvement initiatives. The failure rate for one intervention, epidural analgesia, is approximately 30% in everyday practice, so it is an important area for improvement. Continuous measurement and analysis are required to understand the multiple factors involved in providing effective pain relief. Process control and quality improvement Routine prospectively acquired data collection started in 2006. Patients were asked about their pain and side effects of treatment. Statistical Process Control methods were applied for continuous data analysis. A multidisciplinary group worked together to identify reasons for variation in the data and instigated ideas for improvement. The key measure for improvement was a reduction in the percentage of patients with an epidural in severe pain. The baseline control charts illustrated the recorded variation in the rate of several processes and outcomes for 293 surgical patients. The mean visual analogue pain score (VNRS) was four. There was no special cause variation when data were stratified by surgeons, clinical area or patients who had experienced pain before surgery. Fifty-seven per cent of patients were hypotensive on the first day after surgery. We were able to demonstrate a significant improvement in the failure rate of epidurals as the project continued with quality improvement interventions. Statistical Process Control is a useful tool for measuring and improving the quality of pain management. The applications of Statistical Process Control methods offer the potential to learn more about the process of change and outcomes in an Acute Pain Service both locally and nationally. We have been able to develop measures for improvement and benchmarking in routine care that

Rainfall Downscaling Conditional on Upper-air Atmospheric Predictors: Improved Assessment of Rainfall Statistics in a Changing Climate

Science.gov (United States)

Langousis, Andreas; Mamalakis, Antonis; Deidda, Roberto; Marrocu, Marino

2015-04-01

To improve the level skill of Global Climate Models (GCMs) and Regional Climate Models (RCMs) in reproducing the statistics of rainfall at a basin level and at hydrologically relevant temporal scales (e.g. daily), two types of statistical approaches have been suggested. One is the statistical correction of climate model rainfall outputs using historical series of precipitation. The other is the use of stochastic models of rainfall to conditionally simulate precipitation series, based on large-scale atmospheric predictors produced by climate models (e.g. geopotential height, relative vorticity, divergence, mean sea level pressure). The latter approach, usually referred to as statistical rainfall downscaling, aims at reproducing the statistical character of rainfall, while accounting for the effects of large-scale atmospheric circulation (and, therefore, climate forcing) on rainfall statistics. While promising, statistical rainfall downscaling has not attracted much attention in recent years, since the suggested approaches involved complex (i.e. subjective or computationally intense) identification procedures of the local weather, in addition to demonstrating limited success in reproducing several statistical features of rainfall, such as seasonal variations, the distributions of dry and wet spell lengths, the distribution of the mean rainfall intensity inside wet periods, and the distribution of rainfall extremes. In an effort to remedy those shortcomings, Langousis and Kaleris (2014) developed a statistical framework for simulation of daily rainfall intensities conditional on upper air variables, which accurately reproduces the statistical character of rainfall at multiple time-scales. Here, we study the relative performance of: a) quantile-quantile (Q-Q) correction of climate model rainfall products, and b) the statistical downscaling scheme of Langousis and Kaleris (2014), in reproducing the statistical structure of rainfall, as well as rainfall extremes, at a

Statistical conditional sampling for variable-resolution video compression.

Directory of Open Access Journals (Sweden)

Alexander Wong

Full Text Available In this study, we investigate a variable-resolution approach to video compression based on Conditional Random Field and statistical conditional sampling in order to further improve compression rate while maintaining high-quality video. In the proposed approach, representative key-frames within a video shot are identified and stored at full resolution. The remaining frames within the video shot are stored and compressed at a reduced resolution. At the decompression stage, a region-based dictionary is constructed from the key-frames and used to restore the reduced resolution frames to the original resolution via statistical conditional sampling. The sampling approach is based on the conditional probability of the CRF modeling by use of the constructed dictionary. Experimental results show that the proposed variable-resolution approach via statistical conditional sampling has potential for improving compression rates when compared to compressing the video at full resolution, while achieving higher video quality when compared to compressing the video at reduced resolution.

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

Science.gov (United States)

Morris, Nathan; Elston, Robert

2011-01-01

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

Localization Improvement in Wireless Sensor Networks Using a New Statistical Channel Model

DEFF Research Database (Denmark)

Karimi Alavijeh, Amir; Ramezani, Hossein; Karimi Alavijeh, Ali

2018-01-01

of this statistical relationship, we have investigated the localization problem of a hidden node using extended Kalman filter (EKF). Compared to the conventional EKF in which the covariance matrix of measurement noise is fixed, this matrix can be updated online using the proposed model. The experimental...

Improved air ventilation rate estimation based on a statistical model

International Nuclear Information System (INIS)

Brabec, M.; Jilek, K.

2004-01-01

A new approach to air ventilation rate estimation from CO measurement data is presented. The approach is based on a state-space dynamic statistical model, allowing for quick and efficient estimation. Underlying computations are based on Kalman filtering, whose practical software implementation is rather easy. The key property is the flexibility of the model, allowing various artificial regimens of CO level manipulation to be treated. The model is semi-parametric in nature and can efficiently handle time-varying ventilation rate. This is a major advantage, compared to some of the methods which are currently in practical use. After a formal introduction of the statistical model, its performance is demonstrated on real data from routine measurements. It is shown how the approach can be utilized in a more complex situation of major practical relevance, when time-varying air ventilation rate and radon entry rate are to be estimated simultaneously from concurrent radon and CO measurements

A Comparative Study of Effectiveness of Neurofeedback and Ritalin on Improving Conduct Problems and Hyperactivity

Directory of Open Access Journals (Sweden)

K. Khoushabi

2012-01-01

Full Text Available Introduction & Objective: There are varieties of interventions to treatment of ADHD, among which drug therapy, behavior therapy, parental management training and neurofeedback can be cited. The present study designed to investigate and compare the effectiveness of neurofeedback and Ritalin on improving conduct problems and hyperactivity. Materials & Methods: Quasi-experimental research method with pretest-post test design has been applied in the research. Statistical population of the study consisted of ADHD children of Tehran. The study samples of the study were patients referred to children psychiatric clinic. Based on the purpose of the study' 20 children were randomly selected and classified into 2 groups according to random assignment. CPRS-48 (parent form was administered by parents before and after the treatments as research tools. Recruited data was analyzed by SPSS-19 in two sections of descriptive and inferential statistics. ANCOVA revealed some differences in the groups. Results: The findings of the study showed that there was a significant difference between Ritalin and neurofeedback on improving conduct problems; in other words, Ritalin was more effective in alleviating the problems. Also there was no significant difference between the interventions on improving hyperactivity index. Conclusion: With respect to more efficiency of Ritalin than neurofeedback on certain continuum of signs/symptoms of ADHD, as a whole, preferences of interventions should be based on type, magnitude and severity of the syndrome(Sci J Hamadan Univ Med Sci 2012;18(4:53-59

Homicides by Police: Comparing Counts From the National Violent Death Reporting System, Vital Statistics, and Supplementary Homicide Reports.

Science.gov (United States)

Barber, Catherine; Azrael, Deborah; Cohen, Amy; Miller, Matthew; Thymes, Deonza; Wang, David Enze; Hemenway, David

2016-05-01

To evaluate the National Violent Death Reporting System (NVDRS) as a surveillance system for homicides by law enforcement officers. We assessed sensitivity and positive predictive value of the NVDRS "type of death" variable against our study count of homicides by police, which we derived from NVDRS coded and narrative data for states participating in NVDRS 2005 to 2012. We compared state counts of police homicides from NVDRS, Vital Statistics, and Federal Bureau of Investigation Supplementary Homicide Reports. We identified 1552 police homicides in the 16 states. Positive predictive value and sensitivity of the NVDRS "type of death" variable for police homicides were high (98% and 90%, respectively). Counts from Vital Statistics and Supplementary Homicide Reports were 58% and 48%, respectively, of our study total; gaps varied widely by state. The annual rate of police homicide (0.24/100,000) varied 5-fold by state and 8-fold by race/ethnicity. NVDRS provides more complete data on police homicides than do existing systems. Expanding NVDRS to all 50 states and making 2 improvements we identify will be an efficient way to provide the nation with more accurate, detailed data on homicides by law enforcement.

Stochastic or statistic? Comparing flow duration curve models in ungauged basins and changing climates

Science.gov (United States)

Müller, M. F.; Thompson, S. E.

2015-09-01

The prediction of flow duration curves (FDCs) in ungauged basins remains an important task for hydrologists given the practical relevance of FDCs for water management and infrastructure design. Predicting FDCs in ungauged basins typically requires spatial interpolation of statistical or model parameters. This task is complicated if climate becomes non-stationary, as the prediction challenge now also requires extrapolation through time. In this context, process-based models for FDCs that mechanistically link the streamflow distribution to climate and landscape factors may have an advantage over purely statistical methods to predict FDCs. This study compares a stochastic (process-based) and statistical method for FDC prediction in both stationary and non-stationary contexts, using Nepal as a case study. Under contemporary conditions, both models perform well in predicting FDCs, with Nash-Sutcliffe coefficients above 0.80 in 75 % of the tested catchments. The main drives of uncertainty differ between the models: parameter interpolation was the main source of error for the statistical model, while violations of the assumptions of the process-based model represented the main source of its error. The process-based approach performed better than the statistical approach in numerical simulations with non-stationary climate drivers. The predictions of the statistical method under non-stationary rainfall conditions were poor if (i) local runoff coefficients were not accurately determined from the gauge network, or (ii) streamflow variability was strongly affected by changes in rainfall. A Monte Carlo analysis shows that the streamflow regimes in catchments characterized by a strong wet-season runoff and a rapid, strongly non-linear hydrologic response are particularly sensitive to changes in rainfall statistics. In these cases, process-based prediction approaches are strongly favored over statistical models.

Improving Instruction Using Statistical Process Control.

Science.gov (United States)

Higgins, Ronald C.; Messer, George H.

1990-01-01

Two applications of statistical process control to the process of education are described. Discussed are the use of prompt feedback to teachers and prompt feedback to students. A sample feedback form is provided. (CW)

Comparably improved health-related quality of life after total arterial revascularization versus conventional coronary surgery--Copenhagen arterial revascularization randomized patency and outcome trial

DEFF Research Database (Denmark)

Damgaard, Sune; Lund, Jens T; Lilleør, Nikolaj B

2011-01-01

OBJECTIVE: We compared health-related quality of life up to 11 months after coronary artery bypass grafting using total arterial revascularization versus conventional coronary surgery. METHODS: In this randomized single-center trial, 161 patients underwent total arterial revascularization using.......01). For total arterial revascularization, there were also not statistically significant improvements for 'physical component summary' (P=0.09), 'bodily pain' (P=0.07) and 'vitality' (P=0.08). CONCLUSION: Health-related quality of life up to 1 year after total arterial revascularization is equal or slightly...... of the general Danish population. On all scales of the SF-36, there was statistically significant improvement at 3 and 11 months in both groups. For 'social functioning', the improvement following total arterial revascularization was significantly higher than following conventional revascularization (P=0...

Robustness of S1 statistic with Hodges-Lehmann for skewed distributions

Science.gov (United States)

Ahad, Nor Aishah; Yahaya, Sharipah Soaad Syed; Yin, Lee Ping

2016-10-01

Analysis of variance (ANOVA) is a common use parametric method to test the differences in means for more than two groups when the populations are normally distributed. ANOVA is highly inefficient under the influence of non- normal and heteroscedastic settings. When the assumptions are violated, researchers are looking for alternative such as Kruskal-Wallis under nonparametric or robust method. This study focused on flexible method, S1 statistic for comparing groups using median as the location estimator. S1 statistic was modified by substituting the median with Hodges-Lehmann and the default scale estimator with the variance of Hodges-Lehmann and MADn to produce two different test statistics for comparing groups. Bootstrap method was used for testing the hypotheses since the sampling distributions of these modified S1 statistics are unknown. The performance of the proposed statistic in terms of Type I error was measured and compared against the original S1 statistic, ANOVA and Kruskal-Wallis. The propose procedures show improvement compared to the original statistic especially under extremely skewed distribution.

Improved statistical models for limited datasets in uncertainty quantification using stochastic collocation

Energy Technology Data Exchange (ETDEWEB)

Alwan, Aravind; Aluru, N.R.

2013-12-15

This paper presents a data-driven framework for performing uncertainty quantification (UQ) by choosing a stochastic model that accurately describes the sources of uncertainty in a system. This model is propagated through an appropriate response surface function that approximates the behavior of this system using stochastic collocation. Given a sample of data describing the uncertainty in the inputs, our goal is to estimate a probability density function (PDF) using the kernel moment matching (KMM) method so that this PDF can be used to accurately reproduce statistics like mean and variance of the response surface function. Instead of constraining the PDF to be optimal for a particular response function, we show that we can use the properties of stochastic collocation to make the estimated PDF optimal for a wide variety of response functions. We contrast this method with other traditional procedures that rely on the Maximum Likelihood approach, like kernel density estimation (KDE) and its adaptive modification (AKDE). We argue that this modified KMM method tries to preserve what is known from the given data and is the better approach when the available data is limited in quantity. We test the performance of these methods for both univariate and multivariate density estimation by sampling random datasets from known PDFs and then measuring the accuracy of the estimated PDFs, using the known PDF as a reference. Comparing the output mean and variance estimated with the empirical moments using the raw data sample as well as the actual moments using the known PDF, we show that the KMM method performs better than KDE and AKDE in predicting these moments with greater accuracy. This improvement in accuracy is also demonstrated for the case of UQ in electrostatic and electrothermomechanical microactuators. We show how our framework results in the accurate computation of statistics in micromechanical systems.

Improved statistical models for limited datasets in uncertainty quantification using stochastic collocation

International Nuclear Information System (INIS)

Alwan, Aravind; Aluru, N.R.

2013-01-01

This paper presents a data-driven framework for performing uncertainty quantification (UQ) by choosing a stochastic model that accurately describes the sources of uncertainty in a system. This model is propagated through an appropriate response surface function that approximates the behavior of this system using stochastic collocation. Given a sample of data describing the uncertainty in the inputs, our goal is to estimate a probability density function (PDF) using the kernel moment matching (KMM) method so that this PDF can be used to accurately reproduce statistics like mean and variance of the response surface function. Instead of constraining the PDF to be optimal for a particular response function, we show that we can use the properties of stochastic collocation to make the estimated PDF optimal for a wide variety of response functions. We contrast this method with other traditional procedures that rely on the Maximum Likelihood approach, like kernel density estimation (KDE) and its adaptive modification (AKDE). We argue that this modified KMM method tries to preserve what is known from the given data and is the better approach when the available data is limited in quantity. We test the performance of these methods for both univariate and multivariate density estimation by sampling random datasets from known PDFs and then measuring the accuracy of the estimated PDFs, using the known PDF as a reference. Comparing the output mean and variance estimated with the empirical moments using the raw data sample as well as the actual moments using the known PDF, we show that the KMM method performs better than KDE and AKDE in predicting these moments with greater accuracy. This improvement in accuracy is also demonstrated for the case of UQ in electrostatic and electrothermomechanical microactuators. We show how our framework results in the accurate computation of statistics in micromechanical systems

Adaptive statistical iterative reconstruction for volume-rendered computed tomography portovenography. Improvement of image quality

International Nuclear Information System (INIS)

Matsuda, Izuru; Hanaoka, Shohei; Akahane, Masaaki

2010-01-01

Adaptive statistical iterative reconstruction (ASIR) is a reconstruction technique for computed tomography (CT) that reduces image noise. The purpose of our study was to investigate whether ASIR improves the quality of volume-rendered (VR) CT portovenography. Institutional review board approval, with waived consent, was obtained. A total of 19 patients (12 men, 7 women; mean age 69.0 years; range 25-82 years) suspected of having liver lesions underwent three-phase enhanced CT. VR image sets were prepared with both the conventional method and ASIR. The required time to make VR images was recorded. Two radiologists performed independent qualitative evaluations of the image sets. The Wilcoxon signed-rank test was used for statistical analysis. Contrast-noise ratios (CNRs) of the portal and hepatic vein were also evaluated. Overall image quality was significantly improved by ASIR (P<0.0001 and P=0.0155 for each radiologist). ASIR enhanced CNRs of the portal and hepatic vein significantly (P<0.0001). The time required to create VR images was significantly shorter with ASIR (84.7 vs. 117.1 s; P=0.014). ASIR enhances CNRs and improves image quality in VR CT portovenography. It also shortens the time required to create liver VR CT portovenographs. (author)

Application of quality improvement analytic methodology in emergency medicine research: A comparative evaluation.

Science.gov (United States)

Harries, Bruce; Filiatrault, Lyne; Abu-Laban, Riyad B

2018-05-30

Quality improvement (QI) analytic methodology is rarely encountered in the emergency medicine literature. We sought to comparatively apply QI design and analysis techniques to an existing data set, and discuss these techniques as an alternative to standard research methodology for evaluating a change in a process of care. We used data from a previously published randomized controlled trial on triage-nurse initiated radiography using the Ottawa ankle rules (OAR). QI analytic tools were applied to the data set from this study and evaluated comparatively against the original standard research methodology. The original study concluded that triage nurse-initiated radiographs led to a statistically significant decrease in mean emergency department length of stay. Using QI analytic methodology, we applied control charts and interpreted the results using established methods that preserved the time sequence of the data. This analysis found a compelling signal of a positive treatment effect that would have been identified after the enrolment of 58% of the original study sample, and in the 6th month of this 11-month study. Our comparative analysis demonstrates some of the potential benefits of QI analytic methodology. We found that had this approach been used in the original study, insights regarding the benefits of nurse-initiated radiography using the OAR would have been achieved earlier, and thus potentially at a lower cost. In situations where the overarching aim is to accelerate implementation of practice improvement to benefit future patients, we believe that increased consideration should be given to the use of QI analytic methodology.

Do clinical safety charts improve paramedic key performance indicator results? (A clinical improvement programme evaluation).

Science.gov (United States)

Ebbs, Phillip; Middleton, Paul M; Bonner, Ann; Loudfoot, Allan; Elliott, Peter

2012-07-01

Is the Clinical Safety Chart clinical improvement programme (CIP) effective at improving paramedic key performance indicator (KPI) results within the Ambulance Service of New South Wales? The CIP intervention area was compared with the non-intervention area in order to determine whether there was a statistically significant improvement in KPI results. The CIP was associated with a statistically significant improvement in paramedic KPI results within the intervention area. The strategies used within this CIP are recommended for further consideration.

Statistic techniques of process control for MTR type

International Nuclear Information System (INIS)

Oliveira, F.S.; Ferrufino, F.B.J.; Santos, G.R.T.; Lima, R.M.

2002-01-01

This work aims at introducing some improvements on the fabrication of MTR type fuel plates, applying statistic techniques of process control. The work was divided into four single steps and their data were analyzed for: fabrication of U 3 O 8 fuel plates; fabrication of U 3 Si 2 fuel plates; rolling of small lots of fuel plates; applying statistic tools and standard specifications to perform a comparative study of these processes. (author)

Improving Education in Medical Statistics: Implementing a Blended Learning Model in the Existing Curriculum

Science.gov (United States)

Milic, Natasa M.; Trajkovic, Goran Z.; Bukumiric, Zoran M.; Cirkovic, Andja; Nikolic, Ivan M.; Milin, Jelena S.; Milic, Nikola V.; Savic, Marko D.; Corac, Aleksandar M.; Marinkovic, Jelena M.; Stanisavljevic, Dejana M.

2016-01-01

Background Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face) learning to further assess the potential value of web-based learning in medical statistics. Methods This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545) the final exam of the obligatory introductory statistics course during 2013–14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course. Results Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001) and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023) with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA) was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (plearning environments for teaching medical statistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional classroom training in medical statistics. PMID:26859832

Preparing systems engineering and computing science students in disciplined methods, quantitative, and advanced statistical techniques to improve process performance

Science.gov (United States)

McCray, Wilmon Wil L., Jr.

The research was prompted by a need to conduct a study that assesses process improvement, quality management and analytical techniques taught to students in U.S. colleges and universities undergraduate and graduate systems engineering and the computing science discipline (e.g., software engineering, computer science, and information technology) degree programs during their academic training that can be applied to quantitatively manage processes for performance. Everyone involved in executing repeatable processes in the software and systems development lifecycle processes needs to become familiar with the concepts of quantitative management, statistical thinking, process improvement methods and how they relate to process-performance. Organizations are starting to embrace the de facto Software Engineering Institute (SEI) Capability Maturity Model Integration (CMMI RTM) Models as process improvement frameworks to improve business processes performance. High maturity process areas in the CMMI model imply the use of analytical, statistical, quantitative management techniques, and process performance modeling to identify and eliminate sources of variation, continually improve process-performance; reduce cost and predict future outcomes. The research study identifies and provides a detail discussion of the gap analysis findings of process improvement and quantitative analysis techniques taught in U.S. universities systems engineering and computing science degree programs, gaps that exist in the literature, and a comparison analysis which identifies the gaps that exist between the SEI's "healthy ingredients " of a process performance model and courses taught in U.S. universities degree program. The research also heightens awareness that academicians have conducted little research on applicable statistics and quantitative techniques that can be used to demonstrate high maturity as implied in the CMMI models. The research also includes a Monte Carlo simulation optimization

Improved model for statistical alignment

Energy Technology Data Exchange (ETDEWEB)

Miklos, I.; Toroczkai, Z. (Zoltan)

2001-01-01

The statistical approach to molecular sequence evolution involves the stochastic modeling of the substitution, insertion and deletion processes. Substitution has been modeled in a reliable way for more than three decades by using finite Markov-processes. Insertion and deletion, however, seem to be more difficult to model, and thc recent approaches cannot acceptably deal with multiple insertions and deletions. A new method based on a generating function approach is introduced to describe the multiple insertion process. The presented algorithm computes the approximate joint probability of two sequences in 0(13) running time where 1 is the geometric mean of the sequence lengths.

Official Statistics and Statistics Education: Bridging the Gap

Directory of Open Access Journals (Sweden)

Gal Iddo

2017-03-01

Full Text Available This article aims to challenge official statistics providers and statistics educators to ponder on how to help non-specialist adult users of statistics develop those aspects of statistical literacy that pertain to official statistics. We first document the gap in the literature in terms of the conceptual basis and educational materials needed for such an undertaking. We then review skills and competencies that may help adults to make sense of statistical information in areas of importance to society. Based on this review, we identify six elements related to official statistics about which non-specialist adult users should possess knowledge in order to be considered literate in official statistics: (1 the system of official statistics and its work principles; (2 the nature of statistics about society; (3 indicators; (4 statistical techniques and big ideas; (5 research methods and data sources; and (6 awareness and skills for citizens’ access to statistical reports. Based on this ad hoc typology, we discuss directions that official statistics providers, in cooperation with statistics educators, could take in order to (1 advance the conceptualization of skills needed to understand official statistics, and (2 expand educational activities and services, specifically by developing a collaborative digital textbook and a modular online course, to improve public capacity for understanding of official statistics.

An Improvement of the Hotelling T2 Statistic in Monitoring Multivariate Quality Characteristics

Directory of Open Access Journals (Sweden)

Ashkan Shabbak

2012-01-01

Full Text Available The Hotelling T2 statistic is the most popular statistic used in multivariate control charts to monitor multiple qualities. However, this statistic is easily affected by the existence of more than one outlier in the data set. To rectify this problem, robust control charts, which are based on the minimum volume ellipsoid and the minimum covariance determinant, have been proposed. Most researchers assess the performance of multivariate control charts based on the number of signals without paying much attention to whether those signals are really outliers. With due respect, we propose to evaluate control charts not only based on the number of detected outliers but also with respect to their correct positions. In this paper, an Upper Control Limit based on the median and the median absolute deviation is also proposed. The results of this study signify that the proposed Upper Control Limit improves the detection of correct outliers but that it suffers from a swamping effect when the positions of outliers are not taken into consideration. Finally, a robust control chart based on the diagnostic robust generalised potential procedure is introduced to remedy this drawback.

Time-to-event methodology improved statistical evaluation in register-based health services research.

Science.gov (United States)

Bluhmki, Tobias; Bramlage, Peter; Volk, Michael; Kaltheuner, Matthias; Danne, Thomas; Rathmann, Wolfgang; Beyersmann, Jan

2017-02-01

Complex longitudinal sampling and the observational structure of patient registers in health services research are associated with methodological challenges regarding data management and statistical evaluation. We exemplify common pitfalls and want to stimulate discussions on the design, development, and deployment of future longitudinal patient registers and register-based studies. For illustrative purposes, we use data from the prospective, observational, German DIabetes Versorgungs-Evaluation register. One aim was to explore predictors for the initiation of a basal insulin supported therapy in patients with type 2 diabetes initially prescribed to glucose-lowering drugs alone. Major challenges are missing mortality information, time-dependent outcomes, delayed study entries, different follow-up times, and competing events. We show that time-to-event methodology is a valuable tool for improved statistical evaluation of register data and should be preferred to simple case-control approaches. Patient registers provide rich data sources for health services research. Analyses are accompanied with the trade-off between data availability, clinical plausibility, and statistical feasibility. Cox' proportional hazards model allows for the evaluation of the outcome-specific hazards, but prediction of outcome probabilities is compromised by missing mortality information. Copyright © 2016 Elsevier Inc. All rights reserved.

Selection of the Maximum Spatial Cluster Size of the Spatial Scan Statistic by Using the Maximum Clustering Set-Proportion Statistic.

Science.gov (United States)

Ma, Yue; Yin, Fei; Zhang, Tao; Zhou, Xiaohua Andrew; Li, Xiaosong

2016-01-01

Spatial scan statistics are widely used in various fields. The performance of these statistics is influenced by parameters, such as maximum spatial cluster size, and can be improved by parameter selection using performance measures. Current performance measures are based on the presence of clusters and are thus inapplicable to data sets without known clusters. In this work, we propose a novel overall performance measure called maximum clustering set-proportion (MCS-P), which is based on the likelihood of the union of detected clusters and the applied dataset. MCS-P was compared with existing performance measures in a simulation study to select the maximum spatial cluster size. Results of other performance measures, such as sensitivity and misclassification, suggest that the spatial scan statistic achieves accurate results in most scenarios with the maximum spatial cluster sizes selected using MCS-P. Given that previously known clusters are not required in the proposed strategy, selection of the optimal maximum cluster size with MCS-P can improve the performance of the scan statistic in applications without identified clusters.

Improving Education in Medical Statistics: Implementing a Blended Learning Model in the Existing Curriculum.

Science.gov (United States)

Milic, Natasa M; Trajkovic, Goran Z; Bukumiric, Zoran M; Cirkovic, Andja; Nikolic, Ivan M; Milin, Jelena S; Milic, Nikola V; Savic, Marko D; Corac, Aleksandar M; Marinkovic, Jelena M; Stanisavljevic, Dejana M

2016-01-01

Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face) learning to further assess the potential value of web-based learning in medical statistics. This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545) the final exam of the obligatory introductory statistics course during 2013-14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course. Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001) and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023) with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA) was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (pstatistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional classroom training in medical statistics.

Severe postpartum haemorrhage after vaginal delivery: a statistical process control chart to report seven years of continuous quality improvement.

Science.gov (United States)

Dupont, Corinne; Occelli, Pauline; Deneux-Tharaux, Catherine; Touzet, Sandrine; Duclos, Antoine; Bouvier-Colle, Marie-Hélène; Rudigoz, René-Charles; Huissoud, Cyril

2014-07-01

Severe postpartum haemorrhage after vaginal delivery: a statistical process control chart to report seven years of continuous quality improvement To use statistical process control charts to describe trends in the prevalence of severe postpartum haemorrhage after vaginal delivery. This assessment was performed 7 years after we initiated a continuous quality improvement programme that began with regular criteria-based audits Observational descriptive study, in a French maternity unit in the Rhône-Alpes region. Quarterly clinical audit meetings to analyse all cases of severe postpartum haemorrhage after vaginal delivery and provide feedback on quality of care with statistical process control tools. The primary outcomes were the prevalence of severe PPH after vaginal delivery and its quarterly monitoring with a control chart. The secondary outcomes included the global quality of care for women with severe postpartum haemorrhage, including the performance rate of each recommended procedure. Differences in these variables between 2005 and 2012 were tested. From 2005 to 2012, the prevalence of severe postpartum haemorrhage declined significantly, from 1.2% to 0.6% of vaginal deliveries (pcontrol limits, that is, been out of statistical control. The proportion of cases that were managed consistently with the guidelines increased for all of their main components. Implementation of continuous quality improvement efforts began seven years ago and used, among other tools, statistical process control charts. During this period, the prevalence of severe postpartum haemorrhage after vaginal delivery has been reduced by 50%. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Analysis of data collected from right and left limbs: Accounting for dependence and improving statistical efficiency in musculoskeletal research.

Science.gov (United States)

Stewart, Sarah; Pearson, Janet; Rome, Keith; Dalbeth, Nicola; Vandal, Alain C

2018-01-01

Statistical techniques currently used in musculoskeletal research often inefficiently account for paired-limb measurements or the relationship between measurements taken from multiple regions within limbs. This study compared three commonly used analysis methods with a mixed-models approach that appropriately accounted for the association between limbs, regions, and trials and that utilised all information available from repeated trials. Four analysis were applied to an existing data set containing plantar pressure data, which was collected for seven masked regions on right and left feet, over three trials, across three participant groups. Methods 1-3 averaged data over trials and analysed right foot data (Method 1), data from a randomly selected foot (Method 2), and averaged right and left foot data (Method 3). Method 4 used all available data in a mixed-effects regression that accounted for repeated measures taken for each foot, foot region and trial. Confidence interval widths for the mean differences between groups for each foot region were used as a criterion for comparison of statistical efficiency. Mean differences in pressure between groups were similar across methods for each foot region, while the confidence interval widths were consistently smaller for Method 4. Method 4 also revealed significant between-group differences that were not detected by Methods 1-3. A mixed effects linear model approach generates improved efficiency and power by producing more precise estimates compared to alternative approaches that discard information in the process of accounting for paired-limb measurements. This approach is recommended in generating more clinically sound and statistically efficient research outputs. Copyright © 2017 Elsevier B.V. All rights reserved.

IMPROVING QUALITY OF STATISTICAL PROCESS CONTROL BY DEALING WITH NON‐NORMAL DATA IN AUTOMOTIVE INDUSTRY

Directory of Open Access Journals (Sweden)

Zuzana ANDRÁSSYOVÁ

2012-07-01

Full Text Available Study deals with an analysis of data to the effect that it improves the quality of statistical tools in processes of assembly of automobile seats. Normal distribution of variables is one of inevitable conditions for the analysis, examination, and improvement of the manufacturing processes (f. e.: manufacturing process capability although, there are constantly more approaches to non‐normal data handling. An appropriate probability distribution of measured data is firstly tested by the goodness of fit of empirical distribution with theoretical normal distribution on the basis of hypothesis testing using programme StatGraphics Centurion XV.II. Data are collected from the assembly process of 1st row automobile seats for each characteristic of quality (Safety Regulation ‐S/R individually. Study closely processes the measured data of an airbag´s assembly and it aims to accomplish the normal distributed data and apply it the statistical process control. Results of the contribution conclude in a statement of rejection of the null hypothesis (measured variables do not follow the normal distribution therefore it is necessary to begin to work on data transformation supported by Minitab15. Even this approach does not reach a normal distributed data and so should be proposed a procedure that leads to the quality output of whole statistical control of manufacturing processes.

Death Certification Errors and the Effect on Mortality Statistics.

Science.gov (United States)

McGivern, Lauri; Shulman, Leanne; Carney, Jan K; Shapiro, Steven; Bundock, Elizabeth

Errors in cause and manner of death on death certificates are common and affect families, mortality statistics, and public health research. The primary objective of this study was to characterize errors in the cause and manner of death on death certificates completed by non-Medical Examiners. A secondary objective was to determine the effects of errors on national mortality statistics. We retrospectively compared 601 death certificates completed between July 1, 2015, and January 31, 2016, from the Vermont Electronic Death Registration System with clinical summaries from medical records. Medical Examiners, blinded to original certificates, reviewed summaries, generated mock certificates, and compared mock certificates with original certificates. They then graded errors using a scale from 1 to 4 (higher numbers indicated increased impact on interpretation of the cause) to determine the prevalence of minor and major errors. They also compared International Classification of Diseases, 10th Revision (ICD-10) codes on original certificates with those on mock certificates. Of 601 original death certificates, 319 (53%) had errors; 305 (51%) had major errors; and 59 (10%) had minor errors. We found no significant differences by certifier type (physician vs nonphysician). We did find significant differences in major errors in place of death ( P statistics. Surveillance and certifier education must expand beyond local and state efforts. Simplifying and standardizing underlying literal text for cause of death may improve accuracy, decrease coding errors, and improve national mortality statistics.

Improved score statistics for meta-analysis in single-variant and gene-level association studies.

Science.gov (United States)

Yang, Jingjing; Chen, Sai; Abecasis, Gonçalo

2018-06-01

Meta-analysis is now an essential tool for genetic association studies, allowing them to combine large studies and greatly accelerating the pace of genetic discovery. Although the standard meta-analysis methods perform equivalently as the more cumbersome joint analysis under ideal settings, they result in substantial power loss under unbalanced settings with various case-control ratios. Here, we investigate the power loss problem by the standard meta-analysis methods for unbalanced studies, and further propose novel meta-analysis methods performing equivalently to the joint analysis under both balanced and unbalanced settings. We derive improved meta-score-statistics that can accurately approximate the joint-score-statistics with combined individual-level data, for both linear and logistic regression models, with and without covariates. In addition, we propose a novel approach to adjust for population stratification by correcting for known population structures through minor allele frequencies. In the simulated gene-level association studies under unbalanced settings, our method recovered up to 85% power loss caused by the standard methods. We further showed the power gain of our methods in gene-level tests with 26 unbalanced studies of age-related macular degeneration . In addition, we took the meta-analysis of three unbalanced studies of type 2 diabetes as an example to discuss the challenges of meta-analyzing multi-ethnic samples. In summary, our improved meta-score-statistics with corrections for population stratification can be used to construct both single-variant and gene-level association studies, providing a useful framework for ensuring well-powered, convenient, cross-study analyses. © 2018 WILEY PERIODICALS, INC.

Improving Education in Medical Statistics: Implementing a Blended Learning Model in the Existing Curriculum.

Directory of Open Access Journals (Sweden)

Natasa M Milic

Full Text Available Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face learning to further assess the potential value of web-based learning in medical statistics.This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545 the final exam of the obligatory introductory statistics course during 2013-14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course.Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001 and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023 with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (p<0.001.This study provides empirical evidence to support educator decisions to implement different learning environments for teaching medical statistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional

Statistical Inference at Work: Statistical Process Control as an Example

Science.gov (United States)

Bakker, Arthur; Kent, Phillip; Derry, Jan; Noss, Richard; Hoyles, Celia

2008-01-01

To characterise statistical inference in the workplace this paper compares a prototypical type of statistical inference at work, statistical process control (SPC), with a type of statistical inference that is better known in educational settings, hypothesis testing. Although there are some similarities between the reasoning structure involved in…

Statistical Reasoning Ability, Self-Efficacy, and Value Beliefs in a University Statistics Course

Science.gov (United States)

Olani, A.; Hoekstra, R.; Harskamp, E.; van der Werf, G.

2011-01-01

Introduction: The study investigated the degree to which students' statistical reasoning abilities, statistics self-efficacy, and perceived value of statistics improved during a reform based introductory statistics course. The study also examined whether the changes in these learning outcomes differed with respect to the students' mathematical…

Comparing statistical and process-based flow duration curve models in ungauged basins and changing rain regimes

Science.gov (United States)

Müller, M. F.; Thompson, S. E.

2016-02-01

The prediction of flow duration curves (FDCs) in ungauged basins remains an important task for hydrologists given the practical relevance of FDCs for water management and infrastructure design. Predicting FDCs in ungauged basins typically requires spatial interpolation of statistical or model parameters. This task is complicated if climate becomes non-stationary, as the prediction challenge now also requires extrapolation through time. In this context, process-based models for FDCs that mechanistically link the streamflow distribution to climate and landscape factors may have an advantage over purely statistical methods to predict FDCs. This study compares a stochastic (process-based) and statistical method for FDC prediction in both stationary and non-stationary contexts, using Nepal as a case study. Under contemporary conditions, both models perform well in predicting FDCs, with Nash-Sutcliffe coefficients above 0.80 in 75 % of the tested catchments. The main drivers of uncertainty differ between the models: parameter interpolation was the main source of error for the statistical model, while violations of the assumptions of the process-based model represented the main source of its error. The process-based approach performed better than the statistical approach in numerical simulations with non-stationary climate drivers. The predictions of the statistical method under non-stationary rainfall conditions were poor if (i) local runoff coefficients were not accurately determined from the gauge network, or (ii) streamflow variability was strongly affected by changes in rainfall. A Monte Carlo analysis shows that the streamflow regimes in catchments characterized by frequent wet-season runoff and a rapid, strongly non-linear hydrologic response are particularly sensitive to changes in rainfall statistics. In these cases, process-based prediction approaches are favored over statistical models.

Designing Solutions by a Student Centred Approach: Integration of Chemical Process Simulation with Statistical Tools to Improve Distillation Systems

Directory of Open Access Journals (Sweden)

Isabel M. Joao

2017-09-01

Full Text Available Projects thematically focused on simulation and statistical techniques for designing and optimizing chemical processes can be helpful in chemical engineering education in order to meet the needs of engineers. We argue for the relevance of the projects to improve a student centred approach and boost higher order thinking skills. This paper addresses the use of Aspen HYSYS by Portuguese chemical engineering master students to model distillation systems together with statistical experimental design techniques in order to optimize the systems highlighting the value of applying problem specific knowledge, simulation tools and sound statistical techniques. The paper summarizes the work developed by the students in order to model steady-state processes, dynamic processes and optimize the distillation systems emphasizing the benefits of the simulation tools and statistical techniques in helping the students learn how to learn. Students strengthened their domain specific knowledge and became motivated to rethink and improve chemical processes in their future chemical engineering profession. We discuss the main advantages of the methodology from the students’ and teachers perspective

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

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O. Forni

2005-09-01

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

Improved StrongARM latch comparator: Design, analysis and performance evaluation

KAUST Repository

Almansouri, Abdullah Saud Mohammed

2017-07-13

This paper presents an improved StrongARM latch comparator, designed and simulated in 90nm and 32nm CMOS technologies. The proposed design provides an improvement of 7% in energy efficiency, 14% in speed and an average reduction of 41% in the clock feedthrough, compared to the conventional design. The new architecture also minimizes the area by reducing the required transistors needed for the enhanced performance.

Improving Classification of Airborne Laser Scanning Echoes in the Forest-Tundra Ecotone Using Geostatistical and Statistical Measures

Directory of Open Access Journals (Sweden)

Nadja Stumberg

2014-05-01

Full Text Available The vegetation in the forest-tundra ecotone zone is expected to be highly affected by climate change and requires effective monitoring techniques. Airborne laser scanning (ALS has been proposed as a tool for the detection of small pioneer trees for such vast areas using laser height and intensity data. The main objective of the present study was to assess a possible improvement in the performance of classifying tree and nontree laser echoes from high-density ALS data. The data were collected along a 1000 km long transect stretching from southern to northern Norway. Different geostatistical and statistical measures derived from laser height and intensity values were used to extent and potentially improve more simple models ignoring the spatial context. Generalised linear models (GLM and support vector machines (SVM were employed as classification methods. Total accuracies and Cohen’s kappa coefficients were calculated and compared to those of simpler models from a previous study. For both classification methods, all models revealed total accuracies similar to the results of the simpler models. Concerning classification performance, however, the comparison of the kappa coefficients indicated a significant improvement for some models both using GLM and SVM, with classification accuracies >94%.

Measurement Matters: Comparing Old and New Definitions of Rape in Federal Statistical Reporting.

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Bierie, David M; Davis-Siegel, James C

2015-10-01

National statistics on the incidence of rape play an important role in the work of policymakers and academics. The Uniform Crime Reports (UCR) have provided some of the most widely used and influential statistics on the incidence of rape across the United States over the past 80 years. The definition of rape used by UCR changed in 2012 to include substantially more types of sexual assault. This article draws on 20 years of data from the National Incident-Based Reporting System to describe the impact this definitional change will have on estimates of the incidence of rape and trends over time. Drawing on time series as well as panel random effects methodologies, we show that 40% of sexual assaults have been excluded by the prior definition and that the magnitude of this error has grown over time. However, the overall trend in rape over time (year-to-year change) was not substantially different when comparing events meeting the prior definition and the subgroups of sexual assault that will now be counted. © The Author(s) 2014.

Improving Quality in Teaching Statistics Concepts Using Modern Visualization: The Design and Use of the Flash Application on Pocket PCs

Science.gov (United States)

Vaughn, Brandon K.; Wang, Pei-Yu

2009-01-01

The emergence of technology has led to numerous changes in mathematical and statistical teaching and learning which has improved the quality of instruction and teacher/student interactions. The teaching of statistics, for example, has shifted from mathematical calculations to higher level cognitive abilities such as reasoning, interpretation, and…

Independent assessment to continue improvement: Implementing statistical process control at the Hanford Site

International Nuclear Information System (INIS)

Hu, T.A.; Lo, J.C.

1994-11-01

A Quality Assurance independent assessment has brought about continued improvement in the PUREX Plant surveillance program at the Department of Energy's Hanford Site. After the independent assessment, Quality Assurance personnel were closely involved in improving the surveillance program, specifically regarding storage tank monitoring. The independent assessment activities included reviewing procedures, analyzing surveillance data, conducting personnel interviews, and communicating with management. Process improvement efforts included: (1) designing data collection methods; (2) gaining concurrence between engineering and management, (3) revising procedures; and (4) interfacing with shift surveillance crews. Through this process, Statistical Process Control (SPC) was successfully implemented and surveillance management was improved. The independent assessment identified several deficiencies within the surveillance system. These deficiencies can be grouped into two areas: (1) data recording and analysis and (2) handling off-normal conditions. By using several independent assessment techniques, Quality Assurance was able to point out program weakness to senior management and present suggestions for improvements. SPC charting, as implemented by Quality Assurance, is an excellent tool for diagnosing the process, improving communication between the team members, and providing a scientific database for management decisions. In addition, the surveillance procedure was substantially revised. The goals of this revision were to (1) strengthen the role of surveillance management, engineering and operators and (2) emphasize the importance of teamwork for each individual who performs a task. In this instance we believe that the value independent assessment adds to the system is the continuous improvement activities that follow the independent assessment. Excellence in teamwork between the independent assessment organization and the auditee is the key to continuing improvement

Computer-Based Learning: The Use of SPSS Statistical Program for Improving Biostatistical Competence of Medical Students

Directory of Open Access Journals (Sweden)

Zvi H. Perry

2014-01-01

Full Text Available Background. We changed the biostatistics curriculum for our medical students and have created a course entitled “Multivariate analysis of statistical data, using the SPSS package.” Purposes. The aim of this course was to develop students’ skills in computerized data analysis, as well as enhancing their ability to read and interpret statistical data analysis in the literature. Methods. In the current study we have shown that a computer-based course for biostatistics and advanced data analysis is feasible and efficient, using course specific evaluation questionnaires. Results. Its efficacy is both subjective (our subjects felt better prepared to do their theses, as well as to read articles with advanced statistical data analysis and objective (their knowledge of how and when to apply statistical procedures seemed to improve. Conclusions. We showed that a formal evaluative process for such a course is possible and that it enhances the learning experience both for the students and their teachers. In the current study we have shown that a computer-based course for biostatistics and advanced data analysis is feasible and efficient.

Comparative analysis of insect succession data from Victoria (Australia) using summary statistics versus preceding mean ambient temperature models.

Science.gov (United States)

Archer, Mel

2014-03-01

Minimum postmortem interval (mPMI) can be estimated with preceding mean ambient temperature models that predict carrion taxon pre-appearance interval. But accuracy has not been compared with using summary statistics (mean ± SD of taxon arrival/departure day, range, 95% CI). This study collected succession data from ten experimental and five control (infrequently sampled) pig carcasses over two summers (n = 2 experimental, n = 1 control per placement date). Linear and exponential preceding mean ambient temperature models for appearance and departure times were constructed for 17 taxa/developmental stages. There was minimal difference in linear or exponential model success, although arrival models were more often significant: 65% of linear arrival (r2 = 0.09–0.79) and exponential arrival models (r2 = 0.05–81.0) were significant, and 35% of linear departure (r2 = 0.0–0.71) and exponential departure models (r2 = 0.0–0.72) were significant. Performance of models and summary statistics for estimating mPMI was compared in two forensic cases. Only summary statistics produced accurate mPMI estimates.

Studying Student Benefits of Assigning a Service-Learning Project Compared to a Traditional Final Project in a Business Statistics Class

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Phelps, Amy L.; Dostilio, Lina

2008-01-01

The present study addresses the efficacy of using service-learning methods to meet the GAISE guidelines (http://www.amstat.org/education/gaise/GAISECollege.htm) in a second business statistics course and further explores potential advantages of assigning a service-learning (SL) project as compared to the traditional statistics project assignment.…

Forecasting experiments of a dynamical-statistical model of the sea surface temperature anomaly field based on the improved self-memorization principle

Science.gov (United States)

Hong, Mei; Chen, Xi; Zhang, Ren; Wang, Dong; Shen, Shuanghe; Singh, Vijay P.

2018-04-01

With the objective of tackling the problem of inaccurate long-term El Niño-Southern Oscillation (ENSO) forecasts, this paper develops a new dynamical-statistical forecast model of the sea surface temperature anomaly (SSTA) field. To avoid single initial prediction values, a self-memorization principle is introduced to improve the dynamical reconstruction model, thus making the model more appropriate for describing such chaotic systems as ENSO events. The improved dynamical-statistical model of the SSTA field is used to predict SSTA in the equatorial eastern Pacific and during El Niño and La Niña events. The long-term step-by-step forecast results and cross-validated retroactive hindcast results of time series T1 and T2 are found to be satisfactory, with a Pearson correlation coefficient of approximately 0.80 and a mean absolute percentage error (MAPE) of less than 15 %. The corresponding forecast SSTA field is accurate in that not only is the forecast shape similar to the actual field but also the contour lines are essentially the same. This model can also be used to forecast the ENSO index. The temporal correlation coefficient is 0.8062, and the MAPE value of 19.55 % is small. The difference between forecast results in spring and those in autumn is not high, indicating that the improved model can overcome the spring predictability barrier to some extent. Compared with six mature models published previously, the present model has an advantage in prediction precision and length, and is a novel exploration of the ENSO forecast method.

Combining super-ensembles and statistical emulation to improve a regional climate and vegetation model

Science.gov (United States)

Hawkins, L. R.; Rupp, D. E.; Li, S.; Sarah, S.; McNeall, D. J.; Mote, P.; Betts, R. A.; Wallom, D.

2017-12-01

Changing regional patterns of surface temperature, precipitation, and humidity may cause ecosystem-scale changes in vegetation, altering the distribution of trees, shrubs, and grasses. A changing vegetation distribution, in turn, alters the albedo, latent heat flux, and carbon exchanged with the atmosphere with resulting feedbacks onto the regional climate. However, a wide range of earth-system processes that affect the carbon, energy, and hydrologic cycles occur at sub grid scales in climate models and must be parameterized. The appropriate parameter values in such parameterizations are often poorly constrained, leading to uncertainty in predictions of how the ecosystem will respond to changes in forcing. To better understand the sensitivity of regional climate to parameter selection and to improve regional climate and vegetation simulations, we used a large perturbed physics ensemble and a suite of statistical emulators. We dynamically downscaled a super-ensemble (multiple parameter sets and multiple initial conditions) of global climate simulations using a 25-km resolution regional climate model HadRM3p with the land-surface scheme MOSES2 and dynamic vegetation module TRIFFID. We simultaneously perturbed land surface parameters relating to the exchange of carbon, water, and energy between the land surface and atmosphere in a large super-ensemble of regional climate simulations over the western US. Statistical emulation was used as a computationally cost-effective tool to explore uncertainties in interactions. Regions of parameter space that did not satisfy observational constraints were eliminated and an ensemble of parameter sets that reduce regional biases and span a range of plausible interactions among earth system processes were selected. This study demonstrated that by combining super-ensemble simulations with statistical emulation, simulations of regional climate could be improved while simultaneously accounting for a range of plausible land

Using statistical correlation to compare geomagnetic data sets

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Stanton, T.

2009-04-01

The major features of data curves are often matched, to a first order, by bump and wiggle matching to arrive at an offset between data sets. This poster describes a simple statistical correlation program that has proved useful during this stage by determining the optimal correlation between geomagnetic curves using a variety of fixed and floating windows. Its utility is suggested by the fact that it is simple to run, yet generates meaningful data comparisons, often when data noise precludes the obvious matching of curve features. Data sets can be scaled, smoothed, normalised and standardised, before all possible correlations are carried out between selected overlapping portions of each curve. Best-fit offset curves can then be displayed graphically. The program was used to cross-correlate directional and palaeointensity data from Holocene lake sediments (Stanton et al., submitted) and Holocene lava flows. Some example curve matches are shown, including some that illustrate the potential of this technique when examining particularly sparse data sets. Stanton, T., Snowball, I., Zillén, L. and Wastegård, S., submitted. Detecting potential errors in varve chronology and 14C ages using palaeosecular variation curves, lead pollution history and statistical correlation. Quaternary Geochronology.

Fault diagnosis and comparing risk for the steel coil manufacturing process using statistical models for binary data

International Nuclear Information System (INIS)

Debón, A.; Carlos Garcia-Díaz, J.

2012-01-01

Advanced statistical models can help industry to design more economical and rational investment plans. Fault detection and diagnosis is an important problem in continuous hot dip galvanizing. Increasingly stringent quality requirements in the automotive industry also require ongoing efforts in process control to make processes more robust. Robust methods for estimating the quality of galvanized steel coils are an important tool for the comprehensive monitoring of the performance of the manufacturing process. This study applies different statistical regression models: generalized linear models, generalized additive models and classification trees to estimate the quality of galvanized steel coils on the basis of short time histories. The data, consisting of 48 galvanized steel coils, was divided into sets of conforming and nonconforming coils. Five variables were selected for monitoring the process: steel strip velocity and four bath temperatures. The present paper reports a comparative evaluation of statistical models for binary data using Receiver Operating Characteristic (ROC) curves. A ROC curve is a graph or a technique for visualizing, organizing and selecting classifiers based on their performance. The purpose of this paper is to examine their use in research to obtain the best model to predict defective steel coil probability. In relation to the work of other authors who only propose goodness of fit statistics, we should highlight one distinctive feature of the methodology presented here, which is the possibility of comparing the different models with ROC graphs which are based on model classification performance. Finally, the results are validated by bootstrap procedures.

Image quality improvements using adaptive statistical iterative reconstruction for evaluating chronic myocardial infarction using iodine density images with spectral CT.

Science.gov (United States)

Kishimoto, Junichi; Ohta, Yasutoshi; Kitao, Shinichiro; Watanabe, Tomomi; Ogawa, Toshihide

2018-04-01

Single-source dual-energy CT (ssDECT) allows the reconstruction of iodine density images (IDIs) from projection based computing. We hypothesized that adding adaptive statistical iterative reconstruction (ASiR) could improve image quality. The aim of our study was to evaluate the effect and determine the optimal blend percentages of ASiR for IDI of myocardial late iodine enhancement (LIE) in the evaluation of chronic myocardial infarction using ssDECT. A total of 28 patients underwent cardiac LIE using a ssDECT scanner. IDIs between 0 and 100% of ASiR contributions in 10% increments were reconstructed. The signal-to-noise ratio (SNR) of remote myocardia and the contrast-to-noise ratio (CNR) of infarcted myocardia were measured. Transmural extent of infarction was graded using a 5-point scale. The SNR, CNR, and transmural extent were assessed for each ASiR contribution ratio. The transmural extents were compared with MRI as a reference standard. Compared to 0% ASiR, the use of 20-100% ASiR resulted in a reduction of image noise (p ASiR images, reconstruction with 100% ASiR image showed the highest improvement in SNR (229%; p ASiR above 80% showed the highest ratio (73.7%) of accurate transmural extent classification. In conclusion, ASiR intensity of 80-100% in IDIs can improve image quality without changes in signal and maximizes the accuracy of transmural extent in infarcted myocardium.

Chimney stoves modestly improved indoor air quality measurements compared with traditional open fire stoves: results from a small-scale intervention study in rural Peru.

Science.gov (United States)

Hartinger, S M; Commodore, A A; Hattendorf, J; Lanata, C F; Gil, A I; Verastegui, H; Aguilar-Villalobos, M; Mäusezahl, D; Naeher, L P

2013-08-01

Nearly half of the world's population depends on biomass fuels to meet domestic energy needs, producing high levels of pollutants responsible for substantial morbidity and mortality. We compare carbon monoxide (CO) and particulate matter (PM2.5) exposures and kitchen concentrations in households with study-promoted intervention (OPTIMA-improved stoves and control stoves) in San Marcos Province, Cajamarca Region, Peru. We determined 48-h indoor air concentration levels of CO and PM2.5 in 93 kitchen environments and personal exposure, after OPTIMA-improved stoves had been installed for an average of 7 months. PM2.5 and CO measurements did not differ significantly between OPTIMA-improved stoves and control stoves. Although not statistically significant, a post hoc stratification of OPTIMA-improved stoves by level of performance revealed mean PM2.5 and CO levels of fully functional OPTIMA-improved stoves were 28% lower (n = 20, PM2.5, 136 μg/m(3) 95% CI 54-217) and 45% lower (n = 25, CO, 3.2 ppm, 95% CI 1.5-4.9) in the kitchen environment compared with the control stoves (n = 34, PM2.5, 189 μg/m(3), 95% CI 116-261; n = 44, CO, 5.8 ppm, 95% CI 3.3-8.2). Likewise, although not statistically significant, personal exposures for OPTIMA-improved stoves were 43% and 17% lower for PM2.5 (n = 23) and CO (n = 25), respectively. Stove maintenance and functionality level are factors worthy of consideration for future evaluations of stove interventions. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Improved custom statistics visualization for CA Performance Center data

CERN Document Server

Talevi, Iacopo

2017-01-01

The main goal of my project is to understand and experiment the possibilities that CA Performance Center (CA PC) offers for creating custom applications to display stored information through interesting visual means, such as maps. In particular, I have re-written some of the network statistics web pages in order to fetch data from new statistics modules in CA PC, which has its own API, and stop using the RRD data.

Statistics that learn: can logistic discriminant analysis improve diagnosis in brain SPECT?

International Nuclear Information System (INIS)

Behin-Ain, S.; Barnden, L.; Kwiatek, R.; Del Fante, P.; Casse, R.; Burnet, R.; Chew, G.; Kitchener, M.; Boundy, K.; Unger, S.

2002-01-01

Full text: Logistic discriminant analysis (LDA) is a statistical technique capable of discriminating individuals within a diseased group against normals. It also enables classification of various diseases within a group of patients. This technique provides a quantitative, automated and non-subjective clinical diagnostic tool. Based on a population known to have the disease and a normal control group, an algorithm was developed and trained to identify regions in the human brain responsible for the disease in question. The algorithm outputs a statistical map representing diseased or normal probability on a voxel or cluster basis from which an index is generated for each subject. The algorithm also generates a set of coefficients which is used to generate an index for the purpose of classification of new subjects. The results are comparable and complement those of Statistical Parametric Mapping (SPM) which employs a more common linear discriminant technique. The results are presented for brain SPECT studies of two diseases: chronic fatigue syndrome (CFS) and fibromyalgia (FM). A 100% specificity and 94% sensitivity is achieved for the CFS study (similar to SPM results) and for the FM study 82% specificity and 94% sensitivity is achieved with corresponding SPM results showing 90% specificity and 82% sensitivity. The results encourages application of LDA for discrimination of new single subjects as well as of diseased and normal groups. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc

Statistical method to compare massive parallel sequencing pipelines.

Science.gov (United States)

Elsensohn, M H; Leblay, N; Dimassi, S; Campan-Fournier, A; Labalme, A; Roucher-Boulez, F; Sanlaville, D; Lesca, G; Bardel, C; Roy, P

2017-03-01

Today, sequencing is frequently carried out by Massive Parallel Sequencing (MPS) that cuts drastically sequencing time and expenses. Nevertheless, Sanger sequencing remains the main validation method to confirm the presence of variants. The analysis of MPS data involves the development of several bioinformatic tools, academic or commercial. We present here a statistical method to compare MPS pipelines and test it in a comparison between an academic (BWA-GATK) and a commercial pipeline (TMAP-NextGENe®), with and without reference to a gold standard (here, Sanger sequencing), on a panel of 41 genes in 43 epileptic patients. This method used the number of variants to fit log-linear models for pairwise agreements between pipelines. To assess the heterogeneity of the margins and the odds ratios of agreement, four log-linear models were used: a full model, a homogeneous-margin model, a model with single odds ratio for all patients, and a model with single intercept. Then a log-linear mixed model was fitted considering the biological variability as a random effect. Among the 390,339 base-pairs sequenced, TMAP-NextGENe® and BWA-GATK found, on average, 2253.49 and 1857.14 variants (single nucleotide variants and indels), respectively. Against the gold standard, the pipelines had similar sensitivities (63.47% vs. 63.42%) and close but significantly different specificities (99.57% vs. 99.65%; p < 0.001). Same-trend results were obtained when only single nucleotide variants were considered (99.98% specificity and 76.81% sensitivity for both pipelines). The method allows thus pipeline comparison and selection. It is generalizable to all types of MPS data and all pipelines.

Initiating statistical process control to improve quality outcomes in colorectal surgery.

Science.gov (United States)

Keller, Deborah S; Stulberg, Jonah J; Lawrence, Justin K; Samia, Hoda; Delaney, Conor P

2015-12-01

Unexpected variations in postoperative length of stay (LOS) negatively impact resources and patient outcomes. Statistical process control (SPC) measures performance, evaluates productivity, and modifies processes for optimal performance. The goal of this study was to initiate SPC to identify LOS outliers and evaluate its feasibility to improve outcomes in colorectal surgery. Review of a prospective database identified colorectal procedures performed by a single surgeon. Patients were grouped into elective and emergent categories and then stratified by laparoscopic and open approaches. All followed a standardized enhanced recovery protocol. SPC was applied to identify outliers and evaluate causes within each group. A total of 1294 cases were analyzed--83% elective (n = 1074) and 17% emergent (n = 220). Emergent cases were 70.5% open and 29.5% laparoscopic; elective cases were 36.8% open and 63.2% laparoscopic. All groups had a wide range in LOS. LOS outliers ranged from 8.6% (elective laparoscopic) to 10.8% (emergent laparoscopic). Evaluation of outliers demonstrated patient characteristics of higher ASA scores, longer operating times, ICU requirement, and temporary nursing at discharge. Outliers had higher postoperative complication rates in elective open (57.1 vs. 20.0%) and elective lap groups (77.6 vs. 26.1%). Outliers also had higher readmission rates for emergent open (11.4 vs. 5.4%), emergent lap (14.3 vs. 9.2%), and elective lap (32.8 vs. 6.9%). Elective open outliers did not follow trends of longer LOS or higher reoperation rates. SPC is feasible and promising for improving colorectal surgery outcomes. SPC identified patient and process characteristics associated with increased LOS. SPC may allow real-time outlier identification, during quality improvement efforts, and reevaluation of outcomes after introducing process change. SPC has clinical implications for improving patient outcomes and resource utilization.

Improved statistical power with a sparse shape model in detecting an aging effect in the hippocampus and amygdala

Science.gov (United States)

Chung, Moo K.; Kim, Seung-Goo; Schaefer, Stacey M.; van Reekum, Carien M.; Peschke-Schmitz, Lara; Sutterer, Matthew J.; Davidson, Richard J.

2014-03-01

The sparse regression framework has been widely used in medical image processing and analysis. However, it has been rarely used in anatomical studies. We present a sparse shape modeling framework using the Laplace- Beltrami (LB) eigenfunctions of the underlying shape and show its improvement of statistical power. Tradition- ally, the LB-eigenfunctions are used as a basis for intrinsically representing surface shapes as a form of Fourier descriptors. To reduce high frequency noise, only the first few terms are used in the expansion and higher frequency terms are simply thrown away. However, some lower frequency terms may not necessarily contribute significantly in reconstructing the surfaces. Motivated by this idea, we present a LB-based method to filter out only the significant eigenfunctions by imposing a sparse penalty. For dense anatomical data such as deformation fields on a surface mesh, the sparse regression behaves like a smoothing process, which will reduce the error of incorrectly detecting false negatives. Hence the statistical power improves. The sparse shape model is then applied in investigating the influence of age on amygdala and hippocampus shapes in the normal population. The advantage of the LB sparse framework is demonstrated by showing the increased statistical power.

Improving statistical reasoning: theoretical models and practical implications

National Research Council Canada - National Science Library

Sedlmeier, Peter

1999-01-01

... in Psychology? 206 References 216 Author Index 230 Subject Index 235 v PrefacePreface Statistical literacy, the art of drawing reasonable inferences from an abundance of numbers provided daily by...

Statistical improvements in functional magnetic resonance imaging analyses produced by censoring high-motion data points.

Science.gov (United States)

Siegel, Joshua S; Power, Jonathan D; Dubis, Joseph W; Vogel, Alecia C; Church, Jessica A; Schlaggar, Bradley L; Petersen, Steven E

2014-05-01

Subject motion degrades the quality of task functional magnetic resonance imaging (fMRI) data. Here, we test two classes of methods to counteract the effects of motion in task fMRI data: (1) a variety of motion regressions and (2) motion censoring ("motion scrubbing"). In motion regression, various regressors based on realignment estimates were included as nuisance regressors in general linear model (GLM) estimation. In motion censoring, volumes in which head motion exceeded a threshold were withheld from GLM estimation. The effects of each method were explored in several task fMRI data sets and compared using indicators of data quality and signal-to-noise ratio. Motion censoring decreased variance in parameter estimates within- and across-subjects, reduced residual error in GLM estimation, and increased the magnitude of statistical effects. Motion censoring performed better than all forms of motion regression and also performed well across a variety of parameter spaces, in GLMs with assumed or unassumed response shapes. We conclude that motion censoring improves the quality of task fMRI data and can be a valuable processing step in studies involving populations with even mild amounts of head movement. Copyright © 2013 Wiley Periodicals, Inc.

Statistics Clinic

Science.gov (United States)

Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James

2014-01-01

Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.

Statistical analysis of the factors that influenced the mechanical properties improvement of cassava starch films

Science.gov (United States)

Monteiro, Mayra; Oliveira, Victor; Santos, Francisco; Barros Neto, Eduardo; Silva, Karyn; Silva, Rayane; Henrique, João; Chibério, Abimaelle

2017-08-01

In order to obtain cassava starch films with improved mechanical properties in relation to the synthetic polymer in the packaging production, a complete factorial design 23 was carried out in order to investigate which factor significantly influences the tensile strength of the biofilm. The factors to be investigated were cassava starch, glycerol and modified clay contents. Modified bentonite clay was used as a filling material of the biofilm. Glycerol was the plasticizer used to thermoplastify cassava starch. The factorial analysis suggested a regression model capable of predicting the optimal mechanical property of the cassava starch film from the maximization of the tensile strength. The reliability of the regression model was tested by the correlation established with the experimental data through the following statistical analyse: Pareto graph. The modified clay was the factor of greater statistical significance on the observed response variable, being the factor that contributed most to the improvement of the mechanical property of the starch film. The factorial experiments showed that the interaction of glycerol with both modified clay and cassava starch was significant for the reduction of biofilm ductility. Modified clay and cassava starch contributed to the maximization of biofilm ductility, while glycerol contributed to the minimization.

Application Exercises Improve Transfer of Statistical Knowledge in Real-World Situations

Science.gov (United States)

Daniel, Frances; Braasch, Jason L. G.

2013-01-01

The present research investigated whether real-world application exercises promoted students' abilities to spontaneously transfer statistical knowledge and to recognize the use of statistics in real-world contexts. Over the course of a semester of psychological statistics, two classes completed multiple application exercises designed to mimic…

Statistical means to enhance the comparability of data within a pooled analysis of individual data in neurobehavioral toxicology

DEFF Research Database (Denmark)

Meyer-Baron, Monika; Schäper, Michael; Knapp, Guido

2011-01-01

Meta-analyses of individual participant data (IPD) provide important contributions to toxicological risk assessments. However, comparability of individual data cannot be taken for granted when information from different studies has to be summarized. By means of statistical standardization...

Using Statistical Process Control to Drive Improvement in Neonatal Care: A Practical Introduction to Control Charts.

Science.gov (United States)

Gupta, Munish; Kaplan, Heather C

2017-09-01

Quality improvement (QI) is based on measuring performance over time, and variation in data measured over time must be understood to guide change and make optimal improvements. Common cause variation is natural variation owing to factors inherent to any process; special cause variation is unnatural variation owing to external factors. Statistical process control methods, and particularly control charts, are robust tools for understanding data over time and identifying common and special cause variation. This review provides a practical introduction to the use of control charts in health care QI, with a focus on neonatology. Copyright © 2017 Elsevier Inc. All rights reserved.

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

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

2013-03-01

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

Developments in statistical evaluation of clinical trials

CERN Document Server

Oud, Johan; Ghidey, Wendimagegn

2014-01-01

This book describes various ways of approaching and interpreting the data produced by clinical trial studies, with a special emphasis on the essential role that biostatistics plays in clinical trials. Over the past few decades the role of statistics in the evaluation and interpretation of clinical data has become of paramount importance. As a result the standards of clinical study design, conduct and interpretation have undergone substantial improvement. The book includes 18 carefully reviewed chapters on recent developments in clinical trials and their statistical evaluation, with each chapter providing one or more examples involving typical data sets, enabling readers to apply the proposed procedures. The chapters employ a uniform style to enhance comparability between the approaches.

An improved Fuzzy Kappa statistic that accounts for spatial autocorrelation

NARCIS (Netherlands)

Hagen - Zanker, A.H.

2009-01-01

The Fuzzy Kappa statistic expresses the agreement between two categorical raster maps. The statistic goes beyond cell-by-cell comparison and gives partial credit to cells based on the categories found in the neighborhood. When matching categories are found at shorter distances the agreement is

Improving Transparency and Replication in Bayesian Statistics : The WAMBS-Checklist

NARCIS (Netherlands)

Depaoli, Sarah; van de Schoot, Rens

2017-01-01

Bayesian statistical methods are slowly creeping into all fields of science and are becoming ever more popular in applied research. Although it is very attractive to use Bayesian statistics, our personal experience has led us to believe that naively applying Bayesian methods can be dangerous for at

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

Science.gov (United States)

Ordonez, Carlos; Chen, Zhibo

2009-09-01

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

Stochastic simulations for the time evolution of systems which obey generalized statistics: fractional exclusion statistics and Gentile's statistics

International Nuclear Information System (INIS)

Nemnes, G A; Anghel, D V

2010-01-01

We present a stochastic method for the simulation of the time evolution in systems which obey generalized statistics, namely fractional exclusion statistics and Gentile's statistics. The transition rates are derived in the framework of canonical ensembles. This approach introduces a tool for describing interacting fermionic and bosonic systems in non-equilibrium as ideal FES systems, in a computationally efficient manner. The two types of statistics are analyzed comparatively, indicating their intrinsic thermodynamic differences and revealing key aspects related to the species size

Comparative urine analysis by liquid chromatography-mass spectrometry and multivariate statistics : Method development, evaluation, and application to proteinuria

NARCIS (Netherlands)

Kemperman, Ramses F. J.; Horvatovich, Peter L.; Hoekman, Berend; Reijmers, Theo H.; Muskiet, Frits A. J.; Bischoff, Rainer

2007-01-01

We describe a platform for the comparative profiling of urine using reversed-phase liquid chromatography-mass spectrometry (LC-MS) and multivariate statistical data analysis. Urinary compounds were separated by gradient elution and subsequently detected by electrospray Ion-Trap MS. The lower limit

Comparative Statistical Analysis of Gender Equality on the Labour Markets of Romania and EU28

Directory of Open Access Journals (Sweden)

Daniela PAŞNICU

2015-06-01

Full Text Available To achieve the employment target set in the Europe 2020 Strategy is necessary that women's potential and talent to be used optimally. Increasing employment for both men and women is the main way to achieve autonomy, financial independence and poverty reduction. This paper presents a comparative statistical analysis of gender equality on the labour markets of Romania and EU28 based on official statistics records and specific key labour market indicators. The aim was to highlight the gender gap on activity rates, employment rates by age, work time and unemployment rate, including long-term unemployment. The analyses undertaken shows that in the last ten years activity and employment rates of women in Romania had a slightly decreasing trend, while at the EU28 level had an upward trend, which led to the widening gap than the average EU28. The gender gap for the same indicators rose in the period under review, in the case of Romania, while at the EU28 level decreased.

Implementation of a Model Output Statistics based on meteorological variable screening for short‐term wind power forecast

DEFF Research Database (Denmark)

Ranaboldo, Matteo; Giebel, Gregor; Codina, Bernat

2013-01-01

A combination of physical and statistical treatments to post‐process numerical weather predictions (NWP) outputs is needed for successful short‐term wind power forecasts. One of the most promising and effective approaches for statistical treatment is the Model Output Statistics (MOS) technique....... The proposed MOS performed well in both wind farms, and its forecasts compare positively with an actual operative model in use at Risø DTU and other MOS types, showing minimum BIAS and improving NWP power forecast of around 15% in terms of root mean square error. Further improvements could be obtained...

Improvement of Statistical Typhoon Rainfall Forecasting with ANN-Based Southwest Monsoon Enhancement

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Tsung-Yi Pan

2011-01-01

Full Text Available Typhoon Morakot 2009, with significant southwest monsoon flow, produced a record-breaking rainfall of 2361 mm in 48 hours. This study hopes to improve a statistical typhoon rainfall forecasting method used over the mountain region of Taiwan via an artificial neural network based southwest monsoon enhancement (ANNSME model. Rainfall data collected at two mountain weather stations, ALiShan and YuShan, are analyzed to establish the relation to the southwest monsoon moisture flux which is calculated at a designated sea area southwest of Taiwan. The results show that the moisture flux, with southwest monsoon flow, transported water vapor during the landfall periods of Typhoons Mindulle, Bilis, Fungwong, Kalmaegi, Haitaing and Morakot. Based on the moisture flux, a linear regression is used to identify an effective value of moisture flux as the threshold flux which can enhance mountain rainfall in southwestern Taiwan. In particular, a feedforward neural network (FNN is applied to estimate the residuals from the linear model to the differences between simulated rainfalls by a typhoon rainfall climatology model (TRCM and observations. Consequently, the ANNSME model integrates the effective moisture flux, linear rainfall model and the FNN for residuals. Even with very limited training cases, our results indicate that the ANNSME model is robust and suitable for improvement of TRCM rainfall prediction. The improved prediction of the total rainfall and of the multiple rainfall peaks is important for emergency operation.

Optimal choice of word length when comparing two Markov sequences using a χ 2-statistic.

Science.gov (United States)

Bai, Xin; Tang, Kujin; Ren, Jie; Waterman, Michael; Sun, Fengzhu

2017-10-03

Alignment-free sequence comparison using counts of word patterns (grams, k-tuples) has become an active research topic due to the large amount of sequence data from the new sequencing technologies. Genome sequences are frequently modelled by Markov chains and the likelihood ratio test or the corresponding approximate χ 2 -statistic has been suggested to compare two sequences. However, it is not known how to best choose the word length k in such studies. We develop an optimal strategy to choose k by maximizing the statistical power of detecting differences between two sequences. Let the orders of the Markov chains for the two sequences be r 1 and r 2 , respectively. We show through both simulations and theoretical studies that the optimal k= max(r 1 ,r 2 )+1 for both long sequences and next generation sequencing (NGS) read data. The orders of the Markov chains may be unknown and several methods have been developed to estimate the orders of Markov chains based on both long sequences and NGS reads. We study the power loss of the statistics when the estimated orders are used. It is shown that the power loss is minimal for some of the estimators of the orders of Markov chains. Our studies provide guidelines on choosing the optimal word length for the comparison of Markov sequences.

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

DEFF Research Database (Denmark)

Zhai, Weiwei; Nielsen, Rasmus; Slatkin, Montgomery

2009-01-01

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

Adaptive Statistical Iterative Reconstruction-Applied Ultra-Low-Dose CT with Radiography-Comparable Radiation Dose: Usefulness for Lung Nodule Detection.

Science.gov (United States)

Yoon, Hyun Jung; Chung, Myung Jin; Hwang, Hye Sun; Moon, Jung Won; Lee, Kyung Soo

2015-01-01

To assess the performance of adaptive statistical iterative reconstruction (ASIR)-applied ultra-low-dose CT (ULDCT) in detecting small lung nodules. Thirty patients underwent both ULDCT and standard dose CT (SCT). After determining the reference standard nodules, five observers, blinded to the reference standard reading results, independently evaluated SCT and both subsets of ASIR- and filtered back projection (FBP)-driven ULDCT images. Data assessed by observers were compared statistically. Converted effective doses in SCT and ULDCT were 2.81 ± 0.92 and 0.17 ± 0.02 mSv, respectively. A total of 114 lung nodules were detected on SCT as a standard reference. There was no statistically significant difference in sensitivity between ASIR-driven ULDCT and SCT for three out of the five observers (p = 0.678, 0.735, ASIR-driven ULDCT in three out of the five observers (p ASIR-driven ULDCT, and SCT were 0.682, 0.772, and 0.821, respectively, and there were no significant differences in FOM values between ASIR-driven ULDCT and SCT (p = 0.11), but the FOM value of FBP-driven ULDCT was significantly lower than that of ASIR-driven ULDCT and SCT (p = 0.01 and 0.00). Adaptive statistical iterative reconstruction-driven ULDCT delivering a radiation dose of only 0.17 mSv offers acceptable sensitivity in nodule detection compared with SCT and has better performance than FBP-driven ULDCT.

Kappa statistic for clustered matched-pair data.

Science.gov (United States)

Yang, Zhao; Zhou, Ming

2014-07-10

Kappa statistic is widely used to assess the agreement between two procedures in the independent matched-pair data. For matched-pair data collected in clusters, on the basis of the delta method and sampling techniques, we propose a nonparametric variance estimator for the kappa statistic without within-cluster correlation structure or distributional assumptions. The results of an extensive Monte Carlo simulation study demonstrate that the proposed kappa statistic provides consistent estimation and the proposed variance estimator behaves reasonably well for at least a moderately large number of clusters (e.g., K ≥50). Compared with the variance estimator ignoring dependence within a cluster, the proposed variance estimator performs better in maintaining the nominal coverage probability when the intra-cluster correlation is fair (ρ ≥0.3), with more pronounced improvement when ρ is further increased. To illustrate the practical application of the proposed estimator, we analyze two real data examples of clustered matched-pair data. Copyright © 2014 John Wiley & Sons, Ltd.

COMPARATIVE EFFECT OF STATIC AND DYNAMIC STRETCHING EXERCISE TO IMPROVE FLEXIBILITY OF HAMSTRING MUSCLES AMONG NON ATHLETES

Directory of Open Access Journals (Sweden)

Jibi Paul

2014-10-01

Full Text Available Background: Stretching exercises have been routinely used in persons with hamstring tightness and athletes to increase flexibility of muscle and to reduce joint injuries. Many studies have reported effect of static and dynamic stretching on flexibility of this muscle. Finding the best method to improve flexibility of hamstring muscle is important for athletes and individuals to reduce their injuries. Objective of the study was to find out the effect of static stretching exercise and dynamic stretching exercise on flexibility of hamstring muscle and also to compare the effect of static and dynamic stretching exercise on flexibility of hamstring muscle. Methods: This was a comparative experimental study with seventy four female healthy subjects from physiotherapy department of KPJ Healthcare University College, Malaysia. Convenient sampling method used to select the samples. The subjects were selected by inclusion criteria and randomly divided equally in to two with 37 subjects in each group. Static stretching exercise and dynamic stretching exercise were given as intervention program for four weeks respectively for experimental and control group. Pre and post data of restricted range of movement for knee extension was measured using goniometry and documented separately for both group. Result: In experimental and control group, pre-post statistical analysis found significant effect in increase of hamstring flexibility with P<0.0001, for right and left side. Comparative study between experimental and control group found that static stretching exercise have significant effect in increase of hamstring flexibility for right and left side with P<0.04. Conclusion: This study concluded that static stretching exercise is more effective to improve hamstring flexibility compared to dynamic stretching exercise.

Improved Statistical Fault Detection Technique and Application to Biological Phenomena Modeled by S-Systems.

Science.gov (United States)

Mansouri, Majdi; Nounou, Mohamed N; Nounou, Hazem N

2017-09-01

In our previous work, we have demonstrated the effectiveness of the linear multiscale principal component analysis (PCA)-based moving window (MW)-generalized likelihood ratio test (GLRT) technique over the classical PCA and multiscale principal component analysis (MSPCA)-based GLRT methods. The developed fault detection algorithm provided optimal properties by maximizing the detection probability for a particular false alarm rate (FAR) with different values of windows, and however, most real systems are nonlinear, which make the linear PCA method not able to tackle the issue of non-linearity to a great extent. Thus, in this paper, first, we apply a nonlinear PCA to obtain an accurate principal component of a set of data and handle a wide range of nonlinearities using the kernel principal component analysis (KPCA) model. The KPCA is among the most popular nonlinear statistical methods. Second, we extend the MW-GLRT technique to one that utilizes exponential weights to residuals in the moving window (instead of equal weightage) as it might be able to further improve fault detection performance by reducing the FAR using exponentially weighed moving average (EWMA). The developed detection method, which is called EWMA-GLRT, provides improved properties, such as smaller missed detection and FARs and smaller average run length. The idea behind the developed EWMA-GLRT is to compute a new GLRT statistic that integrates current and previous data information in a decreasing exponential fashion giving more weight to the more recent data. This provides a more accurate estimation of the GLRT statistic and provides a stronger memory that will enable better decision making with respect to fault detection. Therefore, in this paper, a KPCA-based EWMA-GLRT method is developed and utilized in practice to improve fault detection in biological phenomena modeled by S-systems and to enhance monitoring process mean. The idea behind a KPCA-based EWMA-GLRT fault detection algorithm is to

A tale of two audits: statistical process control for improving diabetes care in primary care settings.

Science.gov (United States)

Al-Hussein, Fahad Abdullah

2008-01-01

Diabetes constitutes a major burden of disease globally. Both primary and secondary prevention need to improve in order to face this challenge. Improving management of diabetes in primary care is therefore of fundamental importance. The objective of these series of audits was to find means of improving diabetes management in chronic disease mini-clinics in primary health care. In the process, we were able to study the effect and practical usefulness of different audit designs - those measuring clinical outcomes, process of care, or both. King Saud City Family and Community Medicine Centre, Saudi National Guard Health Affairs in Riyadh city, Saudi Arabia. Simple random samples of 30 files were selected every two weeks from a sampling frame of file numbers for all diabetes clients seen over the period. Information was transferred to a form, entered on the computer and an automated response was generated regarding the appropriateness of management, a criterion mutually agreed upon by care providers. The results were plotted on statistical process control charts, p charts, displayed for all employees. Data extraction, archiving, entry, analysis, plotting and design and preparation of p charts were managed by nursing staff specially trained for the purpose by physicians with relevant previous experience. Audit series with mixed outcome and process measures failed to detect any changes in the proportion of non-conforming cases over a period of one year. The process measures series, on the other hand, showed improvement in care corresponding to a reduction in the proportion non-conforming by 10% within a period of 3 months. Non-conformities dropped from a mean of 5.0 to 1.4 over the year (P process audits and feedbacks. Frequent process audits in the context of statistical process control should be supplemented with concurrent outcome audits, once or twice a year.

Statistically optimal estimation of Greenland Ice Sheet mass variations from GRACE monthly solutions using an improved mascon approach

Science.gov (United States)

Ran, J.; Ditmar, P.; Klees, R.; Farahani, H. H.

2018-03-01

We present an improved mascon approach to transform monthly spherical harmonic solutions based on GRACE satellite data into mass anomaly estimates in Greenland. The GRACE-based spherical harmonic coefficients are used to synthesize gravity anomalies at satellite altitude, which are then inverted into mass anomalies per mascon. The limited spectral content of the gravity anomalies is properly accounted for by applying a low-pass filter as part of the inversion procedure to make the functional model spectrally consistent with the data. The full error covariance matrices of the monthly GRACE solutions are properly propagated using the law of covariance propagation. Using numerical experiments, we demonstrate the importance of a proper data weighting and of the spectral consistency between functional model and data. The developed methodology is applied to process real GRACE level-2 data (CSR RL05). The obtained mass anomaly estimates are integrated over five drainage systems, as well as over entire Greenland. We find that the statistically optimal data weighting reduces random noise by 35-69%, depending on the drainage system. The obtained mass anomaly time-series are de-trended to eliminate the contribution of ice discharge and are compared with de-trended surface mass balance (SMB) time-series computed with the Regional Atmospheric Climate Model (RACMO 2.3). We show that when using a statistically optimal data weighting in GRACE data processing, the discrepancies between GRACE-based estimates of SMB and modelled SMB are reduced by 24-47%.

QUALITY IMPROVEMENT USING STATISTICAL PROCESS CONTROL TOOLS IN GLASS BOTTLES MANUFACTURING COMPANY

Directory of Open Access Journals (Sweden)

Yonatan Mengesha Awaj

2013-03-01

Full Text Available In order to survive in a competitive market, improving quality and productivity of product or process is a must for any company. This study is about to apply the statistical process control (SPC tools in the production processing line and on final product in order to reduce defects by identifying where the highest waste is occur at and to give suggestion for improvement. The approach used in this study is direct observation, thorough examination of production process lines, brain storming session, fishbone diagram, and information has been collected from potential customers and company's workers through interview and questionnaire, Pareto chart/analysis and control chart (p-chart was constructed. It has been found that the company has many problems; specifically there is high rejection or waste in the production processing line. The highest waste occurs in melting process line which causes loss due to trickle and in the forming process line which causes loss due to defective product rejection. The vital few problems were identified, it was found that the blisters, double seam, stone, pressure failure and overweight are the vital few problems. The principal aim of the study is to create awareness to quality team how to use SPC tools in the problem analysis, especially to train quality team on how to held an effective brainstorming session, and exploit these data in cause-and-effect diagram construction, Pareto analysis and control chart construction. The major causes of non-conformities and root causes of the quality problems were specified, and possible remedies were proposed. Although the company has many constraints to implement all suggestion for improvement within short period of time, the company recognized that the suggestion will provide significant productivity improvement in the long run.

Narrative Review of Statistical Reporting Checklists, Mandatory Statistical Editing, and Rectifying Common Problems in the Reporting of Scientific Articles.

Science.gov (United States)

Dexter, Franklin; Shafer, Steven L

2017-03-01

Considerable attention has been drawn to poor reproducibility in the biomedical literature. One explanation is inadequate reporting of statistical methods by authors and inadequate assessment of statistical reporting and methods during peer review. In this narrative review, we examine scientific studies of several well-publicized efforts to improve statistical reporting. We also review several retrospective assessments of the impact of these efforts. These studies show that instructions to authors and statistical checklists are not sufficient; no findings suggested that either improves the quality of statistical methods and reporting. Second, even basic statistics, such as power analyses, are frequently missing or incorrectly performed. Third, statistical review is needed for all papers that involve data analysis. A consistent finding in the studies was that nonstatistical reviewers (eg, "scientific reviewers") and journal editors generally poorly assess statistical quality. We finish by discussing our experience with statistical review at Anesthesia & Analgesia from 2006 to 2016.

Comparing statistical tests for detecting soil contamination greater than background

International Nuclear Information System (INIS)

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

1993-12-01

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

Using health statistics: a Nightingale legacy.

Science.gov (United States)

Schloman, B F

2001-01-01

No more forceful example of the value of using health statistics to understand and improve health conditions exists than displayed by Florence Nightingale. The recent book by Dossey (1999), Florence Nightingale: Mystic, Visionary, Healer, relates the dramatic tale of Nightingale s use of statistics to understand the causes of deaths in the Crimean War and of her advocacy to standardize the collection of medical data within the army and in civilian hospitals. For her, the use of health statistics was a major tool to improve health and influence public opinion.

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

Science.gov (United States)

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

2015-04-30

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

The application of statistical techniques to nuclear materials accountancy

International Nuclear Information System (INIS)

Annibal, P.S.; Roberts, P.D.

1990-02-01

Over the past decade much theoretical research has been carried out on the development of statistical methods for nuclear materials accountancy. In practice plant operation may differ substantially from the idealized models often cited. This paper demonstrates the importance of taking account of plant operation in applying the statistical techniques, to improve the accuracy of the estimates and the knowledge of the errors. The benefits are quantified either by theoretical calculation or by simulation. Two different aspects are considered; firstly, the use of redundant measurements to reduce the error on the estimate of the mass of heavy metal in an accountancy tank is investigated. Secondly, a means of improving the knowledge of the 'Material Unaccounted For' (the difference between the inventory calculated from input/output data, and the measured inventory), using information about the plant measurement system, is developed and compared with existing general techniques. (author)

Estimation of measurement variance in the context of environment statistics

Science.gov (United States)

Maiti, Pulakesh

2015-02-01

The object of environment statistics is for providing information on the environment, on its most important changes over time, across locations and identifying the main factors that influence them. Ultimately environment statistics would be required to produce higher quality statistical information. For this timely, reliable and comparable data are needed. Lack of proper and uniform definitions, unambiguous classifications pose serious problems to procure qualitative data. These cause measurement errors. We consider the problem of estimating measurement variance so that some measures may be adopted to improve upon the quality of data on environmental goods and services and on value statement in economic terms. The measurement technique considered here is that of employing personal interviewers and the sampling considered here is that of two-stage sampling.

Statistical methods towards more efficient infiltration measurements.

Science.gov (United States)

Franz, T; Krebs, P

2006-01-01

A comprehensive knowledge about the infiltration situation in a catchment is required for operation and maintenance. Due to the high expenditures, an optimisation of necessary measurement campaigns is essential. Methods based on multivariate statistics were developed to improve the information yield of measurements by identifying appropriate gauge locations. The methods have a high degree of freedom against data needs. They were successfully tested on real and artificial data. For suitable catchments, it is estimated that the optimisation potential amounts up to 30% accuracy improvement compared to nonoptimised gauge distributions. Beside this, a correlation between independent reach parameters and dependent infiltration rates could be identified, which is not dominated by the groundwater head.

Improved Statistical Method For Hydrographic Climatic Records Quality Control

Science.gov (United States)

Gourrion, J.; Szekely, T.

2016-02-01

Climate research benefits from the continuous development of global in-situ hydrographic networks in the last decades. Apart from the increasing volume of observations available on a large range of temporal and spatial scales, a critical aspect concerns the ability to constantly improve the quality of the datasets. In the context of the Coriolis Dataset for ReAnalysis (CORA) version 4.2, a new quality control method based on a local comparison to historical extreme values ever observed is developed, implemented and validated. Temperature, salinity and potential density validity intervals are directly estimated from minimum and maximum values from an historical reference dataset, rather than from traditional mean and standard deviation estimates. Such an approach avoids strong statistical assumptions on the data distributions such as unimodality, absence of skewness and spatially homogeneous kurtosis. As a new feature, it also allows addressing simultaneously the two main objectives of a quality control strategy, i.e. maximizing the number of good detections while minimizing the number of false alarms. The reference dataset is presently built from the fusion of 1) all ARGO profiles up to early 2014, 2) 3 historical CTD datasets and 3) the Sea Mammals CTD profiles from the MEOP database. All datasets are extensively and manually quality controlled. In this communication, the latest method validation results are also presented. The method has been implemented in the latest version of the CORA dataset and will benefit to the next version of the Copernicus CMEMS dataset.

Improving statistical accounting as an element of quality management development in healthcare

Directory of Open Access Journals (Sweden)

Gulnara R. Khamidullina

2014-01-01

Full Text Available Objective to offer a solution to the problem of statistical accounting in health care on the basis of stationary medical institutions which will serve as the basis for solving many of the challenges facing the management of health institutions. Method systematic logical analysis was used. Scientific novelty solution to the issues of collecting recording and using statistical indicators necessary for the medical institution functioning is proposed. The possibility is proved of using this approach for solving problems of healthcare management. Practical value the use of research results for the processing of statistical information will reduce the risk of losing information. It will allow health care managers to use both statistical information and data on availability and consumption of materials thus ensuring the timeliness and correctness of managerial decisions. Results the problem of collecting processing and recording statistical information in a stationary medical institution is discussed. On the basis of the conducted research a solution is proposed to the problem of errors in the collecting processing transferring and keeping statistical information in health care. The necessity of these implementations is proved. The economic efficiency is proved which is associated with the timely managerial decisions on the basis of the offered variant of statistical accounting.

A comparative empirical analysis of statistical models for evaluating highway segment crash frequency

Directory of Open Access Journals (Sweden)

Bismark R.D.K. Agbelie

2016-08-01

Full Text Available The present study conducted an empirical highway segment crash frequency analysis on the basis of fixed-parameters negative binomial and random-parameters negative binomial models. Using a 4-year data from a total of 158 highway segments, with a total of 11,168 crashes, the results from both models were presented, discussed, and compared. About 58% of the selected variables produced normally distributed parameters across highway segments, while the remaining produced fixed parameters. The presence of a noise barrier along a highway segment would increase mean annual crash frequency by 0.492 for 88.21% of the highway segments, and would decrease crash frequency for 11.79% of the remaining highway segments. Besides, the number of vertical curves per mile along a segment would increase mean annual crash frequency by 0.006 for 84.13% of the highway segments, and would decrease crash frequency for 15.87% of the remaining highway segments. Thus, constraining the parameters to be fixed across all highway segments would lead to an inaccurate conclusion. Although, the estimated parameters from both models showed consistency in direction, the magnitudes were significantly different. Out of the two models, the random-parameters negative binomial model was found to be statistically superior in evaluating highway segment crashes compared with the fixed-parameters negative binomial model. On average, the marginal effects from the fixed-parameters negative binomial model were observed to be significantly overestimated compared with those from the random-parameters negative binomial model.

Improving Statistics Education through Simulations: The Case of the Sampling Distribution.

Science.gov (United States)

Earley, Mark A.

This paper presents a summary of action research investigating statistics students' understandings of the sampling distribution of the mean. With four sections of an introductory Statistics in Education course (n=98 students), a computer simulation activity (R. delMas, J. Garfield, and B. Chance, 1999) was implemented and evaluated to show…

Do Introductory Statistics Courses in the United States Improve Students' Attitudes?

Science.gov (United States)

Schau, Candace; Emmioglu, Esma

2012-01-01

We examined the attitudes of about 2200 students enrolled in 101 sections of post-secondary introductory statistics service courses located across the United States. Using the "Survey of Attitudes Toward Statistics-36," we assessed students' attitudes when they entered and left their courses, as well as changes in attitudes across their courses.…

Can bias correction and statistical downscaling methods improve the skill of seasonal precipitation forecasts?

Science.gov (United States)

Manzanas, R.; Lucero, A.; Weisheimer, A.; Gutiérrez, J. M.

2018-02-01

Statistical downscaling methods are popular post-processing tools which are widely used in many sectors to adapt the coarse-resolution biased outputs from global climate simulations to the regional-to-local scale typically required by users. They range from simple and pragmatic Bias Correction (BC) methods, which directly adjust the model outputs of interest (e.g. precipitation) according to the available local observations, to more complex Perfect Prognosis (PP) ones, which indirectly derive local predictions (e.g. precipitation) from appropriate upper-air large-scale model variables (predictors). Statistical downscaling methods have been extensively used and critically assessed in climate change applications; however, their advantages and limitations in seasonal forecasting are not well understood yet. In particular, a key problem in this context is whether they serve to improve the forecast quality/skill of raw model outputs beyond the adjustment of their systematic biases. In this paper we analyze this issue by applying two state-of-the-art BC and two PP methods to downscale precipitation from a multimodel seasonal hindcast in a challenging tropical region, the Philippines. To properly assess the potential added value beyond the reduction of model biases, we consider two validation scores which are not sensitive to changes in the mean (correlation and reliability categories). Our results show that, whereas BC methods maintain or worsen the skill of the raw model forecasts, PP methods can yield significant skill improvement (worsening) in cases for which the large-scale predictor variables considered are better (worse) predicted by the model than precipitation. For instance, PP methods are found to increase (decrease) model reliability in nearly 40% of the stations considered in boreal summer (autumn). Therefore, the choice of a convenient downscaling approach (either BC or PP) depends on the region and the season.

Innovations in Statistical Observations of Consumer Prices

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Olga Stepanovna Oleynik

2016-10-01

Full Text Available This article analyzes the innovative changes in the methodology of statistical surveys of consumer prices. These changes are reflected in the “Official statistical methodology for the organization of statistical observation of consumer prices for goods and services and the calculation of the consumer price index”, approved by order of the Federal State Statistics Service of December 30, 2014 no. 734. The essence of innovation is the use of mathematical methods in determining the range of studies objects of trade and services, in calculating the sufficient observable price quotes based on price dispersion, the proportion of the observed product (service, a representative of consumer spending, as well as the indicator of the complexity of price registration. The authors analyzed the mathematical calculations of the required number of quotations for observation in the Volgograd region in 2016, the results of calculations are compared with the number of quotes included in the monitoring. The authors believe that the implementation of these mathematical models allowed to substantially reduce the influence of the subjective factor in the organization of monitoring of consumer prices, and therefore to increase the objectivity of the resulting statistics on consumer prices and inflation. At the same time, the proposed methodology needs further improvement in terms of payment for goods, products (services by representatives having a minor share in consumer expenditure.

STATISTICS IN SERVICE QUALITY ASSESSMENT

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Dragana Gardašević

2012-09-01

Full Text Available For any quality evaluation in sports, science, education, and so, it is useful to collect data to construct a strategy to improve the quality of services offered to the user. For this purpose, we use statistical software packages for data processing data collected in order to increase customer satisfaction. The principle is demonstrated by the example of the level of student satisfaction ratings Belgrade Polytechnic (as users the quality of institutions (Belgrade Polytechnic. Here, the emphasis on statistical analysis as a tool for quality control in order to improve the same, and not the interpretation of results. Therefore, the above can be used as a model in sport to improve the overall results.

Correcting the Count: Improving Vital Statistics Data Regarding Deaths Related to Obesity.

Science.gov (United States)

McCleskey, Brandi C; Davis, Gregory G; Dye, Daniel W

2017-11-15

Obesity can involve any organ system and compromise the overall health of an individual, including premature death. Despite the increased risk of death associated with being obese, obesity itself is infrequently indicated on the death certificate. We performed an audit of our records to identify how often "obesity" was listed on the death certificate to determine how our practices affected national mortality data collection regarding obesity-related mortality. During the span of nearly 25 years, 0.2% of deaths were attributed to or contributed by obesity. Over the course of 5 years, 96% of selected natural deaths were likely underreported as being associated with obesity. We present an algorithm for certifiers to use to determine whether obesity should be listed on the death certificate and guidelines for certifying cases in which this is appropriate. Use of this algorithm will improve vital statistics concerning the role of obesity in causing or contributing to death. © 2017 American Academy of Forensic Sciences.

Improved statistical method for temperature and salinity quality control

Science.gov (United States)

Gourrion, Jérôme; Szekely, Tanguy

2017-04-01

Climate research and Ocean monitoring benefit from the continuous development of global in-situ hydrographic networks in the last decades. Apart from the increasing volume of observations available on a large range of temporal and spatial scales, a critical aspect concerns the ability to constantly improve the quality of the datasets. In the context of the Coriolis Dataset for ReAnalysis (CORA) version 4.2, a new quality control method based on a local comparison to historical extreme values ever observed is developed, implemented and validated. Temperature, salinity and potential density validity intervals are directly estimated from minimum and maximum values from an historical reference dataset, rather than from traditional mean and standard deviation estimates. Such an approach avoids strong statistical assumptions on the data distributions such as unimodality, absence of skewness and spatially homogeneous kurtosis. As a new feature, it also allows addressing simultaneously the two main objectives of an automatic quality control strategy, i.e. maximizing the number of good detections while minimizing the number of false alarms. The reference dataset is presently built from the fusion of 1) all ARGO profiles up to late 2015, 2) 3 historical CTD datasets and 3) the Sea Mammals CTD profiles from the MEOP database. All datasets are extensively and manually quality controlled. In this communication, the latest method validation results are also presented. The method has already been implemented in the latest version of the delayed-time CMEMS in-situ dataset and will be deployed soon in the equivalent near-real time products.

Audiology patient fall statistics and risk factors compared to non-audiology patients.

Science.gov (United States)

Criter, Robin E; Honaker, Julie A

2016-10-01

To compare fall statistics (e.g. incidence, prevalence), fall risks, and characteristics of patients who seek hearing healthcare from an audiologist to individuals who have not sought such services. Case-control study. Two groups of community-dwelling older adult patients: 25 audiology patients aged 60 years or older (M age: 69.2 years, SD: 4.5, range: 61-77) and a control group (gender- and age-matched ±2 years) of 25 non-audiology patients (M age: 69.6, SD: 4.7, range: 60-77). Annual incidence of falls (most recent 12 months) was higher in audiology patients (68.0%) than non-audiology patients (28.0%; p = .005). Audiology patients reported a higher incidence of multiple recent falls (p =.025) and more chronic health conditions (p = .028) than non-audiology patients. Significantly more audiology patients fall on an annual basis than non-audiology patients, suggesting that falls are a pervasive issue in general hearing clinics. Further action on the part of healthcare professionals providing audiologic services may be necessary to identify individuals at risk for falling.

Statistical Dependence of Pipe Breaks on Explanatory Variables

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Patricia Gómez-Martínez

2017-02-01

Full Text Available Aging infrastructure is the main challenge currently faced by water suppliers. Estimation of assets lifetime requires reliable criteria to plan assets repair and renewal strategies. To do so, pipe break prediction is one of the most important inputs. This paper analyzes the statistical dependence of pipe breaks on explanatory variables, determining their optimal combination and quantifying their influence on failure prediction accuracy. A large set of registered data from Madrid water supply network, managed by Canal de Isabel II, has been filtered, classified and studied. Several statistical Bayesian models have been built and validated from the available information with a technique that combines reference periods of time as well as geographical location. Statistical models of increasing complexity are built from zero up to five explanatory variables following two approaches: a set of independent variables or a combination of two joint variables plus an additional number of independent variables. With the aim of finding the variable combination that provides the most accurate prediction, models are compared following an objective validation procedure based on the model skill to predict the number of pipe breaks in a large set of geographical locations. As expected, model performance improves as the number of explanatory variables increases. However, the rate of improvement is not constant. Performance metrics improve significantly up to three variables, but the tendency is softened for higher order models, especially in trunk mains where performance is reduced. Slight differences are found between trunk mains and distribution lines when selecting the most influent variables and models.

Statistical Analyses of High-Resolution Aircraft and Satellite Observations of Sea Ice: Applications for Improving Model Simulations

Science.gov (United States)

Farrell, S. L.; Kurtz, N. T.; Richter-Menge, J.; Harbeck, J. P.; Onana, V.

2012-12-01

Satellite-derived estimates of ice thickness and observations of ice extent over the last decade point to a downward trend in the basin-scale ice volume of the Arctic Ocean. This loss has broad-ranging impacts on the regional climate and ecosystems, as well as implications for regional infrastructure, marine navigation, national security, and resource exploration. New observational datasets at small spatial and temporal scales are now required to improve our understanding of physical processes occurring within the ice pack and advance parameterizations in the next generation of numerical sea-ice models. High-resolution airborne and satellite observations of the sea ice are now available at meter-scale resolution or better that provide new details on the properties and morphology of the ice pack across basin scales. For example the NASA IceBridge airborne campaign routinely surveys the sea ice of the Arctic and Southern Oceans with an advanced sensor suite including laser and radar altimeters and digital cameras that together provide high-resolution measurements of sea ice freeboard, thickness, snow depth and lead distribution. Here we present statistical analyses of the ice pack primarily derived from the following IceBridge instruments: the Digital Mapping System (DMS), a nadir-looking, high-resolution digital camera; the Airborne Topographic Mapper, a scanning lidar; and the University of Kansas snow radar, a novel instrument designed to estimate snow depth on sea ice. Together these instruments provide data from which a wide range of sea ice properties may be derived. We provide statistics on lead distribution and spacing, lead width and area, floe size and distance between floes, as well as ridge height, frequency and distribution. The goals of this study are to (i) identify unique statistics that can be used to describe the characteristics of specific ice regions, for example first-year/multi-year ice, diffuse ice edge/consolidated ice pack, and convergent

Improved estimation of the noncentrality parameter distribution from a large number of t-statistics, with applications to false discovery rate estimation in microarray data analysis.

Science.gov (United States)

Qu, Long; Nettleton, Dan; Dekkers, Jack C M

2012-12-01

Given a large number of t-statistics, we consider the problem of approximating the distribution of noncentrality parameters (NCPs) by a continuous density. This problem is closely related to the control of false discovery rates (FDR) in massive hypothesis testing applications, e.g., microarray gene expression analysis. Our methodology is similar to, but improves upon, the existing approach by Ruppert, Nettleton, and Hwang (2007, Biometrics, 63, 483-495). We provide parametric, nonparametric, and semiparametric estimators for the distribution of NCPs, as well as estimates of the FDR and local FDR. In the parametric situation, we assume that the NCPs follow a distribution that leads to an analytically available marginal distribution for the test statistics. In the nonparametric situation, we use convex combinations of basis density functions to estimate the density of the NCPs. A sequential quadratic programming procedure is developed to maximize the penalized likelihood. The smoothing parameter is selected with the approximate network information criterion. A semiparametric estimator is also developed to combine both parametric and nonparametric fits. Simulations show that, under a variety of situations, our density estimates are closer to the underlying truth and our FDR estimates are improved compared with alternative methods. Data-based simulations and the analyses of two microarray datasets are used to evaluate the performance in realistic situations. © 2012, The International Biometric Society.

Silicon Photomultipliers: Dark Current and its Statistical Spread

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Roberto PAGANO

2012-03-01

Full Text Available Aim of this paper is to investigate on a statistical basis at the wafer level the relationship existing among the dark currents of the single pixel compared to the whole Silicon Photomultiplier array. This is the first time to our knowledge that such a comparison is made, crucial to pass this new technology to the semiconductor manufacturing standards. In particular, emission microscopy measurements and current measurements allowed us to conclude that optical trenches strongly improve the device performances.

Adaptive statistical iterative reconstruction-applied ultra-low-dose CT with radiography- comparable radiation dose: Usefulness for lung nodule detection

International Nuclear Information System (INIS)

Yoon, Hyun Jung; Chung, Myung Jin; Hwang, Hye Sun; Lee, Kyung Soo; Moon, Jung Won

2015-01-01

To assess the performance of adaptive statistical iterative reconstruction (ASIR)-applied ultra-low-dose CT (ULDCT) in detecting small lung nodules. Thirty patients underwent both ULDCT and standard dose CT (SCT). After determining the reference standard nodules, five observers, blinded to the reference standard reading results, independently evaluated SCT and both subsets of ASIR- and filtered back projection (FBP)-driven ULDCT images. Data assessed by observers were compared statistically. Converted effective doses in SCT and ULDCT were 2.81 ± 0.92 and 0.17 ± 0.02 mSv, respectively. A total of 114 lung nodules were detected on SCT as a standard reference. There was no statistically significant difference in sensitivity between ASIR-driven ULDCT and SCT for three out of the five observers (p = 0.678, 0.735, < 0.01, 0.038, and < 0.868 for observers 1, 2, 3, 4, and 5, respectively). The sensitivity of FBP-driven ULDCT was significantly lower than that of ASIR-driven ULDCT in three out of the five observers (p < 0.01 for three observers, and p = 0.064 and 0.146 for two observers). In jackknife alternative free-response receiver operating characteristic analysis, the mean values of figure-of-merit (FOM) for FBP, ASIR-driven ULDCT, and SCT were 0.682, 0.772, and 0.821, respectively, and there were no significant differences in FOM values between ASIR-driven ULDCT and SCT (p = 0.11), but the FOM value of FBP-driven ULDCT was significantly lower than that of ASIR-driven ULDCT and SCT (p = 0.01 and 0.00). Adaptive statistical iterative reconstruction-driven ULDCT delivering a radiation dose of only 0.17 mSv offers acceptable sensitivity in nodule detection compared with SCT and has better performance than FBP-driven ULDCT

Adaptive statistical iterative reconstruction-applied ultra-low-dose CT with radiography- comparable radiation dose: Usefulness for lung nodule detection

Energy Technology Data Exchange (ETDEWEB)

Yoon, Hyun Jung; Chung, Myung Jin; Hwang, Hye Sun; Lee, Kyung Soo [Dept. of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Moon, Jung Won [Dept. of Radiology, Kangbuk Samsung Hospital, Seoul (Korea, Republic of)

2015-10-15

To assess the performance of adaptive statistical iterative reconstruction (ASIR)-applied ultra-low-dose CT (ULDCT) in detecting small lung nodules. Thirty patients underwent both ULDCT and standard dose CT (SCT). After determining the reference standard nodules, five observers, blinded to the reference standard reading results, independently evaluated SCT and both subsets of ASIR- and filtered back projection (FBP)-driven ULDCT images. Data assessed by observers were compared statistically. Converted effective doses in SCT and ULDCT were 2.81 ± 0.92 and 0.17 ± 0.02 mSv, respectively. A total of 114 lung nodules were detected on SCT as a standard reference. There was no statistically significant difference in sensitivity between ASIR-driven ULDCT and SCT for three out of the five observers (p = 0.678, 0.735, < 0.01, 0.038, and < 0.868 for observers 1, 2, 3, 4, and 5, respectively). The sensitivity of FBP-driven ULDCT was significantly lower than that of ASIR-driven ULDCT in three out of the five observers (p < 0.01 for three observers, and p = 0.064 and 0.146 for two observers). In jackknife alternative free-response receiver operating characteristic analysis, the mean values of figure-of-merit (FOM) for FBP, ASIR-driven ULDCT, and SCT were 0.682, 0.772, and 0.821, respectively, and there were no significant differences in FOM values between ASIR-driven ULDCT and SCT (p = 0.11), but the FOM value of FBP-driven ULDCT was significantly lower than that of ASIR-driven ULDCT and SCT (p = 0.01 and 0.00). Adaptive statistical iterative reconstruction-driven ULDCT delivering a radiation dose of only 0.17 mSv offers acceptable sensitivity in nodule detection compared with SCT and has better performance than FBP-driven ULDCT.

Why Wait? The Influence of Academic Self-Regulation, Intrinsic Motivation, and Statistics Anxiety on Procrastination in Online Statistics

Science.gov (United States)

Dunn, Karee

2014-01-01

Online graduate education programs are expanding rapidly. Many of these programs require a statistics course, resulting in an increasing need for online statistics courses. The study reported here grew from experiences teaching online, graduate statistics courses. In seeking answers on how to improve this class, I discovered that research has yet…

Use of statistical procedures in Brazilian and international dental journals.

Science.gov (United States)

Ambrosano, Gláucia Maria Bovi; Reis, André Figueiredo; Giannini, Marcelo; Pereira, Antônio Carlos

2004-01-01

A descriptive survey was performed in order to assess the statistical content and quality of Brazilian and international dental journals, and compare their evolution throughout the last decades. The authors identified the reporting and accuracy of statistical techniques in 1000 papers published from 1970 to 2000 in seven dental journals: three Brazilian (Brazilian Dental Journal, Revista de Odontologia da Universidade de Sao Paulo and Revista de Odontologia da UNESP) and four international journals (Journal of the American Dental Association, Journal of Dental Research, Caries Research and Journal of Periodontology). Papers were divided into two time periods: from 1970 to 1989, and from 1990 to 2000. A slight increase in the number of articles that presented some form of statistical technique was noticed for Brazilian journals (from 61.0 to 66.7%), whereas for international journals, a significant increase was observed (65.8 to 92.6%). In addition, a decrease in the number of statistical errors was verified. The most commonly used statistical tests as well as the most frequent errors found in dental journals were assessed. Hopefully, this investigation will encourage dental educators to better plan the teaching of biostatistics, and to improve the statistical quality of submitted manuscripts.

Comparing Simulated and Theoretical Sampling Distributions of the U3 Person-Fit Statistic.

Science.gov (United States)

Emons, Wilco H. M.; Meijer, Rob R.; Sijtsma, Klaas

2002-01-01

Studied whether the theoretical sampling distribution of the U3 person-fit statistic is in agreement with the simulated sampling distribution under different item response theory models and varying item and test characteristics. Simulation results suggest that the use of standard normal deviates for the standardized version of the U3 statistic may…

Permutation statistical methods an integrated approach

CERN Document Server

Berry, Kenneth J; Johnston, Janis E

2016-01-01

This research monograph provides a synthesis of a number of statistical tests and measures, which, at first consideration, appear disjoint and unrelated. Numerous comparisons of permutation and classical statistical methods are presented, and the two methods are compared via probability values and, where appropriate, measures of effect size. Permutation statistical methods, compared to classical statistical methods, do not rely on theoretical distributions, avoid the usual assumptions of normality and homogeneity of variance, and depend only on the data at hand. This text takes a unique approach to explaining statistics by integrating a large variety of statistical methods, and establishing the rigor of a topic that to many may seem to be a nascent field in statistics. This topic is new in that it took modern computing power to make permutation methods available to people working in the mainstream of research. This research monograph addresses a statistically-informed audience, and can also easily serve as a ...

Order-specific fertility estimates based on perinatal statistics and statistics on out-of-hospital births

OpenAIRE

Kreyenfeld, Michaela; Peters, Frederik; Scholz, Rembrandt; Wlosnewski, Ines

2014-01-01

Until 2008, German vital statistics has not provided information on biological birth order. We have tried to close part of this gap by providing order-specific fertility rates generated from Perinatal Statistics and statistics on out-of-hospital births for the period 2001-2008. This investigation has been published in Comparative Population Studies (CPoS) (see Kreyenfeld, Scholz, Peters and Wlosnewski 2010). The CPoS-paper describes how data from the Perinatal Statistics and statistics on out...

Multiparametric statistics

CERN Document Server

Serdobolskii, Vadim Ivanovich

2007-01-01

This monograph presents mathematical theory of statistical models described by the essentially large number of unknown parameters, comparable with sample size but can also be much larger. In this meaning, the proposed theory can be called "essentially multiparametric". It is developed on the basis of the Kolmogorov asymptotic approach in which sample size increases along with the number of unknown parameters.This theory opens a way for solution of central problems of multivariate statistics, which up until now have not been solved. Traditional statistical methods based on the idea of an infinite sampling often break down in the solution of real problems, and, dependent on data, can be inefficient, unstable and even not applicable. In this situation, practical statisticians are forced to use various heuristic methods in the hope the will find a satisfactory solution.Mathematical theory developed in this book presents a regular technique for implementing new, more efficient versions of statistical procedures. ...

Implementation of International Standards in Russia's Foreign Trade Statistics

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Natalia E. Grigoruk

2015-01-01

Full Text Available The article analyzes the basic documents of international organizations in recent years, which have become the global standard for the development and improvement of statistics of foreign economic relations of most countries, including the Russian Federation. The article describes the key features of the theory and practice of modern foreign trade statistics in Russia and abroad, with an emphasis on the methodological problems of its main parts - the external trade statistics. It shows their interpretation in the most recent recommendations by UN statistical apparatus and other international organizations; considers a range of problems associated with the implementation of the national statistical practices of countries, including Russia and the countries of the Customs Union, the main international standard of foreign trade statistics - UN document "International Merchandise Trade Statistics". The main attention is paid to methodological issues such as: the criteria for selecting the objects of statistical accounting in accordance with international standards, quantitative and cost parameters of foreign trade statistics, statistical methods and estimates of commodity exports and imports, the problems of comparability of data; to a comparison of international standards in 2010 with documents on key precursor methodology of foreign trade statistics, characterized by the practice of introducing these standards in the foreign trade statistics of Russia and the countries of the Customs Union. The article analyzes the content given in the official statistical manuals of Russia foreign trade and foreign countries, covers the main methodological problems of World Trade in conjunction with the major current international statistical standards - System of National Accounts, Manual on Statistics of International Trade in Services and other documents; provides specific data describing the current structure of Russian foreign trade and especially its

Statistics and risk philosophy in human activities

International Nuclear Information System (INIS)

Failla, L.

1983-01-01

Two leading interpretations of the use of statistics exist, the first one considering statistics as a physical law regulating the phenomena studied, and the other considering statistics as a method allowing to achieve exhaustive knowledge of the phenomena. The Author chooses the second theory, applies this concept of statistics to the risk involved in human activities and discusses the different kinds of risk in this field. The Author distinguishes between the risk that can be eliminated or at least reduced, and the risk inherent in the activity itself, that can never be completely eliminated -unless the activity is suppressed-; yet, also this kind of risk can be kept under control. Furthermore, she distinguishes between risks that can or cannot be foreseen. The Author supports the theory according to which the risk foreseen must be prevented through up-to-date techniques: this should be done coherently with the aim of the activity but independently of the economic cost. The theory considering risk probability as a physical law is mainly based on events happened in the past: it uses the occurrence probability as a law. This theory accepts the statistical risk and estimates its costs, including the ''human cost''. The Author examines the different statistical possibilities to study this specific phenomenon: so, the possibility to avoid the risks may arise along with -last but not least- the opportunity to eliminate or reduce the damage connected. On the contrary, statistics used as a physical law implies the acceptable of a given amount of risk compared with the cost of improving the technical conditions required to eliminate damages. In the end, a practical example of this theory is described

A Statistical Programme Assignment Model

DEFF Research Database (Denmark)

Rosholm, Michael; Staghøj, Jonas; Svarer, Michael

When treatment effects of active labour market programmes are heterogeneous in an observable way  across the population, the allocation of the unemployed into different programmes becomes a particularly  important issue. In this paper, we present a statistical model designed to improve the present...... duration of unemployment spells may result if a statistical programme assignment model is introduced. We discuss several issues regarding the  plementation of such a system, especially the interplay between the statistical model and  case workers....

Statistical Group Comparison

CERN Document Server

Liao, Tim Futing

2011-01-01

An incomparably useful examination of statistical methods for comparisonThe nature of doing science, be it natural or social, inevitably calls for comparison. Statistical methods are at the heart of such comparison, for they not only help us gain understanding of the world around us but often define how our research is to be carried out. The need to compare between groups is best exemplified by experiments, which have clearly defined statistical methods. However, true experiments are not always possible. What complicates the matter more is a great deal of diversity in factors that are not inde

The statistical process control methods - SPC

Directory of Open Access Journals (Sweden)

Floreková Ľubica

1998-03-01

Full Text Available Methods of statistical evaluation of quality – SPC (item 20 of the documentation system of quality control of ISO norm, series 900 of various processes, products and services belong amongst basic qualitative methods that enable us to analyse and compare data pertaining to various quantitative parameters. Also they enable, based on the latter, to propose suitable interventions with the aim of improving these processes, products and services. Theoretical basis and applicatibily of the principles of the: - diagnostics of a cause and effects, - Paret analysis and Lorentz curve, - number distribution and frequency curves of random variable distribution, - Shewhart regulation charts, are presented in the contribution.

Correlation of RNA secondary structure statistics with thermodynamic stability and applications to folding.

Science.gov (United States)

Wu, Johnny C; Gardner, David P; Ozer, Stuart; Gutell, Robin R; Ren, Pengyu

2009-08-28

The accurate prediction of the secondary and tertiary structure of an RNA with different folding algorithms is dependent on several factors, including the energy functions. However, an RNA higher-order structure cannot be predicted accurately from its sequence based on a limited set of energy parameters. The inter- and intramolecular forces between this RNA and other small molecules and macromolecules, in addition to other factors in the cell such as pH, ionic strength, and temperature, influence the complex dynamics associated with transition of a single stranded RNA to its secondary and tertiary structure. Since all of the factors that affect the formation of an RNAs 3D structure cannot be determined experimentally, statistically derived potential energy has been used in the prediction of protein structure. In the current work, we evaluate the statistical free energy of various secondary structure motifs, including base-pair stacks, hairpin loops, and internal loops, using their statistical frequency obtained from the comparative analysis of more than 50,000 RNA sequences stored in the RNA Comparative Analysis Database (rCAD) at the Comparative RNA Web (CRW) Site. Statistical energy was computed from the structural statistics for several datasets. While the statistical energy for a base-pair stack correlates with experimentally derived free energy values, suggesting a Boltzmann-like distribution, variation is observed between different molecules and their location on the phylogenetic tree of life. Our statistical energy values calculated for several structural elements were utilized in the Mfold RNA-folding algorithm. The combined statistical energy values for base-pair stacks, hairpins and internal loop flanks result in a significant improvement in the accuracy of secondary structure prediction; the hairpin flanks contribute the most.

CORSSA: The Community Online Resource for Statistical Seismicity Analysis

Science.gov (United States)

Michael, Andrew J.; Wiemer, Stefan

2010-01-01

Statistical seismology is the application of rigorous statistical methods to earthquake science with the goal of improving our knowledge of how the earth works. Within statistical seismology there is a strong emphasis on the analysis of seismicity data in order to improve our scientific understanding of earthquakes and to improve the evaluation and testing of earthquake forecasts, earthquake early warning, and seismic hazards assessments. Given the societal importance of these applications, statistical seismology must be done well. Unfortunately, a lack of educational resources and available software tools make it difficult for students and new practitioners to learn about this discipline. The goal of the Community Online Resource for Statistical Seismicity Analysis (CORSSA) is to promote excellence in statistical seismology by providing the knowledge and resources necessary to understand and implement the best practices, so that the reader can apply these methods to their own research. This introduction describes the motivation for and vision of CORRSA. It also describes its structure and contents.

Strategies of statistical windows in PET image reconstruction to improve the user’s real time experience

Science.gov (United States)

Moliner, L.; Correcher, C.; Gimenez-Alventosa, V.; Ilisie, V.; Alvarez, J.; Sanchez, S.; Rodríguez-Alvarez, M. J.

2017-11-01

Nowadays, with the increase of the computational power of modern computers together with the state-of-the-art reconstruction algorithms, it is possible to obtain Positron Emission Tomography (PET) images in practically real time. These facts open the door to new applications such as radio-pharmaceuticals tracking inside the body or the use of PET for image-guided procedures, such as biopsy interventions, among others. This work is a proof of concept that aims to improve the user experience with real time PET images. Fixed, incremental, overlapping, sliding and hybrid windows are the different statistical combinations of data blocks used to generate intermediate images in order to follow the path of the activity in the Field Of View (FOV). To evaluate these different combinations, a point source is placed in a dedicated breast PET device and moved along the FOV. These acquisitions are reconstructed according to the different statistical windows, resulting in a smoother transition of positions for the image reconstructions that use the sliding and hybrid window.

Statistics of Parameter Estimates: A Concrete Example

KAUST Repository

Aguilar, Oscar

2015-01-01

© 2015 Society for Industrial and Applied Mathematics. Most mathematical models include parameters that need to be determined from measurements. The estimated values of these parameters and their uncertainties depend on assumptions made about noise levels, models, or prior knowledge. But what can we say about the validity of such estimates, and the influence of these assumptions? This paper is concerned with methods to address these questions, and for didactic purposes it is written in the context of a concrete nonlinear parameter estimation problem. We will use the results of a physical experiment conducted by Allmaras et al. at Texas A&M University [M. Allmaras et al., SIAM Rev., 55 (2013), pp. 149-167] to illustrate the importance of validation procedures for statistical parameter estimation. We describe statistical methods and data analysis tools to check the choices of likelihood and prior distributions, and provide examples of how to compare Bayesian results with those obtained by non-Bayesian methods based on different types of assumptions. We explain how different statistical methods can be used in complementary ways to improve the understanding of parameter estimates and their uncertainties.

Statistical methods for detecting and comparing periodic data and their application to the nycthemeral rhythm of bodily harm: A population based study

LENUS (Irish Health Repository)

Stroebel, Armin M

2010-11-08

Abstract Background Animals, including humans, exhibit a variety of biological rhythms. This article describes a method for the detection and simultaneous comparison of multiple nycthemeral rhythms. Methods A statistical method for detecting periodic patterns in time-related data via harmonic regression is described. The method is particularly capable of detecting nycthemeral rhythms in medical data. Additionally a method for simultaneously comparing two or more periodic patterns is described, which derives from the analysis of variance (ANOVA). This method statistically confirms or rejects equality of periodic patterns. Mathematical descriptions of the detecting method and the comparing method are displayed. Results Nycthemeral rhythms of incidents of bodily harm in Middle Franconia are analyzed in order to demonstrate both methods. Every day of the week showed a significant nycthemeral rhythm of bodily harm. These seven patterns of the week were compared to each other revealing only two different nycthemeral rhythms, one for Friday and Saturday and one for the other weekdays.

On Improving the Quality and Interpretation of Environmental Assessments using Statistical Analysis and Geographic Information Systems

Science.gov (United States)

Karuppiah, R.; Faldi, A.; Laurenzi, I.; Usadi, A.; Venkatesh, A.

2014-12-01

An increasing number of studies are focused on assessing the environmental footprint of different products and processes, especially using life cycle assessment (LCA). This work shows how combining statistical methods and Geographic Information Systems (GIS) with environmental analyses can help improve the quality of results and their interpretation. Most environmental assessments in literature yield single numbers that characterize the environmental impact of a process/product - typically global or country averages, often unchanging in time. In this work, we show how statistical analysis and GIS can help address these limitations. For example, we demonstrate a method to separately quantify uncertainty and variability in the result of LCA models using a power generation case study. This is important for rigorous comparisons between the impacts of different processes. Another challenge is lack of data that can affect the rigor of LCAs. We have developed an approach to estimate environmental impacts of incompletely characterized processes using predictive statistical models. This method is applied to estimate unreported coal power plant emissions in several world regions. There is also a general lack of spatio-temporal characterization of the results in environmental analyses. For instance, studies that focus on water usage do not put in context where and when water is withdrawn. Through the use of hydrological modeling combined with GIS, we quantify water stress on a regional and seasonal basis to understand water supply and demand risks for multiple users. Another example where it is important to consider regional dependency of impacts is when characterizing how agricultural land occupation affects biodiversity in a region. We developed a data-driven methodology used in conjuction with GIS to determine if there is a statistically significant difference between the impacts of growing different crops on different species in various biomes of the world.

Improved radiograph measurement inter-observer reliability by use of statistical shape models

Energy Technology Data Exchange (ETDEWEB)

Pegg, E.C., E-mail: elise.pegg@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Mellon, S.J., E-mail: stephen.mellon@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Salmon, G. [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Alvand, A., E-mail: abtin.alvand@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Pandit, H., E-mail: hemant.pandit@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Murray, D.W., E-mail: david.murray@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom); Gill, H.S., E-mail: richie.gill@ndorms.ox.ac.uk [University of Oxford, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD (United Kingdom)

2012-10-15

Pre- and post-operative radiographs of patients undergoing joint arthroplasty are often examined for a variety of purposes including preoperative planning and patient assessment. This work examines the feasibility of using active shape models (ASM) to semi-automate measurements from post-operative radiographs for the specific case of the Oxford™ Unicompartmental Knee. Measurements of the proximal tibia and the position of the tibial tray were made using the ASM model and manually. Data were obtained by four observers and one observer took four sets of measurements to allow assessment of the inter- and intra-observer reliability, respectively. The parameters measured were the tibial tray angle, the tray overhang, the tray size, the sagittal cut position, the resection level and the tibial width. Results demonstrated improved reliability (average of 27% and 11.2% increase for intra- and inter-reliability, respectively) and equivalent accuracy (p > 0.05 for compared data values) for all of the measurements using the ASM model, with the exception of the tray overhang (p = 0.0001). Less time (15 s) was required to take measurements using the ASM model compared with manual measurements, which was significant. These encouraging results indicate that semi-automated measurement techniques could improve the reliability of radiographic measurements.

Improved radiograph measurement inter-observer reliability by use of statistical shape models

International Nuclear Information System (INIS)

Pegg, E.C.; Mellon, S.J.; Salmon, G.; Alvand, A.; Pandit, H.; Murray, D.W.; Gill, H.S.

2012-01-01

Pre- and post-operative radiographs of patients undergoing joint arthroplasty are often examined for a variety of purposes including preoperative planning and patient assessment. This work examines the feasibility of using active shape models (ASM) to semi-automate measurements from post-operative radiographs for the specific case of the Oxford™ Unicompartmental Knee. Measurements of the proximal tibia and the position of the tibial tray were made using the ASM model and manually. Data were obtained by four observers and one observer took four sets of measurements to allow assessment of the inter- and intra-observer reliability, respectively. The parameters measured were the tibial tray angle, the tray overhang, the tray size, the sagittal cut position, the resection level and the tibial width. Results demonstrated improved reliability (average of 27% and 11.2% increase for intra- and inter-reliability, respectively) and equivalent accuracy (p > 0.05 for compared data values) for all of the measurements using the ASM model, with the exception of the tray overhang (p = 0.0001). Less time (15 s) was required to take measurements using the ASM model compared with manual measurements, which was significant. These encouraging results indicate that semi-automated measurement techniques could improve the reliability of radiographic measurements

Comparing the Goodness of Different Statistical Criteria for Evaluating the Soil Water Infiltration Models

Directory of Open Access Journals (Sweden)

S. Mirzaee

2016-02-01

Full Text Available Introduction: The infiltration process is one of the most important components of the hydrologic cycle. Quantifying the infiltration water into soil is of great importance in watershed management. Prediction of flooding, erosion and pollutant transport all depends on the rate of runoff which is directly affected by the rate of infiltration. Quantification of infiltration water into soil is also necessary to determine the availability of water for crop growth and to estimate the amount of additional water needed for irrigation. Thus, an accurate model is required to estimate infiltration of water into soil. The ability of physical and empirical models in simulation of soil processes is commonly measured through comparisons of simulated and observed values. For these reasons, a large variety of indices have been proposed and used over the years in comparison of infiltration water into soil models. Among the proposed indices, some are absolute criteria such as the widely used root mean square error (RMSE, while others are relative criteria (i.e. normalized such as the Nash and Sutcliffe (1970 efficiency criterion (NSE. Selecting and using appropriate statistical criteria to evaluate and interpretation of the results for infiltration water into soil models is essential because each of the used criteria focus on specific types of errors. Also, descriptions of various goodness of fit indices or indicators including their advantages and shortcomings, and rigorous discussions on the suitability of each index are very important. The objective of this study is to compare the goodness of different statistical criteria to evaluate infiltration of water into soil models. Comparison techniques were considered to define the best models: coefficient of determination (R2, root mean square error (RMSE, efficiency criteria (NSEI and modified forms (such as NSEjI, NSESQRTI, NSElnI and NSEiI. Comparatively little work has been carried out on the meaning and

"Dear Fresher …"--How Online Questionnaires Can Improve Learning and Teaching Statistics

Science.gov (United States)

Bebermeier, Sarah; Nussbeck, Fridtjof W.; Ontrup, Greta

2015-01-01

Lecturers teaching statistics are faced with several challenges supporting students' learning in appropriate ways. A variety of methods and tools exist to facilitate students' learning on statistics courses. The online questionnaires presented in this report are a new, slightly different computer-based tool: the central aim was to support students…

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

Directory of Open Access Journals (Sweden)

J. Sunil Rao

2007-01-01

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

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

Science.gov (United States)

Samuelson, Frank; Abbey, Craig

2016-11-01

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

Difference in Learning among Students Doing Pen-and-Paper Homework Compared to Web-Based Homework in an Introductory Statistics Course

Science.gov (United States)

Jonsdottir, Anna Helga; Bjornsdottir, Audbjorg; Stefansson, Gunnar

2017-01-01

A repeated crossover experiment comparing learning among students handing in pen-and-paper homework (PPH) with students handing in web-based homework (WBH) has been conducted. The system used in the experiments, the tutor-web, has been used to deliver homework problems to thousands of students in mathematics and statistics over several years.…

Lidar measurements of plume statistics

DEFF Research Database (Denmark)

Ejsing Jørgensen, Hans; Mikkelsen, T.

1993-01-01

of measured crosswind concentration profiles, the following statistics were obtained: 1) Mean profile, 2) Root mean square profile, 3) Fluctuation intensities,and 4)Intermittency factors. Furthermore, some experimentally determined probability density functions (pdf's) of the fluctuations are presented. All...... the measured statistics are referred to a fixed and a 'moving' frame of reference, the latter being defined as a frame of reference from which the (low frequency) plume meander is removed. Finally, the measured statistics are compared with statistics on concentration fluctuations obtained with a simple puff...

Environmental radiations and childhood dynamic statistics

International Nuclear Information System (INIS)

Sakka, Masatoshi

1981-01-01

In Fukushima prefecture the first nuclear power plant attained criticality in 1971. Since then 6 reactors have been in operation. Increasing concern is the possible adverse effects due to ionizing radiations released from nuclear reactors. As the radiation level around the nuclear power plants is usually low, induced effects are necessarily delayed ones which require tens of years to appear. Among other tissues, embryos and foetuses are most radiosensitive and induced effects result in the change of childhood dynamic statistics. In this report dynamic statistics including stillbirth, perinatal death, neonatal death, infant death, 3rd year examinations were surveyed in 18 health centers in the prefecture from 1961 to 1979. Environmental radiation levels in each district (health centers) were compared and were arranged in order, 1, 2, ... etc. Dynamic statistics were also compared for each district and were arranged in order. Order correlation coefficients were calculated and a linearity between radiation level and health status was tested. No significant values were obtained ranging from 0.66 to -0.43 of correlation coefficients. Still birth decreased 4.4%/y since 1963 and neonatal death decreased 6.7%/y and infant death also decreased 8.7%/y since 1957 on an average. These decreases were negatively correlated with the proliferation of water supply service, sewage service and increase of physicians in 18 districts including 2 which are under continuous observation of environmental radiations released from nuclear power plants. Childhood dynamic statistics have been turning better in the last 10 years in prefecture with the difference of 47 mR/y (lowest values of 56 mR/y on an average in 3 prefectures and highest of 103 mR/y in 4 ones). Environmental radiation may initiate adverse effects on prenatal lives but the hygienic improvement in recent years must extinguish the promotion of the adverse effects. This may be a plausible explanation. (author)

Exposure time independent summary statistics for assessment of drug dependent cell line growth inhibition.

Science.gov (United States)

Falgreen, Steffen; Laursen, Maria Bach; Bødker, Julie Støve; Kjeldsen, Malene Krag; Schmitz, Alexander; Nyegaard, Mette; Johnsen, Hans Erik; Dybkær, Karen; Bøgsted, Martin

2014-06-05

In vitro generated dose-response curves of human cancer cell lines are widely used to develop new therapeutics. The curves are summarised by simplified statistics that ignore the conventionally used dose-response curves' dependency on drug exposure time and growth kinetics. This may lead to suboptimal exploitation of data and biased conclusions on the potential of the drug in question. Therefore we set out to improve the dose-response assessments by eliminating the impact of time dependency. First, a mathematical model for drug induced cell growth inhibition was formulated and used to derive novel dose-response curves and improved summary statistics that are independent of time under the proposed model. Next, a statistical analysis workflow for estimating the improved statistics was suggested consisting of 1) nonlinear regression models for estimation of cell counts and doubling times, 2) isotonic regression for modelling the suggested dose-response curves, and 3) resampling based method for assessing variation of the novel summary statistics. We document that conventionally used summary statistics for dose-response experiments depend on time so that fast growing cell lines compared to slowly growing ones are considered overly sensitive. The adequacy of the mathematical model is tested for doxorubicin and found to fit real data to an acceptable degree. Dose-response data from the NCI60 drug screen were used to illustrate the time dependency and demonstrate an adjustment correcting for it. The applicability of the workflow was illustrated by simulation and application on a doxorubicin growth inhibition screen. The simulations show that under the proposed mathematical model the suggested statistical workflow results in unbiased estimates of the time independent summary statistics. Variance estimates of the novel summary statistics are used to conclude that the doxorubicin screen covers a significant diverse range of responses ensuring it is useful for biological

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

Science.gov (United States)

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

2018-01-01

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

Image statistics and nonlinear artifacts in composed transmission x-ray tomography

International Nuclear Information System (INIS)

Duerinckx, A.J.G.

1979-01-01

Knowledge of the image quality and image statistics in Computed Tomography (CT) images obtained with transmission x-ray CT scanners can increase the amount of clinically useful information that can be retrieved. Artifacts caused by nonlinear shadows are strongly object-dependent and are visible over larger areas of the image. No simple technique exists for their complete elimination. One source of artifacts in the first order statistics is the nonlinearities in the measured shadow or projection data used to reconstruct the image. One of the leading causes is the polychromaticity of the x-ray beam used in transmission CT scanners. Ways to improve the resulting image quality and techniques to extract additional information using dual energy scanning are discussed. A unique formalism consisting of a vector representation of the material dependence of the photon-tissue interactions is generalized to allow an in depth analysis. Poly-correction algorithms are compared using this analytic approach. Both quantum and detector electronic noise decrease the quality or information content of first order statistics. Preliminary results are presented using an heuristic adaptive nonlinear noise filter system for projection data. This filter system can be improved and/or modified to remove artifacts in both first and second order image statistics. Artifacts in the second order image statistics arise from the contribution of quantum noise. This can be described with a nonlinear detection equivalent model, similar to the model used to study artifacts in first order statistics. When analyzing these artifacts in second order statistics, one can divide them into linear artifacts, which do not present any problem of interpretation, and nonlinear artifacts, referred to as noise artifacts. A study of noise artifacts is presented together with a discussion of their relative importance in diagnostic radiology

Statistical methods for nuclear material management

International Nuclear Information System (INIS)

Bowen, W.M.; Bennett, C.A.

1988-12-01

This book is intended as a reference manual of statistical methodology for nuclear material management practitioners. It describes statistical methods currently or potentially important in nuclear material management, explains the choice of methods for specific applications, and provides examples of practical applications to nuclear material management problems. Together with the accompanying training manual, which contains fully worked out problems keyed to each chapter, this book can also be used as a textbook for courses in statistical methods for nuclear material management. It should provide increased understanding and guidance to help improve the application of statistical methods to nuclear material management problems

Statistical methods for nuclear material management

Energy Technology Data Exchange (ETDEWEB)

Bowen W.M.; Bennett, C.A. (eds.)

1988-12-01

This book is intended as a reference manual of statistical methodology for nuclear material management practitioners. It describes statistical methods currently or potentially important in nuclear material management, explains the choice of methods for specific applications, and provides examples of practical applications to nuclear material management problems. Together with the accompanying training manual, which contains fully worked out problems keyed to each chapter, this book can also be used as a textbook for courses in statistical methods for nuclear material management. It should provide increased understanding and guidance to help improve the application of statistical methods to nuclear material management problems.

Effect of Internet-Based Cognitive Apprenticeship Model (i-CAM) on Statistics Learning among Postgraduate Students.

Science.gov (United States)

Saadati, Farzaneh; Ahmad Tarmizi, Rohani; Mohd Ayub, Ahmad Fauzi; Abu Bakar, Kamariah

2015-01-01

Because students' ability to use statistics, which is mathematical in nature, is one of the concerns of educators, embedding within an e-learning system the pedagogical characteristics of learning is 'value added' because it facilitates the conventional method of learning mathematics. Many researchers emphasize the effectiveness of cognitive apprenticeship in learning and problem solving in the workplace. In a cognitive apprenticeship learning model, skills are learned within a community of practitioners through observation of modelling and then practice plus coaching. This study utilized an internet-based Cognitive Apprenticeship Model (i-CAM) in three phases and evaluated its effectiveness for improving statistics problem-solving performance among postgraduate students. The results showed that, when compared to the conventional mathematics learning model, the i-CAM could significantly promote students' problem-solving performance at the end of each phase. In addition, the combination of the differences in students' test scores were considered to be statistically significant after controlling for the pre-test scores. The findings conveyed in this paper confirmed the considerable value of i-CAM in the improvement of statistics learning for non-specialized postgraduate students.

Improving cerebellar segmentation with statistical fusion

Science.gov (United States)

Plassard, Andrew J.; Yang, Zhen; Prince, Jerry L.; Claassen, Daniel O.; Landman, Bennett A.

2016-03-01

The cerebellum is a somatotopically organized central component of the central nervous system well known to be involved with motor coordination and increasingly recognized roles in cognition and planning. Recent work in multiatlas labeling has created methods that offer the potential for fully automated 3-D parcellation of the cerebellar lobules and vermis (which are organizationally equivalent to cortical gray matter areas). This work explores the trade offs of using different statistical fusion techniques and post hoc optimizations in two datasets with distinct imaging protocols. We offer a novel fusion technique by extending the ideas of the Selective and Iterative Method for Performance Level Estimation (SIMPLE) to a patch-based performance model. We demonstrate the effectiveness of our algorithm, Non- Local SIMPLE, for segmentation of a mixed population of healthy subjects and patients with severe cerebellar anatomy. Under the first imaging protocol, we show that Non-Local SIMPLE outperforms previous gold-standard segmentation techniques. In the second imaging protocol, we show that Non-Local SIMPLE outperforms previous gold standard techniques but is outperformed by a non-locally weighted vote with the deeper population of atlases available. This work advances the state of the art in open source cerebellar segmentation algorithms and offers the opportunity for routinely including cerebellar segmentation in magnetic resonance imaging studies that acquire whole brain T1-weighted volumes with approximately 1 mm isotropic resolution.

Machines that go "ping" may improve balance but may not improve mobility or reduce risk of falls: a systematic review.

Science.gov (United States)

Dennett, Amy M; Taylor, Nicholas F

2015-01-01

To determine the effectiveness of computer-based electronic devices that provide feedback in improving mobility and balance and reducing falls. Randomized controlled trials were searched from the earliest available date to August 2013. Standardized mean differences were used to complete meta-analyses, with statistical heterogeneity being described with the I-squared statistic. The GRADE approach was used to summarize the level of evidence for each completed meta-analysis. Risk of bias for individual trials was assessed with the (Physiotherapy Evidence Database) PEDro scale. Thirty trials were included. There was high-quality evidence that computerized devices can improve dynamic balance in people with a neurological condition compared with no therapy. There was low-to-moderate-quality evidence that computerized devices have no significant effect on mobility, falls efficacy and falls risk in community-dwelling older adults, and people with a neurological condition compared with physiotherapy. There is high-quality evidence that computerized devices that provide feedback may be useful in improving balance in people with neurological conditions compared with no therapy, but there is a lack of evidence supporting more meaningful changes in mobility and falls risk.

The value of model averaging and dynamical climate model predictions for improving statistical seasonal streamflow forecasts over Australia

Science.gov (United States)

Pokhrel, Prafulla; Wang, Q. J.; Robertson, David E.

2013-10-01

Seasonal streamflow forecasts are valuable for planning and allocation of water resources. In Australia, the Bureau of Meteorology employs a statistical method to forecast seasonal streamflows. The method uses predictors that are related to catchment wetness at the start of a forecast period and to climate during the forecast period. For the latter, a predictor is selected among a number of lagged climate indices as candidates to give the "best" model in terms of model performance in cross validation. This study investigates two strategies for further improvement in seasonal streamflow forecasts. The first is to combine, through Bayesian model averaging, multiple candidate models with different lagged climate indices as predictors, to take advantage of different predictive strengths of the multiple models. The second strategy is to introduce additional candidate models, using rainfall and sea surface temperature predictions from a global climate model as predictors. This is to take advantage of the direct simulations of various dynamic processes. The results show that combining forecasts from multiple statistical models generally yields more skillful forecasts than using only the best model and appears to moderate the worst forecast errors. The use of rainfall predictions from the dynamical climate model marginally improves the streamflow forecasts when viewed over all the study catchments and seasons, but the use of sea surface temperature predictions provide little additional benefit.

A heuristic statistical stopping rule for iterative reconstruction in emission tomography

International Nuclear Information System (INIS)

Ben Bouallegue, F.; Mariano-Goulart, D.; Crouzet, J.F.

2013-01-01

We propose a statistical stopping criterion for iterative reconstruction in emission tomography based on a heuristic statistical description of the reconstruction process. The method was assessed for maximum likelihood expectation maximization (MLEM) reconstruction. Based on Monte-Carlo numerical simulations and using a perfectly modeled system matrix, our method was compared with classical iterative reconstruction followed by low-pass filtering in terms of Euclidian distance to the exact object, noise, and resolution. The stopping criterion was then evaluated with realistic PET data of a Hoffman brain phantom produced using the Geant4 application in emission tomography (GATE) platform for different count levels. The numerical experiments showed that compared with the classical method, our technique yielded significant improvement of the noise-resolution tradeoff for a wide range of counting statistics compatible with routine clinical settings. When working with realistic data, the stopping rule allowed a qualitatively and quantitatively efficient determination of the optimal image. Our method appears to give a reliable estimation of the optimal stopping point for iterative reconstruction. It should thus be of practical interest as it produces images with similar or better quality than classical post-filtered iterative reconstruction with a mastered computation time. (author)

Methodological differences behind energy statistics for steel production – Implications when monitoring energy efficiency

International Nuclear Information System (INIS)

Morfeldt, Johannes; Silveira, Semida

2014-01-01

Energy efficiency indicators used for evaluating industrial activities at the national level are often based on statistics reported in international databases. In the case of the Swedish iron and steel sector, energy consumption statistics published by Odyssee, Eurostat, the IEA (International Energy Agency), and the United Nations differ, resulting in diverging energy efficiency indicators. For certain years, the specific energy consumption for steel is twice as high if based on Odyssee statistics instead of statistics from the IEA. The analysis revealed that the assumptions behind the allocation of coal and coke used in blast furnaces as energy consumption or energy transformation are the major cause for these differences. Furthermore, the differences are also related to errors in the statistical data resulting from two different surveys that support the data. The allocation of coal and coke has implications when promoting resource as well as energy efficiency at the systems level. Eurostat's definition of energy consumption is more robust compared to the definitions proposed by other organisations. Nevertheless, additional data and improved energy efficiency indicators are needed to fully monitor the iron and steel sector's energy system and promote improvements towards a greener economy at large. - Highlights: • Energy statistics for the iron and steel sector diverge in international databases. • Varying methods have implications when monitoring energy and resource efficiency. • Allocation of blast furnaces as transformation activities is behind the differences. • Different statistical surveys and human error also contribute to diverging results

A COMPARATIVE STUDY OF TYMPANOPLASTY USING SLICED CARTILAGE GRAFT VS. TEMPORALIS FASCIA GRAFT

Directory of Open Access Journals (Sweden)

Rahul Ashok Telang

2018-02-01

Full Text Available BACKGROUND The objective of the study was to compare the hearing improvement after using sliced cartilage graft with that of temporalis fascia and to compare the graft take-up between the two graft materials. MATERIALS AND METHODS A prospective clinical study including 60 patients with chronic mucosal otitis media, who were selected randomly from the outpatient department, after obtaining their consent were divided into 2 groups of 30 each, and evaluated according the study protocol. Their pre-operative audiometry was recorded and both groups of patients underwent surgery with one of the graft materials- temporalis fascia or sliced tragal cartilage with a thickness of 0.5 mm. All patients were regularly followed up and post-operative audiometry was done at 3 months. The hearing improvement in the form of closure of air-bone-gap and graft take-up was analysed statistically. RESULTS The temporalis fascia graft group had a pre-operative ABG of 22.33 ± 6.24 dB and post-operative ABG of 12.33 ± 4.72 dB with hearing improvement of 10.00 dB. The sliced cartilage graft group had a pre-operative ABG of 20.77 ± 5.75 dB and postoperative ABG of 10.50 ± 4.46 dB with hearing improvement of 10.27 dB. In the temporalis fascia group, 28 (93.3% patients had good graft take-up and in the sliced cartilage group 29 (96.7% had good graft take-up. There was statistically significant hearing improvement in both of our study groups but there was no statistically significant difference between the two groups. There was no statistically significant difference in graft take-up also. CONCLUSION Sliced cartilage graft is a good auto-graft material in tympanoplasty, which can give good hearing improvement and has good graft take-up, which is comparable with that of temporalis fascia.

Building information for systematic improvement of the prevention of hospital-acquired pressure ulcers with statistical process control charts and regression.

Science.gov (United States)

Padula, William V; Mishra, Manish K; Weaver, Christopher D; Yilmaz, Taygan; Splaine, Mark E

2012-06-01

To demonstrate complementary results of regression and statistical process control (SPC) chart analyses for hospital-acquired pressure ulcers (HAPUs), and identify possible links between changes and opportunities for improvement between hospital microsystems and macrosystems. Ordinary least squares and panel data regression of retrospective hospital billing data, and SPC charts of prospective patient records for a US tertiary-care facility (2004-2007). A prospective cohort of hospital inpatients at risk for HAPUs was the study population. There were 337 HAPU incidences hospital wide among 43 844 inpatients. A probit regression model predicted the correlation of age, gender and length of stay on HAPU incidence (pseudo R(2)=0.096). Panel data analysis determined that for each additional day in the hospital, there was a 0.28% increase in the likelihood of HAPU incidence. A p-chart of HAPU incidence showed a mean incidence rate of 1.17% remaining in statistical control. A t-chart showed the average time between events for the last 25 HAPUs was 13.25 days. There was one 57-day period between two incidences during the observation period. A p-chart addressing Braden scale assessments showed that 40.5% of all patients were risk stratified for HAPUs upon admission. SPC charts complement standard regression analysis. SPC amplifies patient outcomes at the microsystem level and is useful for guiding quality improvement. Macrosystems should monitor effective quality improvement initiatives in microsystems and aid the spread of successful initiatives to other microsystems, followed by system-wide analysis with regression. Although HAPU incidence in this study is below the national mean, there is still room to improve HAPU incidence in this hospital setting since 0% incidence is theoretically achievable. Further assessment of pressure ulcer incidence could illustrate improvement in the quality of care and prevent HAPUs.

Journal Data Sharing Policies and Statistical Reporting Inconsistencies in Psychology

Directory of Open Access Journals (Sweden)

Michèle B. Nuijten

2017-12-01

Full Text Available In this paper, we present three retrospective observational studies that investigate the relation between data sharing and statistical reporting inconsistencies. Previous research found that reluctance to share data was related to a higher prevalence of statistical errors, often in the direction of statistical significance (Wicherts, Bakker, & Molenaar, 2011. We therefore hypothesized that journal policies about data sharing and data sharing itself would reduce these inconsistencies. In Study 1, we compared the prevalence of reporting inconsistencies in two similar journals on decision making with different data sharing policies. In Study 2, we compared reporting inconsistencies in psychology articles published in PLOS journals (with a data sharing policy and Frontiers in Psychology (without a stipulated data sharing policy. In Study 3, we looked at papers published in the journal Psychological Science to check whether papers with or without an Open Practice Badge differed in the prevalence of reporting errors. Overall, we found no relationship between data sharing and reporting inconsistencies. We did find that journal policies on data sharing seem extremely effective in promoting data sharing. We argue that open data is essential in improving the quality of psychological science, and we discuss ways to detect and reduce reporting inconsistencies in the literature.

A New Global Policy Regime Founded on Invalid Statistics? Hanushek, Woessmann, PISA, and Economic Growth

Science.gov (United States)

Komatsu, Hikaru; Rappleye, Jeremy

2017-01-01

Several recent, highly influential comparative studies have made strong statistical claims that improvements on global learning assessments such as PISA will lead to higher GDP growth rates. These claims have provided the primary source of legitimation for policy reforms championed by leading international organisations, most notably the World…

Irrigated Area Maps and Statistics of India Using Remote Sensing and National Statistics

Directory of Open Access Journals (Sweden)

Prasad S. Thenkabail

2009-04-01

Full Text Available The goal of this research was to compare the remote-sensing derived irrigated areas with census-derived statistics reported in the national system. India, which has nearly 30% of global annualized irrigated areas (AIAs, and is the leading irrigated area country in the World, along with China, was chosen for the study. Irrigated areas were derived for nominal year 2000 using time-series remote sensing at two spatial resolutions: (a 10-km Advanced Very High Resolution Radiometer (AVHRR and (b 500-m Moderate Resolution Imaging Spectroradiometer (MODIS. These areas were compared with the Indian National Statistical Data on irrigated areas reported by the: (a Directorate of Economics and Statistics (DES of the Ministry of Agriculture (MOA, and (b Ministry of Water Resources (MoWR. A state-by-state comparison of remote sensing derived irrigated areas when compared with MoWR derived irrigation potential utilized (IPU, an equivalent of AIA, provided a high degree of correlation with R2 values of: (a 0.79 with 10-km, and (b 0.85 with MODIS 500-m. However, the remote sensing derived irrigated area estimates for India were consistently higher than the irrigated areas reported by the national statistics. The remote sensing derived total area available for irrigation (TAAI, which does not consider intensity of irrigation, was 101 million hectares (Mha using 10-km and 113 Mha using 500-m. The AIAs, which considers intensity of irrigation, was 132 Mha using 10-km and 146 Mha using 500-m. In contrast the IPU, an equivalent of AIAs, as reported by MoWR was 83 Mha. There are “large variations” in irrigated area statistics reported, even between two ministries (e.g., Directorate of Statistics of Ministry of Agriculture and Ministry of Water Resources of the same national system. The causes include: (a reluctance on part of the states to furnish irrigated area data in view of their vested interests in sharing of water, and (b reporting of large volumes of data

Statistical modeling to support power system planning

Science.gov (United States)

Staid, Andrea

This dissertation focuses on data-analytic approaches that improve our understanding of power system applications to promote better decision-making. It tackles issues of risk analysis, uncertainty management, resource estimation, and the impacts of climate change. Tools of data mining and statistical modeling are used to bring new insight to a variety of complex problems facing today's power system. The overarching goal of this research is to improve the understanding of the power system risk environment for improved operation, investment, and planning decisions. The first chapter introduces some challenges faced in planning for a sustainable power system. Chapter 2 analyzes the driving factors behind the disparity in wind energy investments among states with a goal of determining the impact that state-level policies have on incentivizing wind energy. Findings show that policy differences do not explain the disparities; physical and geographical factors are more important. Chapter 3 extends conventional wind forecasting to a risk-based focus of predicting maximum wind speeds, which are dangerous for offshore operations. Statistical models are presented that issue probabilistic predictions for the highest wind speed expected in a three-hour interval. These models achieve a high degree of accuracy and their use can improve safety and reliability in practice. Chapter 4 examines the challenges of wind power estimation for onshore wind farms. Several methods for wind power resource assessment are compared, and the weaknesses of the Jensen model are demonstrated. For two onshore farms, statistical models outperform other methods, even when very little information is known about the wind farm. Lastly, chapter 5 focuses on the power system more broadly in the context of the risks expected from tropical cyclones in a changing climate. Risks to U.S. power system infrastructure are simulated under different scenarios of tropical cyclone behavior that may result from climate

An improved method for statistical analysis of raw accelerator mass spectrometry data

International Nuclear Information System (INIS)

Gutjahr, A.; Phillips, F.; Kubik, P.W.; Elmore, D.

1987-01-01

Hierarchical statistical analysis is an appropriate method for statistical treatment of raw accelerator mass spectrometry (AMS) data. Using Monte Carlo simulations we show that this method yields more accurate estimates of isotope ratios and analytical uncertainty than the generally used propagation of errors approach. The hierarchical analysis is also useful in design of experiments because it can be used to identify sources of variability. 8 refs., 2 figs

Cluster Statistics of BTW Automata

International Nuclear Information System (INIS)

Ajanta Bhowal Acharyya

2011-01-01

The cluster statistics of BTW automata in the SOC states are obtained by extensive computer simulation. Various moments of the clusters are calculated and few results are compared with earlier available numerical estimates and exact results. Reasonably good agreement is observed. An extended statistical analysis has been made. (author)

Powerful Statistical Inference for Nested Data Using Sufficient Summary Statistics

Science.gov (United States)

Dowding, Irene; Haufe, Stefan

2018-01-01

Hierarchically-organized data arise naturally in many psychology and neuroscience studies. As the standard assumption of independent and identically distributed samples does not hold for such data, two important problems are to accurately estimate group-level effect sizes, and to obtain powerful statistical tests against group-level null hypotheses. A common approach is to summarize subject-level data by a single quantity per subject, which is often the mean or the difference between class means, and treat these as samples in a group-level t-test. This “naive” approach is, however, suboptimal in terms of statistical power, as it ignores information about the intra-subject variance. To address this issue, we review several approaches to deal with nested data, with a focus on methods that are easy to implement. With what we call the sufficient-summary-statistic approach, we highlight a computationally efficient technique that can improve statistical power by taking into account within-subject variances, and we provide step-by-step instructions on how to apply this approach to a number of frequently-used measures of effect size. The properties of the reviewed approaches and the potential benefits over a group-level t-test are quantitatively assessed on simulated data and demonstrated on EEG data from a simulated-driving experiment. PMID:29615885

A comparative analysis of badminton game instructions effect of non ...

African Journals Online (AJOL)

... drop shot and smash in doubles game play, ANCOVA and ANOVA statistics indicated significant improved performance via NP compared to LP. Conclusion, implementing NP in schools would further strengthen TGfU as teachers can adjust tactics, skill tasks to the performer's abilities and situated learning environment.

Reduction of Complications of Local Anaesthesia in Dental Healthcare Setups by Application of the Six Sigma Methodology: A Statistical Quality Improvement Technique.

Science.gov (United States)

Akifuddin, Syed; Khatoon, Farheen

2015-12-01

Health care faces challenges due to complications, inefficiencies and other concerns that threaten the safety of patients. The purpose of his study was to identify causes of complications encountered after administration of local anaesthesia for dental and oral surgical procedures and to reduce the incidence of complications by introduction of six sigma methodology. DMAIC (Define, Measure, Analyse, Improve and Control) process of Six Sigma was taken into consideration to reduce the incidence of complications encountered after administration of local anaesthesia injections for dental and oral surgical procedures using failure mode and effect analysis. Pareto analysis was taken into consideration to analyse the most recurring complications. Paired z-sample test using Minitab Statistical Inference and Fisher's exact test was used to statistically analyse the obtained data. The p-value six sigma improvement methodology in healthcare tends to deliver consistently better results to the patients as well as hospitals and results in better patient compliance as well as satisfaction.

Tucker tensor analysis of Matern functions in spatial statistics

KAUST Repository

Litvinenko, Alexander

2018-04-20

Low-rank Tucker tensor methods in spatial statistics 1. Motivation: improve statistical models 2. Motivation: disadvantages of matrices 3. Tools: Tucker tensor format 4. Tensor approximation of Matern covariance function via FFT 5. Typical statistical operations in Tucker tensor format 6. Numerical experiments

Assessment and improvement of statistical tools for comparative proteomics analysis of sparse data sets with few experimental replicates

DEFF Research Database (Denmark)

Schwämmle, Veit; León, Ileana R.; Jensen, Ole Nørregaard

2013-01-01

Large-scale quantitative analyses of biological systems are often performed with few replicate experiments, leading to multiple nonidentical data sets due to missing values. For example, mass spectrometry driven proteomics experiments are frequently performed with few biological or technical...... replicates due to sample-scarcity or due to duty-cycle or sensitivity constraints, or limited capacity of the available instrumentation, leading to incomplete results where detection of significant feature changes becomes a challenge. This problem is further exacerbated for the detection of significant...... as a novel and optimal way to detect significantly changing features in these data sets. This approach is suitable for large quantitative data sets from stable isotope labeling and mass spectrometry experiments and should be applicable to large data sets of any type. An R script that implements the improved...

A quality improvement project using statistical process control methods for type 2 diabetes control in a resource-limited setting.

Science.gov (United States)

Flood, David; Douglas, Kate; Goldberg, Vera; Martinez, Boris; Garcia, Pablo; Arbour, MaryCatherine; Rohloff, Peter

2017-08-01

Quality improvement (QI) is a key strategy for improving diabetes care in low- and middle-income countries (LMICs). This study reports on a diabetes QI project in rural Guatemala whose primary aim was to improve glycemic control of a panel of adult diabetes patients. Formative research suggested multiple areas for programmatic improvement in ambulatory diabetes care. This project utilized the Model for Improvement and Agile Global Health, our organization's complementary healthcare implementation framework. A bundle of improvement activities were implemented at the home, clinic and institutional level. Control charts of mean hemoglobin A1C (HbA1C) and proportion of patients meeting target HbA1C showed improvement as special cause variation was identified 3 months after the intervention began. Control charts for secondary process measures offered insights into the value of different components of the intervention. Intensity of home-based diabetes education emerged as an important driver of panel glycemic control. Diabetes QI work is feasible in resource-limited settings in LMICs and can improve glycemic control. Statistical process control charts are a promising methodology for use with panels or registries of diabetes patients. © The Author 2017. Published by Oxford University Press in association with the International Society for Quality in Health Care. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

A multi-time-step noise reduction method for measuring velocity statistics from particle tracking velocimetry

Science.gov (United States)

Machicoane, Nathanaël; López-Caballero, Miguel; Bourgoin, Mickael; Aliseda, Alberto; Volk, Romain

2017-10-01

We present a method to improve the accuracy of velocity measurements for fluid flow or particles immersed in it, based on a multi-time-step approach that allows for cancellation of noise in the velocity measurements. Improved velocity statistics, a critical element in turbulent flow measurements, can be computed from the combination of the velocity moments computed using standard particle tracking velocimetry (PTV) or particle image velocimetry (PIV) techniques for data sets that have been collected over different values of time intervals between images. This method produces Eulerian velocity fields and Lagrangian velocity statistics with much lower noise levels compared to standard PIV or PTV measurements, without the need of filtering and/or windowing. Particle displacement between two frames is computed for multiple different time-step values between frames in a canonical experiment of homogeneous isotropic turbulence. The second order velocity structure function of the flow is computed with the new method and compared to results from traditional measurement techniques in the literature. Increased accuracy is also demonstrated by comparing the dissipation rate of turbulent kinetic energy measured from this function against previously validated measurements.

Efficacy, safety, and improved tolerability of travoprost BAK-free ophthalmic solution compared with prior prostaglandin therapy

Directory of Open Access Journals (Sweden)

J Charles Henry

2008-10-01

Full Text Available J Charles Henry1, James H Peace2, Jeanette A Stewart3,4, William C Stewart3,41Little Rock Eye Clinic, Little Rock, AR, USA; 2Diabetic Eye Medical Clinic, Inglewood, CA, USA; 3PRN Pharmaceutical Research Network, LLC, Dallas,TX, USA; 4Carolina Eye Institute, University of South Carolina, School of Medicine, Columbia, SC, USAPurpose: To evaluate the efficacy, safety and tolerability of changing to travoprost BAK-free from prior prostaglandin therapy in patients with primary open-angle glaucoma or ocular hypertension.Design: Prospective, multi-center, historical control study.Methods: Patients treated with latanoprost or bimatoprost who needed alternative therapy due to tolerability issues were enrolled. Patients were surveyed using the Ocular Surface Disease Index (OSDI to evaluate OSD symptoms prior to changing to travoprost BAK-free dosed once every evening. Patients were re-evaluated 3 months later.Results: In 691 patients, travoprost BAK-free demonstrated improved mean OSDI scores compared to either latanoprost or bimatoprost (p < 0.0001. Patients having any baseline OSD symptoms (n = 235 demonstrated significant improvement after switching to travoprost BAK-free (p < 0.0001. In 70.2% of these patients, symptoms were reduced in severity by at least 1 level. After changing medications to travoprost BAK-free, mean intraocular pressure (IOP was significantly decreased (p < 0.0001. Overall, 72.4% preferred travoprost BAK-free (p < 0.0001, travoprost BAK-free vs prior therapy. Travoprost BAK-free demonstrated less conjunctival hyperemia than either prior therapy (p < 0.0001.Conclusions: Patients previously treated with a BAK-preserved prostaglandin analog who are changed to travoprost BAK-free have clinically and statistically significant improvement in their OSD symptoms, decreased hyperemia, and equal or better IOP control.Keywords: glaucoma, prostaglandin analog, travoprost, latanoprost, bimatoprost, preservative, benzalkonium chloride

REANALYSIS OF F-STATISTIC GRAVITATIONAL-WAVE SEARCHES WITH THE HIGHER CRITICISM STATISTIC

International Nuclear Information System (INIS)

Bennett, M. F.; Melatos, A.; Delaigle, A.; Hall, P.

2013-01-01

We propose a new method of gravitational-wave detection using a modified form of higher criticism, a statistical technique introduced by Donoho and Jin. Higher criticism is designed to detect a group of sparse, weak sources, none of which are strong enough to be reliably estimated or detected individually. We apply higher criticism as a second-pass method to synthetic F-statistic and C-statistic data for a monochromatic periodic source in a binary system and quantify the improvement relative to the first-pass methods. We find that higher criticism on C-statistic data is more sensitive by ∼6% than the C-statistic alone under optimal conditions (i.e., binary orbit known exactly) and the relative advantage increases as the error in the orbital parameters increases. Higher criticism is robust even when the source is not monochromatic (e.g., phase-wandering in an accreting system). Applying higher criticism to a phase-wandering source over multiple time intervals gives a ∼> 30% increase in detectability with few assumptions about the frequency evolution. By contrast, in all-sky searches for unknown periodic sources, which are dominated by the brightest source, second-pass higher criticism does not provide any benefits over a first-pass search.

Comparative Statistical Mechanics of Muscle and Non-Muscle Contractile Systems: Stationary States of Near-Equilibrium Systems in A Linear Regime

Directory of Open Access Journals (Sweden)

Yves Lecarpentier

2017-10-01

Full Text Available A. Huxley’s equations were used to determine the mechanical properties of muscle myosin II (MII at the molecular level, as well as the probability of the occurrence of the different stages in the actin–myosin cycle. It was then possible to use the formalism of statistical mechanics with the grand canonical ensemble to calculate numerous thermodynamic parameters such as entropy, internal energy, affinity, thermodynamic flow, thermodynamic force, and entropy production rate. This allows us to compare the thermodynamic parameters of a non-muscle contractile system, such as the normal human placenta, with those of different striated skeletal muscles (soleus and extensor digitalis longus as well as the heart muscle and smooth muscles (trachea and uterus in the rat. In the human placental tissues, it was observed that the kinetics of the actin–myosin crossbridges were considerably slow compared with those of smooth and striated muscular systems. The entropy production rate was also particularly low in the human placental tissues, as compared with that observed in smooth and striated muscular systems. This is partly due to the low thermodynamic flow found in the human placental tissues. However, the unitary force of non-muscle myosin (NMII generated by each crossbridge cycle in the myofibroblasts of the human placental tissues was similar in magnitude to that of MII in the myocytes of both smooth and striated muscle cells. Statistical mechanics represents a powerful tool for studying the thermodynamics of all contractile muscle and non-muscle systems.

Against Inferential Statistics: How and Why Current Statistics Teaching Gets It Wrong

Science.gov (United States)

White, Patrick; Gorard, Stephen

2017-01-01

Recent concerns about a shortage of capacity for statistical and numerical analysis skills among social science students and researchers have prompted a range of initiatives aiming to improve teaching in this area. However, these projects have rarely re-evaluated the content of what is taught to students and have instead focussed primarily on…

Effect of Internet-Based Cognitive Apprenticeship Model (i-CAM on Statistics Learning among Postgraduate Students.

Directory of Open Access Journals (Sweden)

Farzaneh Saadati

Full Text Available Because students' ability to use statistics, which is mathematical in nature, is one of the concerns of educators, embedding within an e-learning system the pedagogical characteristics of learning is 'value added' because it facilitates the conventional method of learning mathematics. Many researchers emphasize the effectiveness of cognitive apprenticeship in learning and problem solving in the workplace. In a cognitive apprenticeship learning model, skills are learned within a community of practitioners through observation of modelling and then practice plus coaching. This study utilized an internet-based Cognitive Apprenticeship Model (i-CAM in three phases and evaluated its effectiveness for improving statistics problem-solving performance among postgraduate students. The results showed that, when compared to the conventional mathematics learning model, the i-CAM could significantly promote students' problem-solving performance at the end of each phase. In addition, the combination of the differences in students' test scores were considered to be statistically significant after controlling for the pre-test scores. The findings conveyed in this paper confirmed the considerable value of i-CAM in the improvement of statistics learning for non-specialized postgraduate students.

Nursing students' attitudes toward statistics: Effect of a biostatistics course and association with examination performance.

Science.gov (United States)

Kiekkas, Panagiotis; Panagiotarou, Aliki; Malja, Alvaro; Tahirai, Daniela; Zykai, Rountina; Bakalis, Nick; Stefanopoulos, Nikolaos

2015-12-01

Although statistical knowledge and skills are necessary for promoting evidence-based practice, health sciences students have expressed anxiety about statistics courses, which may hinder their learning of statistical concepts. To evaluate the effects of a biostatistics course on nursing students' attitudes toward statistics and to explore the association between these attitudes and their performance in the course examination. One-group quasi-experimental pre-test/post-test design. Undergraduate nursing students of the fifth or higher semester of studies, who attended a biostatistics course. Participants were asked to complete the pre-test and post-test forms of The Survey of Attitudes Toward Statistics (SATS)-36 scale at the beginning and end of the course respectively. Pre-test and post-test scale scores were compared, while correlations between post-test scores and participants' examination performance were estimated. Among 156 participants, post-test scores of the overall SATS-36 scale and of the Affect, Cognitive Competence, Interest and Effort components were significantly higher than pre-test ones, indicating that the course was followed by more positive attitudes toward statistics. Among 104 students who participated in the examination, higher post-test scores of the overall SATS-36 scale and of the Affect, Difficulty, Interest and Effort components were significantly but weakly correlated with higher examination performance. Students' attitudes toward statistics can be improved through appropriate biostatistics courses, while positive attitudes contribute to higher course achievements and possibly to improved statistical skills in later professional life. Copyright © 2015 Elsevier Ltd. All rights reserved.

Social indicators and other income statistics using the EUROMOD baseline: a comparison with Eurostat and National Statistics

OpenAIRE

Mantovani, Daniela; Sutherland, Holly

2003-01-01

This paper reports an exercise to validate EUROMOD output for 1998 by comparing income statistics calculated from the baseline micro-output with comparable statistics from other sources, including the European Community Household Panel. The main potential reasons for discrepancies are identified. While there are some specific national issues that arise, there are two main general points to consider in interpreting EUROMOD estimates of social indicators across EU member States: (a) the method ...

Statistical methods for improving verification of claims of origin for Italian wines based on stable isotope ratios

International Nuclear Information System (INIS)

Dordevic, N.; Wehrens, R.; Postma, G.J.; Buydens, L.M.C.; Camin, F.

2012-01-01

Highlights: ► The assessment of claims of origin is of enormous economic importance for DOC and DOCG wines. ► The official method is based on univariate statistical tests of H, C and O isotopic ratios. ► We consider 5220 Italian wine samples collected in the period 2000–2010. ► Multivariate statistical analysis leads to much better specificity and easier detection of false claims of origin. ► In the case of multi-modal data, mixture modelling provides additional improvements. - Abstract: Wine derives its economic value to a large extent from geographical origin, which has a significant impact on the quality of the wine. According to the food legislation, wines can be without geographical origin (table wine) and wines with origin. Wines with origin must have characteristics which are essential due to its region of production and must be produced, processed and prepared, exclusively within that region. The development of fast and reliable analytical methods for the assessment of claims of origin is very important. The current official method is based on the measurement of stable isotope ratios of water and alcohol in wine, which are influenced by climatic factors. The results in this paper are based on 5220 Italian wine samples collected in the period 2000–2010. We evaluate the univariate approach underlying the official method to assess claims of origin and propose several new methods to get better geographical discrimination between samples. It is shown that multivariate methods are superior to univariate approaches in that they show increased sensitivity and specificity. In cases where data are non-normally distributed, an approach based on mixture modelling provides additional improvements.

Probing NWP model deficiencies by statistical postprocessing

DEFF Research Database (Denmark)

Rosgaard, Martin Haubjerg; Nielsen, Henrik Aalborg; Nielsen, Torben S.

2016-01-01

The objective in this article is twofold. On one hand, a Model Output Statistics (MOS) framework for improved wind speed forecast accuracy is described and evaluated. On the other hand, the approach explored identifies unintuitive explanatory value from a diagnostic variable in an operational....... Based on the statistical model candidates inferred from the data, the lifted index NWP model diagnostic is consistently found among the NWP model predictors of the best performing statistical models across sites....

Basics of statistical physics

CERN Document Server

Müller-Kirsten, Harald J W

2013-01-01

Statistics links microscopic and macroscopic phenomena, and requires for this reason a large number of microscopic elements like atoms. The results are values of maximum probability or of averaging. This introduction to statistical physics concentrates on the basic principles, and attempts to explain these in simple terms supplemented by numerous examples. These basic principles include the difference between classical and quantum statistics, a priori probabilities as related to degeneracies, the vital aspect of indistinguishability as compared with distinguishability in classical physics, the differences between conserved and non-conserved elements, the different ways of counting arrangements in the three statistics (Maxwell-Boltzmann, Fermi-Dirac, Bose-Einstein), the difference between maximization of the number of arrangements of elements, and averaging in the Darwin-Fowler method. Significant applications to solids, radiation and electrons in metals are treated in separate chapters, as well as Bose-Eins...

R for statistics

CERN Document Server

Cornillon, Pierre-Andre; Husson, Francois; Jegou, Nicolas; Josse, Julie; Kloareg, Maela; Matzner-Lober, Eric; Rouviere, Laurent

2012-01-01

An Overview of RMain ConceptsInstalling RWork SessionHelpR ObjectsFunctionsPackagesExercisesPreparing DataReading Data from FileExporting ResultsManipulating VariablesManipulating IndividualsConcatenating Data TablesCross-TabulationExercisesR GraphicsConventional Graphical FunctionsGraphical Functions with latticeExercisesMaking Programs with RControl FlowsPredefined FunctionsCreating a FunctionExercisesStatistical MethodsIntroduction to the Statistical MethodsA Quick Start with RInstalling ROpening and Closing RThe Command PromptAttribution, Objects, and FunctionSelectionOther Rcmdr PackageImporting (or Inputting) DataGraphsStatistical AnalysisHypothesis TestConfidence Intervals for a MeanChi-Square Test of IndependenceComparison of Two MeansTesting Conformity of a ProportionComparing Several ProportionsThe Power of a TestRegressionSimple Linear RegressionMultiple Linear RegressionPartial Least Squares (PLS) RegressionAnalysis of Variance and CovarianceOne-Way Analysis of VarianceMulti-Way Analysis of Varian...

Statistical Model of Extreme Shear

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

2004-01-01

In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describe the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of high-sampled full-scale time series measurements...... are consistent, given the inevitabel uncertainties associated with model as well as with the extreme value data analysis. Keywords: Statistical model, extreme wind conditions, statistical analysis, turbulence, wind loading, statistical analysis, turbulence, wind loading, wind shear, wind turbines....

Statistical secrecy and multibit commitments

DEFF Research Database (Denmark)

Damgård, Ivan Bjerre; Pedersen, Torben P.; Pfitzmann, Birgit

1998-01-01

nothing about it. One definition is based on the L1-norm distance between probability distributions, the other on information theory. We prove that the two definitions are essentially equivalent. We also show that statistical counterparts of definitions of computational secrecy are essentially equivalent......We present and compare definitions of "statistically hiding" protocols, and we propose a novel statistically hiding commitment scheme. Informally, a protocol statistically hides a secret if a computationally unlimited adversary who conducts the protocol with the owner of the secret learns almost...... to our main definitions. Commitment schemes are an important cryptologic primitive. Their purpose is to commit one party to a certain value, while hiding this value from the other party until some later time. We present a statistically hiding commitment scheme allowing commitment to many bits...

Cardiac arrest risk standardization using administrative data compared to registry data.

Directory of Open Access Journals (Sweden)

Anne V Grossestreuer

Full Text Available Methods for comparing hospitals regarding cardiac arrest (CA outcomes, vital for improving resuscitation performance, rely on data collected by cardiac arrest registries. However, most CA patients are treated at hospitals that do not participate in such registries. This study aimed to determine whether CA risk standardization modeling based on administrative data could perform as well as that based on registry data.Two risk standardization logistic regression models were developed using 2453 patients treated from 2000-2015 at three hospitals in an academic health system. Registry and administrative data were accessed for all patients. The outcome was death at hospital discharge. The registry model was considered the "gold standard" with which to compare the administrative model, using metrics including comparing areas under the curve, calibration curves, and Bland-Altman plots. The administrative risk standardization model had a c-statistic of 0.891 (95% CI: 0.876-0.905 compared to a registry c-statistic of 0.907 (95% CI: 0.895-0.919. When limited to only non-modifiable factors, the administrative model had a c-statistic of 0.818 (95% CI: 0.799-0.838 compared to a registry c-statistic of 0.810 (95% CI: 0.788-0.831. All models were well-calibrated. There was no significant difference between c-statistics of the models, providing evidence that valid risk standardization can be performed using administrative data.Risk standardization using administrative data performs comparably to standardization using registry data. This methodology represents a new tool that can enable opportunities to compare hospital performance in specific hospital systems or across the entire US in terms of survival after CA.

Energy statistics yearbook 2002

International Nuclear Information System (INIS)

2005-01-01

The Energy Statistics Yearbook 2002 is a comprehensive collection of international energy statistics prepared by the United Nations Statistics Division. It is the forty-sixth in a series of annual compilations which commenced under the title World Energy Supplies in Selected Years, 1929-1950. It updates the statistical series shown in the previous issue. Supplementary series of monthly and quarterly data on production of energy may be found in the Monthly Bulletin of Statistics. The principal objective of the Yearbook is to provide a global framework of comparable data on long-term trends in the supply of mainly commercial primary and secondary forms of energy. Data for each type of fuel and aggregate data for the total mix of commercial fuels are shown for individual countries and areas and are summarized into regional and world totals. The data are compiled primarily from the annual energy questionnaire distributed by the United Nations Statistics Division and supplemented by official national statistical publications. Where official data are not available or are inconsistent, estimates are made by the Statistics Division based on governmental, professional or commercial materials. Estimates include, but are not limited to, extrapolated data based on partial year information, use of annual trends, trade data based on partner country reports, breakdowns of aggregated data as well as analysis of current energy events and activities

Energy statistics yearbook 2001

International Nuclear Information System (INIS)

2004-01-01

The Energy Statistics Yearbook 2001 is a comprehensive collection of international energy statistics prepared by the United Nations Statistics Division. It is the forty-fifth in a series of annual compilations which commenced under the title World Energy Supplies in Selected Years, 1929-1950. It updates the statistical series shown in the previous issue. Supplementary series of monthly and quarterly data on production of energy may be found in the Monthly Bulletin of Statistics. The principal objective of the Yearbook is to provide a global framework of comparable data on long-term trends in the supply of mainly commercial primary and secondary forms of energy. Data for each type of fuel and aggregate data for the total mix of commercial fuels are shown for individual countries and areas and are summarized into regional and world totals. The data are compiled primarily from the annual energy questionnaire distributed by the United Nations Statistics Division and supplemented by official national statistical publications. Where official data are not available or are inconsistent, estimates are made by the Statistics Division based on governmental, professional or commercial materials. Estimates include, but are not limited to, extrapolated data based on partial year information, use of annual trends, trade data based on partner country reports, breakdowns of aggregated data as well as analysis of current energy events and activities

Energy statistics yearbook 2000

International Nuclear Information System (INIS)

2002-01-01

The Energy Statistics Yearbook 2000 is a comprehensive collection of international energy statistics prepared by the United Nations Statistics Division. It is the forty-third in a series of annual compilations which commenced under the title World Energy Supplies in Selected Years, 1929-1950. It updates the statistical series shown in the previous issue. Supplementary series of monthly and quarterly data on production of energy may be found in the Monthly Bulletin of Statistics. The principal objective of the Yearbook is to provide a global framework of comparable data on long-term trends in the supply of mainly commercial primary and secondary forms of energy. Data for each type of fuel and aggregate data for the total mix of commercial fuels are shown for individual countries and areas and are summarized into regional and world totals. The data are compiled primarily from the annual energy questionnaire distributed by the United Nations Statistics Division and supplemented by official national statistical publications. Where official data are not available or are inconsistent, estimates are made by the Statistics Division based on governmental, professional or commercial materials. Estimates include, but are not limited to, extrapolated data based on partial year information, use of annual trends, trade data based on partner country reports, breakdowns of aggregated data as well as analysis of current energy events and activities

A robust statistical method for association-based eQTL analysis.

Directory of Open Access Journals (Sweden)

Ning Jiang

Full Text Available It has been well established that theoretical kernel for recently surging genome-wide association study (GWAS is statistical inference of linkage disequilibrium (LD between a tested genetic marker and a putative locus affecting a disease trait. However, LD analysis is vulnerable to several confounding factors of which population stratification is the most prominent. Whilst many methods have been proposed to correct for the influence either through predicting the structure parameters or correcting inflation in the test statistic due to the stratification, these may not be feasible or may impose further statistical problems in practical implementation.We propose here a novel statistical method to control spurious LD in GWAS from population structure by incorporating a control marker into testing for significance of genetic association of a polymorphic marker with phenotypic variation of a complex trait. The method avoids the need of structure prediction which may be infeasible or inadequate in practice and accounts properly for a varying effect of population stratification on different regions of the genome under study. Utility and statistical properties of the new method were tested through an intensive computer simulation study and an association-based genome-wide mapping of expression quantitative trait loci in genetically divergent human populations.The analyses show that the new method confers an improved statistical power for detecting genuine genetic association in subpopulations and an effective control of spurious associations stemmed from population structure when compared with other two popularly implemented methods in the literature of GWAS.

Fault Diagnosis for Rotating Machinery Using Vibration Measurement Deep Statistical Feature Learning

Directory of Open Access Journals (Sweden)

Chuan Li

2016-06-01

Full Text Available Fault diagnosis is important for the maintenance of rotating machinery. The detection of faults and fault patterns is a challenging part of machinery fault diagnosis. To tackle this problem, a model for deep statistical feature learning from vibration measurements of rotating machinery is presented in this paper. Vibration sensor signals collected from rotating mechanical systems are represented in the time, frequency, and time-frequency domains, each of which is then used to produce a statistical feature set. For learning statistical features, real-value Gaussian-Bernoulli restricted Boltzmann machines (GRBMs are stacked to develop a Gaussian-Bernoulli deep Boltzmann machine (GDBM. The suggested approach is applied as a deep statistical feature learning tool for both gearbox and bearing systems. The fault classification performances in experiments using this approach are 95.17% for the gearbox, and 91.75% for the bearing system. The proposed approach is compared to such standard methods as a support vector machine, GRBM and a combination model. In experiments, the best fault classification rate was detected using the proposed model. The results show that deep learning with statistical feature extraction has an essential improvement potential for diagnosing rotating machinery faults.

Fault Diagnosis for Rotating Machinery Using Vibration Measurement Deep Statistical Feature Learning.

Science.gov (United States)

Li, Chuan; Sánchez, René-Vinicio; Zurita, Grover; Cerrada, Mariela; Cabrera, Diego

2016-06-17

Fault diagnosis is important for the maintenance of rotating machinery. The detection of faults and fault patterns is a challenging part of machinery fault diagnosis. To tackle this problem, a model for deep statistical feature learning from vibration measurements of rotating machinery is presented in this paper. Vibration sensor signals collected from rotating mechanical systems are represented in the time, frequency, and time-frequency domains, each of which is then used to produce a statistical feature set. For learning statistical features, real-value Gaussian-Bernoulli restricted Boltzmann machines (GRBMs) are stacked to develop a Gaussian-Bernoulli deep Boltzmann machine (GDBM). The suggested approach is applied as a deep statistical feature learning tool for both gearbox and bearing systems. The fault classification performances in experiments using this approach are 95.17% for the gearbox, and 91.75% for the bearing system. The proposed approach is compared to such standard methods as a support vector machine, GRBM and a combination model. In experiments, the best fault classification rate was detected using the proposed model. The results show that deep learning with statistical feature extraction has an essential improvement potential for diagnosing rotating machinery faults.

IBM SPSS statistics 19 made simple

CERN Document Server

Gray, Colin D

2012-01-01

This new edition of one of the most widely read textbooks in its field introduces the reader to data analysis with the most powerful and versatile statistical package on the market: IBM SPSS Statistics 19. Each new release of SPSS Statistics features new options and other improvements. There remains a core of fundamental operating principles and techniques which have continued to apply to all releases issued in recent years and have been proved to be worth communicating in a small volume. This practical and informal book combines simplicity and clarity of presentation with a comprehensive trea

Comparison of climate envelope models developed using expert-selected variables versus statistical selection

Science.gov (United States)

Brandt, Laura A.; Benscoter, Allison; Harvey, Rebecca G.; Speroterra, Carolina; Bucklin, David N.; Romañach, Stephanie; Watling, James I.; Mazzotti, Frank J.

2017-01-01

Climate envelope models are widely used to describe potential future distribution of species under different climate change scenarios. It is broadly recognized that there are both strengths and limitations to using climate envelope models and that outcomes are sensitive to initial assumptions, inputs, and modeling methods Selection of predictor variables, a central step in modeling, is one of the areas where different techniques can yield varying results. Selection of climate variables to use as predictors is often done using statistical approaches that develop correlations between occurrences and climate data. These approaches have received criticism in that they rely on the statistical properties of the data rather than directly incorporating biological information about species responses to temperature and precipitation. We evaluated and compared models and prediction maps for 15 threatened or endangered species in Florida based on two variable selection techniques: expert opinion and a statistical method. We compared model performance between these two approaches for contemporary predictions, and the spatial correlation, spatial overlap and area predicted for contemporary and future climate predictions. In general, experts identified more variables as being important than the statistical method and there was low overlap in the variable sets (0.9 for area under the curve (AUC) and >0.7 for true skill statistic (TSS). Spatial overlap, which compares the spatial configuration between maps constructed using the different variable selection techniques, was only moderate overall (about 60%), with a great deal of variability across species. Difference in spatial overlap was even greater under future climate projections, indicating additional divergence of model outputs from different variable selection techniques. Our work is in agreement with other studies which have found that for broad-scale species distribution modeling, using statistical methods of variable

Statistical methods for decision making in mine action

DEFF Research Database (Denmark)

Larsen, Jan

The lecture discusses the basics of statistical decision making in connection with humanitarian mine action. There is special focus on: 1) requirements for mine detection; 2) design and evaluation of mine equipment; 3) performance improvement by statistical learning and information fusion; 4...

Statistical modelling for ship propulsion efficiency

DEFF Research Database (Denmark)

Petersen, Jóan Petur; Jacobsen, Daniel J.; Winther, Ole

2012-01-01

This paper presents a state-of-the-art systems approach to statistical modelling of fuel efficiency in ship propulsion, and also a novel and publicly available data set of high quality sensory data. Two statistical model approaches are investigated and compared: artificial neural networks...

Improving education under work-hour restrictions: comparing learning and teaching preferences of faculty, residents, and students.

Science.gov (United States)

Jack, Megan C; Kenkare, Sonya B; Saville, Benjamin R; Beidler, Stephanie K; Saba, Sam C; West, Alisha N; Hanemann, Michael S; van Aalst, John A

2010-01-01

Faced with work-hour restrictions, educators are mandated to improve the efficiency of resident and medical student education. Few studies have assessed learning styles in medicine; none have compared teaching and learning preferences. Validated tools exist to study these deficiencies. Kolb describes 4 learning styles: converging (practical), diverging (imaginative), assimilating (inductive), and accommodating (active). Grasha Teaching Styles are categorized into "clusters": 1 (teacher-centered, knowledge acquisition), 2 (teacher-centered, role modeling), 3 (student-centered, problem-solving), and 4 (student-centered, facilitative). Kolb's Learning Style Inventory (HayGroup, Philadelphia, Pennsylvania) and Grasha-Riechmann's TSS were administered to surgical faculty (n = 61), residents (n = 96), and medical students (n = 183) at a tertiary academic medical center, after informed consent was obtained (IRB # 06-0612). Statistical analysis was performed using χ(2) and Fisher exact tests. Surgical residents preferred active learning (p = 0.053), whereas faculty preferred reflective learning (p style more often than surgical faculty (p = 0.01). Medical students preferred converging learning (42%) and cluster 4 teaching (35%). Statistical significance was unchanged when corrected for gender, resident training level, and subspecialization. Significant differences exist between faculty and residents in both learning and teaching preferences; this finding suggests inefficiency in resident education, as previous research suggests that learning styles parallel teaching styles. Absence of a predominant teaching style in residents suggests these individuals are learning to be teachers. The adaptation of faculty teaching methods to account for variations in resident learning styles may promote a better learning environment and more efficient faculty-resident interaction. Additional, multi-institutional studies using these tools are needed to elucidate these findings fully

Second Language Experience Facilitates Statistical Learning of Novel Linguistic Materials.

Science.gov (United States)

Potter, Christine E; Wang, Tianlin; Saffran, Jenny R

2017-04-01

Recent research has begun to explore individual differences in statistical learning, and how those differences may be related to other cognitive abilities, particularly their effects on language learning. In this research, we explored a different type of relationship between language learning and statistical learning: the possibility that learning a new language may also influence statistical learning by changing the regularities to which learners are sensitive. We tested two groups of participants, Mandarin Learners and Naïve Controls, at two time points, 6 months apart. At each time point, participants performed two different statistical learning tasks: an artificial tonal language statistical learning task and a visual statistical learning task. Only the Mandarin-learning group showed significant improvement on the linguistic task, whereas both groups improved equally on the visual task. These results support the view that there are multiple influences on statistical learning. Domain-relevant experiences may affect the regularities that learners can discover when presented with novel stimuli. Copyright © 2016 Cognitive Science Society, Inc.

Statistical methods in nuclear theory

International Nuclear Information System (INIS)

Shubin, Yu.N.

1974-01-01

The paper outlines statistical methods which are widely used for describing properties of excited states of nuclei and nuclear reactions. It discusses physical assumptions lying at the basis of known distributions between levels (Wigner, Poisson distributions) and of widths of highly excited states (Porter-Thomas distribution, as well as assumptions used in the statistical theory of nuclear reactions and in the fluctuation analysis. The author considers the random matrix method, which consists in replacing the matrix elements of a residual interaction by random variables with a simple statistical distribution. Experimental data are compared with results of calculations using the statistical model. The superfluid nucleus model is considered with regard to superconducting-type pair correlations

To improve the quality of the statistical analysis of papers published in the Journal of the Korean Society for Therapeutic Radiology and Oncology

International Nuclear Information System (INIS)

Park, Hee Chul; Choi, Doo Ho; Ahn, Song Vogue

2008-01-01

To improve the quality of the statistical analysis of papers published in the Journal of the Korean Society for Therapeutic Radiology and Oncology (JKOSTRO) by evaluating commonly encountered errors. Materials and Methods: Papers published in the JKOSTRO from January 2006 to December 2007 were reviewed for methodological and statistical validity using a modified version of Ahn's checklist. A statistician reviewed individual papers and evaluated the list items in the checklist for each paper. To avoid the potential assessment error by the statistician who lacks expertise in the field of radiation oncology; the editorial board of the JKOSTRO reviewed each checklist for individual articles. A frequency analysis of the list items was performed using SAS (version 9.0, SAS Institute, NC, USA) software. Results: A total of 73 papers including 5 case reports and 68 original articles were reviewed. Inferential statistics was used in 46 papers. The most commonly adopted statistical methodology was a survival analysis (58.7%). Only 19% of papers were free of statistical errors. Errors of omission were encountered in 34 (50.0%) papers. Errors of commission were encountered in 35 (51.5%) papers. Twenty-one papers (30.9%) had both errors of omission and commission. Conclusion: A variety of statistical errors were encountered in papers published in the JKOSTRO. The current study suggests that a more thorough review of the statistical analysis is needed for manuscripts submitted in the JKOSTRO

PRECISE:PRivacy-prEserving Cloud-assisted quality Improvement Service in hEalthcare.

Science.gov (United States)

Chen, Feng; Wang, Shuang; Mohammed, Noman; Cheng, Samuel; Jiang, Xiaoqian

2014-10-01

Quality improvement (QI) requires systematic and continuous efforts to enhance healthcare services. A healthcare provider might wish to compare local statistics with those from other institutions in order to identify problems and develop intervention to improve the quality of care. However, the sharing of institution information may be deterred by institutional privacy as publicizing such statistics could lead to embarrassment and even financial damage. In this article, we propose a PRivacy-prEserving Cloud-assisted quality Improvement Service in hEalthcare (PRECISE), which aims at enabling cross-institution comparison of healthcare statistics while protecting privacy. The proposed framework relies on a set of state-of-the-art cryptographic protocols including homomorphic encryption and Yao's garbled circuit schemes. By securely pooling data from different institutions, PRECISE can rank the encrypted statistics to facilitate QI among participating institutes. We conducted experiments using MIMIC II database and demonstrated the feasibility of the proposed PRECISE framework.

Multivariate Statistical Process Control

DEFF Research Database (Denmark)

Kulahci, Murat

2013-01-01

As sensor and computer technology continues to improve, it becomes a normal occurrence that we confront with high dimensional data sets. As in many areas of industrial statistics, this brings forth various challenges in statistical process control (SPC) and monitoring for which the aim...... is to identify “out-of-control” state of a process using control charts in order to reduce the excessive variation caused by so-called assignable causes. In practice, the most common method of monitoring multivariate data is through a statistic akin to the Hotelling’s T2. For high dimensional data with excessive...... amount of cross correlation, practitioners are often recommended to use latent structures methods such as Principal Component Analysis to summarize the data in only a few linear combinations of the original variables that capture most of the variation in the data. Applications of these control charts...

An improved mixing model providing joint statistics of scalar and scalar dissipation

Energy Technology Data Exchange (ETDEWEB)

Meyer, Daniel W. [Department of Energy Resources Engineering, Stanford University, Stanford, CA (United States); Jenny, Patrick [Institute of Fluid Dynamics, ETH Zurich (Switzerland)

2008-11-15

For the calculation of nonpremixed turbulent flames with thin reaction zones the joint probability density function (PDF) of the mixture fraction and its dissipation rate plays an important role. The corresponding PDF transport equation involves a mixing model for the closure of the molecular mixing term. Here, the parameterized scalar profile (PSP) mixing model is extended to provide the required joint statistics. Model predictions are validated using direct numerical simulation (DNS) data of a passive scalar mixing in a statistically homogeneous turbulent flow. Comparisons between the DNS and the model predictions are provided, which involve different initial scalar-field lengthscales. (author)

Humans make efficient use of natural image statistics when performing spatial interpolation.

Science.gov (United States)

D'Antona, Anthony D; Perry, Jeffrey S; Geisler, Wilson S

2013-12-16

Visual systems learn through evolution and experience over the lifespan to exploit the statistical structure of natural images when performing visual tasks. Understanding which aspects of this statistical structure are incorporated into the human nervous system is a fundamental goal in vision science. To address this goal, we measured human ability to estimate the intensity of missing image pixels in natural images. Human estimation accuracy is compared with various simple heuristics (e.g., local mean) and with optimal observers that have nearly complete knowledge of the local statistical structure of natural images. Human estimates are more accurate than those of simple heuristics, and they match the performance of an optimal observer that knows the local statistical structure of relative intensities (contrasts). This optimal observer predicts the detailed pattern of human estimation errors and hence the results place strong constraints on the underlying neural mechanisms. However, humans do not reach the performance of an optimal observer that knows the local statistical structure of the absolute intensities, which reflect both local relative intensities and local mean intensity. As predicted from a statistical analysis of natural images, human estimation accuracy is negligibly improved by expanding the context from a local patch to the whole image. Our results demonstrate that the human visual system exploits efficiently the statistical structure of natural images.

Study of the effects of photoelectron statistics on Thomson scattering data

International Nuclear Information System (INIS)

Hart, G.W.; Levinton, F.M.; McNeill, D.H.

1986-01-01

A computer code has been developed which simulates a Thomson scattering measurement, from the counting statistics of the input channels through the mathematical analysis of the data. The scattered and background signals in each of the wavelength channels are assumed to obey Poisson statistics, and the spectral data are fitted to a Gaussian curve using a nonlinear least-squares fitting algorithm. This method goes beyond the usual calculation of the signal-to-noise ratio for the hardware and gives a quantitative measure of the effect of the noise on the final measurement. This method is applicable to Thomson scattering measurements in which the signal-to-noise ratio is low due to either low signal or high background. Thomson scattering data from the S-1 spheromak have been compared to this simulation, and they have been found to be in good agreement. This code has proven to be useful in assessing the effects of counting statistics relative to shot-to-shot variability in producing the observed spread in the data. It was also useful for designing improvements for the S-1 Thomson scattering system, and this method would be applicable to any measurement affected by counting statistics

IGESS: a statistical approach to integrating individual-level genotype data and summary statistics in genome-wide association studies.

Science.gov (United States)

Dai, Mingwei; Ming, Jingsi; Cai, Mingxuan; Liu, Jin; Yang, Can; Wan, Xiang; Xu, Zongben

2017-09-15

Results from genome-wide association studies (GWAS) suggest that a complex phenotype is often affected by many variants with small effects, known as 'polygenicity'. Tens of thousands of samples are often required to ensure statistical power of identifying these variants with small effects. However, it is often the case that a research group can only get approval for the access to individual-level genotype data with a limited sample size (e.g. a few hundreds or thousands). Meanwhile, summary statistics generated using single-variant-based analysis are becoming publicly available. The sample sizes associated with the summary statistics datasets are usually quite large. How to make the most efficient use of existing abundant data resources largely remains an open question. In this study, we propose a statistical approach, IGESS, to increasing statistical power of identifying risk variants and improving accuracy of risk prediction by i ntegrating individual level ge notype data and s ummary s tatistics. An efficient algorithm based on variational inference is developed to handle the genome-wide analysis. Through comprehensive simulation studies, we demonstrated the advantages of IGESS over the methods which take either individual-level data or summary statistics data as input. We applied IGESS to perform integrative analysis of Crohns Disease from WTCCC and summary statistics from other studies. IGESS was able to significantly increase the statistical power of identifying risk variants and improve the risk prediction accuracy from 63.2% ( ±0.4% ) to 69.4% ( ±0.1% ) using about 240 000 variants. The IGESS software is available at https://github.com/daviddaigithub/IGESS . zbxu@xjtu.edu.cn or xwan@comp.hkbu.edu.hk or eeyang@hkbu.edu.hk. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Explorations in Statistics: Hypothesis Tests and P Values

Science.gov (United States)

Curran-Everett, Douglas

2009-01-01

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

Statistical methods for improving verification of claims of origin for Italian wines based on stable isotope ratios

Energy Technology Data Exchange (ETDEWEB)

Dordevic, N.; Wehrens, R. [IASMA Research and Innovation Centre, Fondazione Edmund Mach, via Mach 1, 38010 San Michele all' Adige (Italy); Postma, G.J.; Buydens, L.M.C. [Radboud University Nijmegen, Institute for Molecules and Materials, Analytical Chemistry, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Camin, F., E-mail: federica.camin@fmach.it [IASMA Research and Innovation Centre, Fondazione Edmund Mach, via Mach 1, 38010 San Michele all' Adige (Italy)

2012-12-13

Highlights: Black-Right-Pointing-Pointer The assessment of claims of origin is of enormous economic importance for DOC and DOCG wines. Black-Right-Pointing-Pointer The official method is based on univariate statistical tests of H, C and O isotopic ratios. Black-Right-Pointing-Pointer We consider 5220 Italian wine samples collected in the period 2000-2010. Black-Right-Pointing-Pointer Multivariate statistical analysis leads to much better specificity and easier detection of false claims of origin. Black-Right-Pointing-Pointer In the case of multi-modal data, mixture modelling provides additional improvements. - Abstract: Wine derives its economic value to a large extent from geographical origin, which has a significant impact on the quality of the wine. According to the food legislation, wines can be without geographical origin (table wine) and wines with origin. Wines with origin must have characteristics which are essential due to its region of production and must be produced, processed and prepared, exclusively within that region. The development of fast and reliable analytical methods for the assessment of claims of origin is very important. The current official method is based on the measurement of stable isotope ratios of water and alcohol in wine, which are influenced by climatic factors. The results in this paper are based on 5220 Italian wine samples collected in the period 2000-2010. We evaluate the univariate approach underlying the official method to assess claims of origin and propose several new methods to get better geographical discrimination between samples. It is shown that multivariate methods are superior to univariate approaches in that they show increased sensitivity and specificity. In cases where data are non-normally distributed, an approach based on mixture modelling provides additional improvements.

Statistical Methods for Unusual Count Data

DEFF Research Database (Denmark)

Guthrie, Katherine A.; Gammill, Hilary S.; Kamper-Jørgensen, Mads

2016-01-01

microchimerism data present challenges for statistical analysis, including a skewed distribution, excess zero values, and occasional large values. Methods for comparing microchimerism levels across groups while controlling for covariates are not well established. We compared statistical models for quantitative...... microchimerism values, applied to simulated data sets and 2 observed data sets, to make recommendations for analytic practice. Modeling the level of quantitative microchimerism as a rate via Poisson or negative binomial model with the rate of detection defined as a count of microchimerism genome equivalents per...

Improvement in Activities of Daily Living among Danish Centenarians?

DEFF Research Database (Denmark)

Rasmussen, Signe Høi; Thinggaard, Mikael; Højgaard, Majken Boris

2018-01-01

of the latest cohort used assistive devices than the former (statistically significant for the majority of assistive devices). Conclusion: This comparative study shows improvements in reported ADL in the later born cohort of centenarians, even though only significant among women. As women constitute...

Renyi statistics in equilibrium statistical mechanics

International Nuclear Information System (INIS)

Parvan, A.S.; Biro, T.S.

2010-01-01

The Renyi statistics in the canonical and microcanonical ensembles is examined both in general and in particular for the ideal gas. In the microcanonical ensemble the Renyi statistics is equivalent to the Boltzmann-Gibbs statistics. By the exact analytical results for the ideal gas, it is shown that in the canonical ensemble, taking the thermodynamic limit, the Renyi statistics is also equivalent to the Boltzmann-Gibbs statistics. Furthermore it satisfies the requirements of the equilibrium thermodynamics, i.e. the thermodynamical potential of the statistical ensemble is a homogeneous function of first degree of its extensive variables of state. We conclude that the Renyi statistics arrives at the same thermodynamical relations, as those stemming from the Boltzmann-Gibbs statistics in this limit.

Spatial statistics of pitting corrosion patterning: Quadrat counts and the non-homogeneous Poisson process

International Nuclear Information System (INIS)

Lopez de la Cruz, J.; Gutierrez, M.A.

2008-01-01

This paper presents a stochastic analysis of spatial point patterns as effect of localized pitting corrosion. The Quadrat Counts method is studied with two empirical pit patterns. The results are dependent on the quadrat size and bias is introduced when empty quadrats are accounted for the analysis. The spatially inhomogeneous Poisson process is used to improve the performance of the Quadrat Counts method. The latter combines Quadrat Counts with distance-based statistics in the analysis of pit patterns. The Inter-Event and the Nearest-Neighbour statistics are here implemented in order to compare their results. Further, the treatment of patterns in irregular domains is discussed

Spontaneous improvement in randomised clinical trials: meta-analysis of three-armed trials comparing no treatment, placebo and active intervention

DEFF Research Database (Denmark)

Krogsbøll, Lasse Theis; Hróbjartsson, Asbjørn; Gøtzsche, Peter C

2009-01-01

were psychological in 17 trials, physical in 15 trials, and pharmacological in 5 trials. Overall, across all conditions and interventions, there was a statistically significant change from baseline in all three arms. The standardized mean difference (SMD) for change from baseline was -0.24 (95...... uncertainty, as indicated by the confidence intervals for the three SMDs. The conditions that had the most pronounced spontaneous improvement were nausea (45%), smoking (40%), depression (35%), phobia (34%) and acute pain (25%). CONCLUSION: Spontaneous improvement and effect of placebo contributed importantly...

Strategies for improving utilization of computerized statistical data by the social science community.

OpenAIRE

Robbin, Alice

1981-01-01

In recent decades there has been a notable expansion of statistical data produced by the public and private sectors for administrative, research, policy and evaluation programs. This is due to advances in relatively inexpensive and efficient data collection and management of computer-readable statistical data. Corresponding changes have not occurred in the management of data collection, preservation, description and dissemination. As a result, the process by which data become accessible to so...

Improved parameterization of managed grassland in a global process-based vegetation model using Bayesian statistics

Science.gov (United States)

Rolinski, S.; Müller, C.; Lotze-Campen, H.; Bondeau, A.

2010-12-01

More than a quarter of the Earth’s land surface is covered by grassland, which is also the major part (~ 70 %) of the agricultural area. Most of this area is used for livestock production in different degrees of intensity. The dynamic global vegetation model LPJmL (Sitch et al., Global Change Biology, 2003; Bondeau et al., Global Change Biology, 2007) is one of few process-based model that simulates biomass production on managed grasslands at the global scale. The implementation of managed grasslands and its evaluation has received little attention so far, as reference data on grassland productivity are scarce and the definition of grassland extent and usage are highly uncertain. However, grassland productivity is related to large areas, and strongly influences global estimates of carbon and water budgets and should thus be improved. Plants are implemented in LPJmL in an aggregated form as plant functional types assuming that processes concerning carbon and water fluxes are quite similar between species of the same type. Therefore, the parameterization of a functional type is possible with parameters in a physiologically meaningful range of values. The actual choice of the parameter values from the possible and reasonable phase space should satisfy the condition of the best fit of model results and measured data. In order to improve the parameterization of managed grass we follow a combined procedure using model output and measured data of carbon and water fluxes. By comparing carbon and water fluxes simultaneously, we expect well-balanced refinements and avoid over-tuning of the model in only one direction. The comparison of annual biomass from grassland to data from the Food and Agriculture Organization of the United Nations (FAO) per country provide an overview about the order of magnitude and the identification of deviations. The comparison of daily net primary productivity, soil respiration and water fluxes at specific sites (FluxNet Data) provides

Statistical data filtration in neutron coincidence counting

International Nuclear Information System (INIS)

Beddingfield, D.H.; Menlove, H.O.

1992-11-01

We assessed the effectiveness of statistical data filtration to minimize the contribution of matrix materials in 200-ell drums to the nondestructive assay of plutonium. Those matrices were examined: polyethylene, concrete, aluminum, iron, cadmium, and lead. Statistical filtration of neutron coincidence data improved the low-end sensitivity of coincidence counters. Spurious data arising from electrical noise, matrix spallation, and geometric effects were smoothed in a predictable fashion by the statistical filter. The filter effectively lowers the minimum detectable mass limit that can be achieved for plutonium assay using passive neutron coincidence counting

Statistical shape analysis with applications in R

CERN Document Server

Dryden, Ian L

2016-01-01

A thoroughly revised and updated edition of this introduction to modern statistical methods for shape analysis Shape analysis is an important tool in the many disciplines where objects are compared using geometrical features. Examples include comparing brain shape in schizophrenia; investigating protein molecules in bioinformatics; and describing growth of organisms in biology. This book is a significant update of the highly-regarded `Statistical Shape Analysis’ by the same authors. The new edition lays the foundations of landmark shape analysis, including geometrical concepts and statistical techniques, and extends to include analysis of curves, surfaces, images and other types of object data. Key definitions and concepts are discussed throughout, and the relative merits of different approaches are presented. The authors have included substantial new material on recent statistical developments and offer numerous examples throughout the text. Concepts are introduced in an accessible manner, while reta...

Statistical criteria for characterizing irradiance time series.

Energy Technology Data Exchange (ETDEWEB)

Stein, Joshua S.; Ellis, Abraham; Hansen, Clifford W.

2010-10-01

We propose and examine several statistical criteria for characterizing time series of solar irradiance. Time series of irradiance are used in analyses that seek to quantify the performance of photovoltaic (PV) power systems over time. Time series of irradiance are either measured or are simulated using models. Simulations of irradiance are often calibrated to or generated from statistics for observed irradiance and simulations are validated by comparing the simulation output to the observed irradiance. Criteria used in this comparison should derive from the context of the analyses in which the simulated irradiance is to be used. We examine three statistics that characterize time series and their use as criteria for comparing time series. We demonstrate these statistics using observed irradiance data recorded in August 2007 in Las Vegas, Nevada, and in June 2009 in Albuquerque, New Mexico.

Improvements of ENSO-monsoon relationship in CMIP5 models through statistical downscaling over India.

Science.gov (United States)

Akhter, J.; Das, L.; Deb, A.

2017-12-01

Present study has assessed the skills of global climate models (GCMS) from coupled model inter-comparison project phase five (CMIP5) in simulating ENSO-monsoon relationships over seven homogeneous zones of India. Observational sea surface temperature (SST) data has revealed that there has been a significant negative correlation between zonal precipitation and Nino 3.4 index over North Mountainous India, North West India, North Central India, West Peninsular India and South Peninsular India. First and third principal component (PC) of zonal precipitation explaining 44.4% and 14.2% variance respectively has also shown significant anti-correlation with Nino 3.4. Analysis with CMIP5 models revealed that majority of GCMs have failed to reproduce both magnitude and phase of such relationships mainly due to poor simulation of Nino 3.4 index. Therefore, an attempt has been made to improve the results through empirical orthogonal function (EOF) based statistical downscaling of CMIP5 GCMs. To downscale Nino 3.4 index, an optimal predictor combination of PCs extracted from EOF fields of large scale GCM predictors like Geo-potential height, u and v wind, Specific and relative humidity and air temperature at pressure levels 500, 850 and 1000 hpa, mean sea level pressure and atmospheric vapor content has been utilized. Results indicated improvements of downscaled CMIP5 models in simulating ENSO-monsoon relationship for zone wise precipitation. Multi-model ensemble (MME) of downscaled GCMs has better skill than individuals GCM. Therefore, downscaled MME may be used more reliably to investigate future ENSO-monsoon relationship under various warming scenarios

Cranial CT with adaptive statistical iterative reconstruction: improved image quality with concomitant radiation dose reduction.

Science.gov (United States)

Rapalino, O; Kamalian, Shervin; Kamalian, Shahmir; Payabvash, S; Souza, L C S; Zhang, D; Mukta, J; Sahani, D V; Lev, M H; Pomerantz, S R

2012-04-01

To safeguard patient health, there is great interest in CT radiation-dose reduction. The purpose of this study was to evaluate the impact of an iterative-reconstruction algorithm, ASIR, on image-quality measures in reduced-dose head CT scans for adult patients. Using a 64-section scanner, we analyzed 100 reduced-dose adult head CT scans at 6 predefined levels of ASIR blended with FBP reconstruction. These scans were compared with 50 CT scans previously obtained at a higher routine dose without ASIR reconstruction. SNR and CNR were computed from Hounsfield unit measurements of normal GM and WM of brain parenchyma. A blinded qualitative analysis was performed in 10 lower-dose CT datasets compared with higher-dose ones without ASIR. Phantom data analysis was also performed. Lower-dose scans without ASIR had significantly lower mean GM and WM SNR (P = .003) and similar GM-WM CNR values compared with higher routine-dose scans. However, at ASIR levels of 20%-40%, there was no statistically significant difference in SNR, and at ASIR levels of ≥60%, the SNR values of the reduced-dose scans were significantly higher (P ASIR levels of ≥40% (P ASIR levels ≥60% (P ASIR in adult head CT scans reduces image noise and increases low-contrast resolution, while allowing lower radiation doses without affecting spatial resolution.

Difficult cases for chromosomal dosimetry: Statistical considerations

Energy Technology Data Exchange (ETDEWEB)

Vinnikov, Volodymyr A., E-mail: vlad.vinnikov@mail.ru [Grigoriev Institute for Medical Radiology of the National Academy of Medical Science of Ukraine, Pushkinskaya Street 82, Kharkiv 61024 (Ukraine); Ainsbury, Elizabeth A., E-mail: liz.ainsbury@hpa.org.uk [Health Protection Agency, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxon OX11 0RQ (United Kingdom); Lloyd, David C., E-mail: david.lloyd@hpa.org.uk [Health Protection Agency, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxon OX11 0RQ (United Kingdom); Maznyk, Nataliya A., E-mail: maznik.cytogen@mail.ru [Grigoriev Institute for Medical Radiology of the National Academy of Medical Science of Ukraine, Pushkinskaya Street 82, Kharkiv 61024 (Ukraine); Rothkamm, Kai, E-mail: kai.rothkamm@hpa.org.uk [Health Protection Agency, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxon OX11 0RQ (United Kingdom)

2011-09-15

Several examples are selected from the literature in order to illustrate combinations of complicating factors, which may occur in real-life radiation exposure scenarios that affect the accuracy of cytogenetic dose estimates. An analysis of limitations in the current statistical methods used in biodosimetry was carried out. Possible directions for further improvement of the statistical basis of chromosomal dosimetry by specific mathematical procedures are outlined.

BrightStat.com: free statistics online.

Science.gov (United States)

Stricker, Daniel

2008-10-01

Powerful software for statistical analysis is expensive. Here I present BrightStat, a statistical software running on the Internet which is free of charge. BrightStat's goals, its main capabilities and functionalities are outlined. Three different sample runs, a Friedman test, a chi-square test, and a step-wise multiple regression are presented. The results obtained by BrightStat are compared with results computed by SPSS, one of the global leader in providing statistical software, and VassarStats, a collection of scripts for data analysis running on the Internet. Elementary statistics is an inherent part of academic education and BrightStat is an alternative to commercial products.

Pain and functional outcome after vertebroplasty and kyphoplasty. A comparative study

International Nuclear Information System (INIS)

Ruiz Santiago, Fernando; Perez Abela, Antonio; Guzman Alvarez, Luis; Alvarez Osuna, Rosa Maria; Mar Castellano Garcia, Maria del

2010-01-01

Purpose: The aim of this study was to compare the effectiveness of percutaneous vertebroplasty and kyphoplasty to treat pain from non-neoplastic vertebral fractures and improve functional outcomes. Materials and methods: We compared 30 patients treated by vertebroplasty for non-neoplastic vertebral fractures with 30 patients treated by kyphoplasty for the same condition. Pain was measured with a visual analogue scale (VAS) and functional outcome with the Oswestry disability index (ODI). Baseline data were compared with measurements on the day after the procedure (for pain alone) and at 1 month, 6 months, and 1 year. Results: The VAS pain score was reduced by 4-5 points on the day after either type of treatment, a statistically significant improvement. The global ODI was significantly improved (by 13-18 points) at 1 month after either procedure. These improvements persisted at 6 months and 1 year. No significant differences in functional outcome were observed between the techniques. Conclusion: Vertebroplasty and kyphoplasty obtain similar improvements in pain and functional outcomes in these patients. The choice of technique must therefore depend on other factors. An initial improvement with either technique is a good predictor of long-term improvement.

Pain and functional outcome after vertebroplasty and kyphoplasty. A comparative study

Energy Technology Data Exchange (ETDEWEB)

Ruiz Santiago, Fernando, E-mail: ferusan@ono.co [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18014 Granada (Spain); Perez Abela, Antonio [Department of Traumatology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18014 Granada (Spain); Guzman Alvarez, Luis [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18014 Granada Spain (Spain); Alvarez Osuna, Rosa Maria [Department of Traumatology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18014 Granada (Spain); Mar Castellano Garcia, Maria del [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18014 Granada (Spain)

2010-08-15

Purpose: The aim of this study was to compare the effectiveness of percutaneous vertebroplasty and kyphoplasty to treat pain from non-neoplastic vertebral fractures and improve functional outcomes. Materials and methods: We compared 30 patients treated by vertebroplasty for non-neoplastic vertebral fractures with 30 patients treated by kyphoplasty for the same condition. Pain was measured with a visual analogue scale (VAS) and functional outcome with the Oswestry disability index (ODI). Baseline data were compared with measurements on the day after the procedure (for pain alone) and at 1 month, 6 months, and 1 year. Results: The VAS pain score was reduced by 4-5 points on the day after either type of treatment, a statistically significant improvement. The global ODI was significantly improved (by 13-18 points) at 1 month after either procedure. These improvements persisted at 6 months and 1 year. No significant differences in functional outcome were observed between the techniques. Conclusion: Vertebroplasty and kyphoplasty obtain similar improvements in pain and functional outcomes in these patients. The choice of technique must therefore depend on other factors. An initial improvement with either technique is a good predictor of long-term improvement.

Possible future changes in South East Australian frost frequency: an inter-comparison of statistical downscaling approaches

Science.gov (United States)

Crimp, Steven; Jin, Huidong; Kokic, Philip; Bakar, Shuvo; Nicholls, Neville

2018-04-01

Anthropogenic climate change has already been shown to effect the frequency, intensity, spatial extent, duration and seasonality of extreme climate events. Understanding these changes is an important step in determining exposure, vulnerability and focus for adaptation. In an attempt to support adaptation decision-making we have examined statistical modelling techniques to improve the representation of global climate model (GCM) derived projections of minimum temperature extremes (frosts) in Australia. We examine the spatial changes in minimum temperature extreme metrics (e.g. monthly and seasonal frost frequency etc.), for a region exhibiting the strongest station trends in Australia, and compare these changes with minimum temperature extreme metrics derived from 10 GCMs, from the Coupled Model Inter-comparison Project Phase 5 (CMIP 5) datasets, and via statistical downscaling. We compare the observed trends with those derived from the "raw" GCM minimum temperature data as well as examine whether quantile matching (QM) or spatio-temporal (spTimerQM) modelling with Quantile Matching can be used to improve the correlation between observed and simulated extreme minimum temperatures. We demonstrate, that the spTimerQM modelling approach provides correlations with observed daily minimum temperatures for the period August to November of 0.22. This represents an almost fourfold improvement over either the "raw" GCM or QM results. The spTimerQM modelling approach also improves correlations with observed monthly frost frequency statistics to 0.84 as opposed to 0.37 and 0.81 for the "raw" GCM and QM results respectively. We apply the spatio-temporal model to examine future extreme minimum temperature projections for the period 2016 to 2048. The spTimerQM modelling results suggest the persistence of current levels of frost risk out to 2030, with the evidence of continuing decadal variation.

Estradiol and Antagonist Pretreatment Prior to Microdose Leuprolide in in Vitro Fertilization. Does It Improve IVF Outcomes in Poor Responders as Compared to Oral Contraceptive Pill?

Science.gov (United States)

Elassar, Alyaa; Nulsen, John; Engmann, Lawrence; Benadiva, Claudio

2015-01-01

To compare in vitro fertilization (IVF) outcomes in low responders stimulated with microdose leuprolide protocol (ML) following pretreatment with either oral contraceptive pill (OCP) or luteal estradiol (E2) + GnRH antagonist (E2 + antag) for follicular synchronization prior to controlled ovarian hyperstimulation (COH). This was a retrospective study of 130 women, who were poor responders, undergoing IVF with either OCP/ML or E2+ antag/ML protocols. The main outcome measures were ongoing pregnancy rates, number of oocytes retrieved, and cancellation rate. Both groups were similar in baseline characteristics. There were no significant differences in gonadotropin requirement, cancellation rate, and number of embryos transferred. Ongoing pregnancy rates (40% vs. 15%) were significantly higher in the OCP/ML group. Trends toward greater number of oocytes retrieved (7.7 ± 3.4 vs. 5.9 ± 4.2) and improved implantation rates (20% vs. 12%) were also noted, but these did not reach statistical significance. E2+antag pretreatment does not appear to improve IVF outcomes in ML protocol when compared to the standard OCP in poor responders. Randomized trials with adequate power to study the optimal method of steroid pretreatments appear justified.

The use of process models to inform and improve statistical models of nitrate occurrence, Great Miami River Basin, southwestern Ohio

Science.gov (United States)

Walter, Donald A.; Starn, J. Jeffrey

2013-01-01

local hydrologic settings, would inform and improve the development of statistical models can be implicitly estimated by evaluating the differences between explanatory variables estimated from the contributing recharge areas and the circular buffers used to develop existing statistical models. The larger the difference in estimated variables, the more likely that statistical models would be changed, and presumably improved, if explanatory variables estimated from contributing recharge areas were used in model development. Comparing model predictions from the two sets of estimated variables would further quantify—albeit implicitly—how an improved, physically based estimate of explanatory variables would be reflected in model predictions. Differences between the two sets of estimated explanatory variables and resultant model predictions vary spatially; greater differences are associated with areas of steep hydraulic gradients. A direct comparison, however, would require the development of a separate set of statistical models using explanatory variables from contributing recharge areas. Area-weighted means of three environmental variables—silt content, alfisol content, and depth to water from the U.S. Department of Agriculture State Soil Geographic (STATSGO) data—and one nitrogen-source variable (fertilizer-application rate from county data mapped to Enhanced National Land Cover Data 1992 (NLCDe 92) agricultural land use) can vary substantially between circular buffers and volume-equivalent contributing recharge areas and among contributing recharge areas for different sets of well variables. The differences in estimated explanatory variables are a function of the same factors affecting the contributing recharge areas as well as the spatial resolution and local distribution of the underlying spatial data. As a result, differences in estimated variables between circular buffers and contributing recharge areas are complex and site specific as evidenced by differences

Comparing the Effectiveness of Paroxetine, Attention Modification Program and Combination of both on Improving Social Anxiety Symptoms

Directory of Open Access Journals (Sweden)

Hosein Khedmatgozar

2012-08-01

Full Text Available Introduction: Although the effectiveness of paroxetine and Attention Modification Program has been studied separately in treating social anxiety disorder, there has been no research comparing them according to the literature. The aim of this study was to compare the effectiveness of paroxetine, Attention Modification Program (AMP and combination of both on improving the Social Anxiety Symptoms. Methods: 33 patients meeting DSM-IV-TR criteria for social anxiety disorder were randomly assigned in 3 groups: 11 in paroxetine group, 11 in AMP group and 11 in combined group. Treatment intervention was done during 8 weeks period. Social Phobia Inventory (SPIN, Beck Depression Inventory (BDI-II and Sheehan Disability Scale (SDS were administered before and after treatment intervention. One-way Analysis of Covariance (ANCOVA was used to determine the differences and efficacy of treatment interventions between groups. Data analysis was done by SPSS-16 software. Results: 28 participants completed the treatment period. One-way ANCOVA results showed statistically significant differences in post-treatment scores of social phobia (p=0/007, depressive symptoms (p=0.007 and daily life functioning (p=0.011 between three groups. Bonferroni correction showed that combined treatment is significantly more effective than AMP in reducing social phobia symptoms (p=0.007, depressive symptoms (p=0.022 and enhancing daily life functioning (0.019. Yet, there were no significant differences between Paroxetine and combined treatment in all post-treatment scores (p=0.890, p=1.000, p=1.000 for social phobia, depressive symptoms and daily life functioning respectively. Paroxetine showed more significant improvement of depressive symptoms (p=0.016 and enhancing daily life functioning (p=0.045 than AMP. Also, there were no significant differences between paroxetine and AMP in reducing social anxiety symptoms. Discussion: It seems that paroxetine has wider effect in reducing social

Comparing the Effectiveness of Paroxetine, Attention Modification Program and Combination of both on Improving Social Anxiety Symptoms

Directory of Open Access Journals (Sweden)

Aliasghar Asgharnejad Farid

2012-09-01

Full Text Available Introduction: Although the effectiveness of paroxetine and Attention Modification Program has been studied separately in treating social anxiety disorder, there has been no research comparing them according to the literature. The aim of this study was to compare the effectiveness of paroxetine, Attention Modification Program (AMP and combination of both on improving the Social Anxiety Symptoms.Methods:33 patients meeting DSM-IV-TR criteria for social anxiety disorder were randomly assigned in 3 groups: 11 in paroxetine group, 11 in AMP group and 11 in combined group. Treatment intervention was done during 8 weeks period. Social Phobia Inventory (SPIN, Beck Depression Inventory (BDI-II and Sheehan Disability Scale (SDS were administered before and after treatment intervention. One-way Analysis of Covariance (ANCOVA was used to determine the differences and efficacy of treatment interventions between groups. Data analysis was done by SPSS-16 software.Results:28 participants completed the treatment period. One-way ANCOVA results showed statistically significant differences in post-treatment scores of social phobia (p=0/007, depressive symptoms (p=0.007 and daily life functioning (p=0.011 between three groups. Bonferroni correction showed that combined treatment is significantly more effective than AMP in reducing social phobia symptoms (p=0.007, depressive symptoms (p=0.022 and enhancing daily life functioning (0.019. Yet, there were no significant differences between Paroxetine and combined treatment in all post-treatment scores (p=0.890, p=1.000, p=1.000 for social phobia, depressive symptoms and daily life functioning respectively. Paroxetine showed more significant improvement of depressive symptoms (p=0.016 and enhancing daily life functioning (p=0.045 than AMP. Also, there were no significant differences between paroxetine and AMP in reducing social anxiety symptoms.Discussion:It seems that paroxetine has wider effect in reducing social

Adaptive statistical iterative reconstruction improves image quality without affecting perfusion CT quantitation in primary colorectal cancer

Directory of Open Access Journals (Sweden)

D. Prezzi

Full Text Available Objectives: To determine the effect of Adaptive Statistical Iterative Reconstruction (ASIR on perfusion CT (pCT parameter quantitation and image quality in primary colorectal cancer. Methods: Prospective observational study. Following institutional review board approval and informed consent, 32 patients with colorectal adenocarcinoma underwent pCT (100 kV, 150 mA, 120 s acquisition, axial mode. Tumour regional blood flow (BF, blood volume (BV, mean transit time (MTT and permeability surface area product (PS were determined using identical regions-of-interests for ASIR percentages of 0%, 20%, 40%, 60%, 80% and 100%. Image noise, contrast-to-noise ratio (CNR and pCT parameters were assessed across ASIR percentages. Coefficients of variation (CV, repeated measures analysis of variance (rANOVA and Spearman’ rank order correlation were performed with statistical significance at 5%. Results: With increasing ASIR percentages, image noise decreased by 33% while CNR increased by 61%; peak tumour CNR was greater than 1.5 with 60% ASIR and above. Mean BF, BV, MTT and PS differed by less than 1.8%, 2.9%, 2.5% and 2.6% across ASIR percentages. CV were 4.9%, 4.2%, 3.3% and 7.9%; rANOVA P values: 0.85, 0.62, 0.02 and 0.81 respectively. Conclusions: ASIR improves image noise and CNR without altering pCT parameters substantially. Keywords: Perfusion imaging, Multidetector computed tomography, Colorectal neoplasms, Computer-assisted image processing, Radiation dosage

Understanding Statistics - Cancer Statistics

Science.gov (United States)

Annual reports of U.S. cancer statistics including new cases, deaths, trends, survival, prevalence, lifetime risk, and progress toward Healthy People targets, plus statistical summaries for a number of common cancer types.

Comparative statistical analysis of chrome and vegetable tanning effluents and their effects on related soil

International Nuclear Information System (INIS)

Tariq, Saadia R.; Shah, Munir H.; Shaheen, Nazia

2009-01-01

Two tanning units of Pakistan, namely, Kasur and Mian Channun were investigated with respect to the tanning processes (chrome and vegetable, respectively) and the effects of the tanning agents on the quality of soil in vicinity of tanneries were evaluated. The effluent and soil samples from 16 tanneries each of Kasur and Mian Channun were collected. The levels of selected metals (Na, K, Ca, Mg, Fe, Cr, Mn, Co, Cd, Ni, Pb and Zn) were determined by using flame atomic absorption spectrophotometer under optimum analytical conditions. The data thus obtained were subjected to univariate and multivariate statistical analyses. Most of the metals exhibited considerably higher concentrations in the effluents and soils of Kasur compared with those of Mian Channun. It was observed that the soil of Kasur was highly contaminated by Na, K, Ca and Mg emanating from various processes of leather manufacture. Furthermore, the levels of Cr were also present at much enhanced levels than its background concentration due to the adoption of chrome tanning. The levels of Cr determined in soil samples collected from the vicinity of Mian Channun tanneries were almost comparable to the background levels. The soil of this city was found to have contaminated only by the metals originating from pre-tanning processes. The apportionment of selected metals in the effluent and soil samples was determined by a multivariate cluster analysis, which revealed significant differences in chrome and vegetable tanning processes.

Comparative statistical analysis of chrome and vegetable tanning effluents and their effects on related soil.

Science.gov (United States)

Tariq, Saadia R; Shah, Munir H; Shaheen, Nazia

2009-09-30

Two tanning units of Pakistan, namely, Kasur and Mian Channun were investigated with respect to the tanning processes (chrome and vegetable, respectively) and the effects of the tanning agents on the quality of soil in vicinity of tanneries were evaluated. The effluent and soil samples from 16 tanneries each of Kasur and Mian Channun were collected. The levels of selected metals (Na, K, Ca, Mg, Fe, Cr, Mn, Co, Cd, Ni, Pb and Zn) were determined by using flame atomic absorption spectrophotometer under optimum analytical conditions. The data thus obtained were subjected to univariate and multivariate statistical analyses. Most of the metals exhibited considerably higher concentrations in the effluents and soils of Kasur compared with those of Mian Channun. It was observed that the soil of Kasur was highly contaminated by Na, K, Ca and Mg emanating from various processes of leather manufacture. Furthermore, the levels of Cr were also present at much enhanced levels than its background concentration due to the adoption of chrome tanning. The levels of Cr determined in soil samples collected from the vicinity of Mian Channun tanneries were almost comparable to the background levels. The soil of this city was found to have contaminated only by the metals originating from pre-tanning processes. The apportionment of selected metals in the effluent and soil samples was determined by a multivariate cluster analysis, which revealed significant differences in chrome and vegetable tanning processes.

Comparative statistical analysis of chrome and vegetable tanning effluents and their effects on related soil

Energy Technology Data Exchange (ETDEWEB)

Tariq, Saadia R. [Department of Chemistry, Lahore College for Women University, Lahore (Pakistan); Shah, Munir H., E-mail: munir_qau@yahoo.com [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shaheen, Nazia [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2009-09-30

Two tanning units of Pakistan, namely, Kasur and Mian Channun were investigated with respect to the tanning processes (chrome and vegetable, respectively) and the effects of the tanning agents on the quality of soil in vicinity of tanneries were evaluated. The effluent and soil samples from 16 tanneries each of Kasur and Mian Channun were collected. The levels of selected metals (Na, K, Ca, Mg, Fe, Cr, Mn, Co, Cd, Ni, Pb and Zn) were determined by using flame atomic absorption spectrophotometer under optimum analytical conditions. The data thus obtained were subjected to univariate and multivariate statistical analyses. Most of the metals exhibited considerably higher concentrations in the effluents and soils of Kasur compared with those of Mian Channun. It was observed that the soil of Kasur was highly contaminated by Na, K, Ca and Mg emanating from various processes of leather manufacture. Furthermore, the levels of Cr were also present at much enhanced levels than its background concentration due to the adoption of chrome tanning. The levels of Cr determined in soil samples collected from the vicinity of Mian Channun tanneries were almost comparable to the background levels. The soil of this city was found to have contaminated only by the metals originating from pre-tanning processes. The apportionment of selected metals in the effluent and soil samples was determined by a multivariate cluster analysis, which revealed significant differences in chrome and vegetable tanning processes.

Improvement of vertical velocity statistics measured by a Doppler lidar through comparison with sonic anemometer observations

Science.gov (United States)

Bonin, Timothy A.; Newman, Jennifer F.; Klein, Petra M.; Chilson, Phillip B.; Wharton, Sonia

2016-12-01

Since turbulence measurements from Doppler lidars are being increasingly used within wind energy and boundary-layer meteorology, it is important to assess and improve the accuracy of these observations. While turbulent quantities are measured by Doppler lidars in several different ways, the simplest and most frequently used statistic is vertical velocity variance (w'2) from zenith stares. However, the competing effects of signal noise and resolution volume limitations, which respectively increase and decrease w'2, reduce the accuracy of these measurements. Herein, an established method that utilises the autocovariance of the signal to remove noise is evaluated and its skill in correcting for volume-averaging effects in the calculation of w'2 is also assessed. Additionally, this autocovariance technique is further refined by defining the amount of lag time to use for the most accurate estimates of w'2. Through comparison of observations from two Doppler lidars and sonic anemometers on a 300 m tower, the autocovariance technique is shown to generally improve estimates of w'2. After the autocovariance technique is applied, values of w'2 from the Doppler lidars are generally in close agreement (R2 ≈ 0.95 - 0.98) with those calculated from sonic anemometer measurements.

Statistical Optics

Science.gov (United States)

Goodman, Joseph W.

2000-07-01

The Wiley Classics Library consists of selected books that have become recognized classics in their respective fields. With these new unabridged and inexpensive editions, Wiley hopes to extend the life of these important works by making them available to future generations of mathematicians and scientists. Currently available in the Series: T. W. Anderson The Statistical Analysis of Time Series T. S. Arthanari & Yadolah Dodge Mathematical Programming in Statistics Emil Artin Geometric Algebra Norman T. J. Bailey The Elements of Stochastic Processes with Applications to the Natural Sciences Robert G. Bartle The Elements of Integration and Lebesgue Measure George E. P. Box & Norman R. Draper Evolutionary Operation: A Statistical Method for Process Improvement George E. P. Box & George C. Tiao Bayesian Inference in Statistical Analysis R. W. Carter Finite Groups of Lie Type: Conjugacy Classes and Complex Characters R. W. Carter Simple Groups of Lie Type William G. Cochran & Gertrude M. Cox Experimental Designs, Second Edition Richard Courant Differential and Integral Calculus, Volume I RIchard Courant Differential and Integral Calculus, Volume II Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume I Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume II D. R. Cox Planning of Experiments Harold S. M. Coxeter Introduction to Geometry, Second Edition Charles W. Curtis & Irving Reiner Representation Theory of Finite Groups and Associative Algebras Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume I Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume II Cuthbert Daniel Fitting Equations to Data: Computer Analysis of Multifactor Data, Second Edition Bruno de Finetti Theory of Probability, Volume I Bruno de Finetti Theory of Probability, Volume 2 W. Edwards Deming Sample Design in Business Research

Using statistical process control for monitoring the prevalence of hospital-acquired pressure ulcers.

Science.gov (United States)

Kottner, Jan; Halfens, Ruud

2010-05-01

Institutionally acquired pressure ulcers are used as outcome indicators to assess the quality of pressure ulcer prevention programs. Determining whether quality improvement projects that aim to decrease the proportions of institutionally acquired pressure ulcers lead to real changes in clinical practice depends on the measurement method and statistical analysis used. To examine whether nosocomial pressure ulcer prevalence rates in hospitals in the Netherlands changed, a secondary data analysis using different statistical approaches was conducted of annual (1998-2008) nationwide nursing-sensitive health problem prevalence studies in the Netherlands. Institutions that participated regularly in all survey years were identified. Risk-adjusted nosocomial pressure ulcers prevalence rates, grade 2 to 4 (European Pressure Ulcer Advisory Panel system) were calculated per year and hospital. Descriptive statistics, chi-square trend tests, and P charts based on statistical process control (SPC) were applied and compared. Six of the 905 healthcare institutions participated in every survey year and 11,444 patients in these six hospitals were identified as being at risk for pressure ulcers. Prevalence rates per year ranged from 0.05 to 0.22. Chi-square trend tests revealed statistically significant downward trends in four hospitals but based on SPC methods, prevalence rates of five hospitals varied by chance only. Results of chi-square trend tests and SPC methods were not comparable, making it impossible to decide which approach is more appropriate. P charts provide more valuable information than single P values and are more helpful for monitoring institutional performance. Empirical evidence about the decrease of nosocomial pressure ulcer prevalence rates in the Netherlands is contradictory and limited.

A goodness of fit statistic for the geometric distribution

NARCIS (Netherlands)

J.A. Ferreira

2003-01-01

textabstractWe propose a goodness of fit statistic for the geometric distribution and compare it in terms of power, via simulation, with the chi-square statistic. The statistic is based on the Lau-Rao theorem and can be seen as a discrete analogue of the total time on test statistic. The results

High impact  =  high statistical standards? Not necessarily so.

Science.gov (United States)

Tressoldi, Patrizio E; Giofré, David; Sella, Francesco; Cumming, Geoff

2013-01-01

What are the statistical practices of articles published in journals with a high impact factor? Are there differences compared with articles published in journals with a somewhat lower impact factor that have adopted editorial policies to reduce the impact of limitations of Null Hypothesis Significance Testing? To investigate these questions, the current study analyzed all articles related to psychological, neuropsychological and medical issues, published in 2011 in four journals with high impact factors: Science, Nature, The New England Journal of Medicine and The Lancet, and three journals with relatively lower impact factors: Neuropsychology, Journal of Experimental Psychology-Applied and the American Journal of Public Health. Results show that Null Hypothesis Significance Testing without any use of confidence intervals, effect size, prospective power and model estimation, is the prevalent statistical practice used in articles published in Nature, 89%, followed by articles published in Science, 42%. By contrast, in all other journals, both with high and lower impact factors, most articles report confidence intervals and/or effect size measures. We interpreted these differences as consequences of the editorial policies adopted by the journal editors, which are probably the most effective means to improve the statistical practices in journals with high or low impact factors.

High Impact = High Statistical Standards? Not Necessarily So

Science.gov (United States)

Tressoldi, Patrizio E.; Giofré, David; Sella, Francesco; Cumming, Geoff

2013-01-01

What are the statistical practices of articles published in journals with a high impact factor? Are there differences compared with articles published in journals with a somewhat lower impact factor that have adopted editorial policies to reduce the impact of limitations of Null Hypothesis Significance Testing? To investigate these questions, the current study analyzed all articles related to psychological, neuropsychological and medical issues, published in 2011 in four journals with high impact factors: Science, Nature, The New England Journal of Medicine and The Lancet, and three journals with relatively lower impact factors: Neuropsychology, Journal of Experimental Psychology-Applied and the American Journal of Public Health. Results show that Null Hypothesis Significance Testing without any use of confidence intervals, effect size, prospective power and model estimation, is the prevalent statistical practice used in articles published in Nature, 89%, followed by articles published in Science, 42%. By contrast, in all other journals, both with high and lower impact factors, most articles report confidence intervals and/or effect size measures. We interpreted these differences as consequences of the editorial policies adopted by the journal editors, which are probably the most effective means to improve the statistical practices in journals with high or low impact factors. PMID:23418533

Comparing Kaolin and Pinolene to Improve Sustainable Grapevine Production during Drought

OpenAIRE

Brillante, Luca; Belfiore, Nicola; Gaiotti, Federica; Lovat, Lorenzo; Sansone, Luigi; Poni, Stefano; Tomasi, Diego

2016-01-01

Viticulture is widely practiced in dry regions, where the grapevine is greatly exposed to water stress. Optimizing plant water use efficiency (WUE) without affecting crop yield, grape and wine quality is crucial to limiting use of water for irrigation and to significantly improving viticulture sustainability. This study examines the use in vineyards of particle film technology (engineered kaolin) and compares it to a film-forming antitranspirant (pinolene), traditionally used to limit leaf wa...

Comparing safety climate in naval aviation and hospitals: implications for improving patient safety.

Science.gov (United States)

Singer, Sara J; Rosen, Amy; Zhao, Shibei; Ciavarelli, Anthony P; Gaba, David M

2010-01-01

Evidence of variation in safety climate suggests the need for improvement among at least some hospitals. However, comparisons only among hospitals may underestimate the improvement required. Comparison of hospitals with analogous industries may provide a broader perspective on the safety status of our nation's hospitals. The purpose of this study was to compare safety climate among hospital workers with personnel from naval aviation, an organization that operates with high reliability despite intrinsically hazardous conditions. We surveyed a random sample of health care workers in 67 U.S. hospitals and, for generalizability, 30 veterans affairs hospitals using questions comparable with those posed at approximately the same time (2007) to a census of personnel from 35 squadrons of U.S. naval aviators. We received 13,841 (41%) completed surveys in U.S. hospitals, 5,511 (50%) in veterans affairs hospitals, and 14,854 (82%) among naval aviators. We examined differences in respondents' perceptions of safety climate at their institution overall and for 16 individual items. Safety climate was three times better on average among naval aviators than among hospital personnel. Naval aviators perceived a safer climate (up to seven times safer) than hospital personnel with respect to each of the 16 survey items. Compared with hospital managers, naval commanders perceived climate more like frontline personnel did. When contrasting naval aviators with hospital personnel working in comparably hazardous areas, safety climate discrepancies increased rather than decreased. One individual hospital performed as well as naval aviation on average, and at least one hospital outperformed the Navy benchmark for all but three individual survey items. Results suggest that hospitals have not sufficiently created a uniform priority of safety. However, if each hospital performed as well as the top-performing hospital in each area measured, hospitals could achieve safety climate levels comparable

Statistical techniques to extract information during SMAP soil moisture assimilation

Science.gov (United States)

Kolassa, J.; Reichle, R. H.; Liu, Q.; Alemohammad, S. H.; Gentine, P.

2017-12-01

Statistical techniques permit the retrieval of soil moisture estimates in a model climatology while retaining the spatial and temporal signatures of the satellite observations. As a consequence, the need for bias correction prior to an assimilation of these estimates is reduced, which could result in a more effective use of the independent information provided by the satellite observations. In this study, a statistical neural network (NN) retrieval algorithm is calibrated using SMAP brightness temperature observations and modeled soil moisture estimates (similar to those used to calibrate the SMAP Level 4 DA system). Daily values of surface soil moisture are estimated using the NN and then assimilated into the NASA Catchment model. The skill of the assimilation estimates is assessed based on a comprehensive comparison to in situ measurements from the SMAP core and sparse network sites as well as the International Soil Moisture Network. The NN retrieval assimilation is found to significantly improve the model skill, particularly in areas where the model does not represent processes related to agricultural practices. Additionally, the NN method is compared to assimilation experiments using traditional bias correction techniques. The NN retrieval assimilation is found to more effectively use the independent information provided by SMAP resulting in larger model skill improvements than assimilation experiments using traditional bias correction techniques.

Does prolonged β-lactam infusions improve clinical outcomes compared to intermittent infusions? A meta-analysis and systematic review of randomized, controlled trials

Directory of Open Access Journals (Sweden)

Van Arendonk Kyle J

2011-06-01

Full Text Available Abstract Background The emergence of multi-drug resistant Gram-negatives (MDRGNs coupled with an alarming scarcity of new antibiotics has forced the optimization of the therapeutic potential of available antibiotics. To exploit the time above the minimum inhibitory concentration mechanism of β-lactams, prolonging their infusion may improve outcomes. The primary objective of this meta-analysis was to determine if prolonged β-lactam infusion resulted in decreased mortality and improved clinical cure compared to intermittent β-lactam infusion. Methods Relevant studies were identified from searches of MEDLINE, EMBASE, and CENTRAL. Heterogeneity was assessed qualitatively, in addition to I2 and Chi-square statistics. Pooled relative risks (RR and 95% confidence intervals (CI were calculated using Mantel-Haenszel random-effects models. Results Fourteen randomized controlled trials (RCTs were included. Prolonged infusion β-lactams were not associated with decreased mortality (n= 982; RR 0.92; 95% CI:0.61-1.37 or clinical cure (n = 1380; RR 1.00 95% CI:0.94-1.06 compared to intermittent infusions. Subgroup analysis for β-lactam subclasses and equivalent total daily β-lactam doses yielded similar results. Most studies had notable methodological flaws. Conclusions No clinical advantage was observed for prolonged infusion β-lactams. The limited number of studies with MDRGNs precluded evaluation of prolonged infusion of β-lactams for this subgroup. A large, multicenter RCT with critically ill patients infected with MDRGNs is needed.

SU-C-BRD-01: A Statistical Modeling Method for Quality Control of Intensity- Modulated Radiation Therapy Planning

International Nuclear Information System (INIS)

Gao, S; Meyer, R; Shi, L; D'Souza, W; Zhang, H

2014-01-01

Purpose: To apply a statistical modeling approach, threshold modeling (TM), for quality control of intensity-modulated radiation therapy (IMRT) treatment plans. Methods: A quantitative measure, which was the weighted sum of violations of dose/dose-volume constraints, was first developed to represent the quality of each IMRT plan. Threshold modeling approach, which is is an extension of extreme value theory in statistics and is an effect way to model extreme values, was then applied to analyze the quality of the plans summarized by our quantitative measures. Our approach modeled the plans generated by planners as a series of independent and identically distributed random variables and described the behaviors of them if the plan quality was controlled below certain threshold. We tested our approach with five locally advanced head and neck cancer patients retrospectively. Two statistics were incorporated for numerical analysis: probability of quality improvement (PQI) of the plans and expected amount of improvement on the quantitative measure (EQI). Results: After clinical planners generated 15 plans for each patient, we applied our approach to obtain the PQI and EQI as if planners would generate additional 15 plans. For two of the patients, the PQI was significantly higher than the other three (0.17 and 0.18 comparing to 0.08, 0.01 and 0.01). The actual percentage of the additional 15 plans that outperformed the best of initial 15 plans was 20% and 27% comparing to 11%, 0% and 0%. EQI for the two potential patients were 34.5 and 32.9 and the rest of three patients were 9.9, 1.4 and 6.6. The actual improvements obtained were 28.3 and 20.5 comparing to 6.2, 0 and 0. Conclusion: TM is capable of reliably identifying the potential quality improvement of IMRT plans. It provides clinicians an effective tool to assess the trade-off between extra planning effort and achievable plan quality. This work was supported in part by NIH/NCI grant CA130814

Statistical process control in wine industry using control cards

OpenAIRE

Dimitrieva, Evica; Atanasova-Pacemska, Tatjana; Pacemska, Sanja

2013-01-01

This paper is based on the research of the technological process of automatic filling of bottles of wine in winery in Stip, Republic of Macedonia. The statistical process control using statistical control card is created. The results and recommendations for improving the process are discussed.

Kolmogorov-Smirnov statistical test for analysis of ZAP-70 expression in B-CLL, compared with quantitative PCR and IgV(H) mutation status.

Science.gov (United States)

Van Bockstaele, Femke; Janssens, Ann; Piette, Anne; Callewaert, Filip; Pede, Valerie; Offner, Fritz; Verhasselt, Bruno; Philippé, Jan

2006-07-15

ZAP-70 has been proposed as a surrogate marker for immunoglobulin heavy-chain variable region (IgV(H)) mutation status, which is known as a prognostic marker in B-cell chronic lymphocytic leukemia (CLL). The flow cytometric analysis of ZAP-70 suffers from difficulties in standardization and interpretation. We applied the Kolmogorov-Smirnov (KS) statistical test to make analysis more straightforward. We examined ZAP-70 expression by flow cytometry in 53 patients with CLL. Analysis was performed as initially described by Crespo et al. (New England J Med 2003; 348:1764-1775) and alternatively by application of the KS statistical test comparing T cells with B cells. Receiver-operating-characteristics (ROC)-curve analyses were performed to determine the optimal cut-off values for ZAP-70 measured by the two approaches. ZAP-70 protein expression was compared with ZAP-70 mRNA expression measured by a quantitative PCR (qPCR) and with the IgV(H) mutation status. Both flow cytometric analyses correlated well with the molecular technique and proved to be of equal value in predicting the IgV(H) mutation status. Applying the KS test is reproducible, simple, straightforward, and overcomes a number of difficulties encountered in the Crespo-method. The KS statistical test is an essential part of the software delivered with modern routine analytical flow cytometers and is well suited for analysis of ZAP-70 expression in CLL. (c) 2006 International Society for Analytical Cytology.

MetaComp: comprehensive analysis software for comparative meta-omics including comparative metagenomics.

Science.gov (United States)

Zhai, Peng; Yang, Longshu; Guo, Xiao; Wang, Zhe; Guo, Jiangtao; Wang, Xiaoqi; Zhu, Huaiqiu

2017-10-02

During the past decade, the development of high throughput nucleic sequencing and mass spectrometry analysis techniques have enabled the characterization of microbial communities through metagenomics, metatranscriptomics, metaproteomics and metabolomics data. To reveal the diversity of microbial communities and interactions between living conditions and microbes, it is necessary to introduce comparative analysis based upon integration of all four types of data mentioned above. Comparative meta-omics, especially comparative metageomics, has been established as a routine process to highlight the significant differences in taxon composition and functional gene abundance among microbiota samples. Meanwhile, biologists are increasingly concerning about the correlations between meta-omics features and environmental factors, which may further decipher the adaptation strategy of a microbial community. We developed a graphical comprehensive analysis software named MetaComp comprising a series of statistical analysis approaches with visualized results for metagenomics and other meta-omics data comparison. This software is capable to read files generated by a variety of upstream programs. After data loading, analyses such as multivariate statistics, hypothesis testing of two-sample, multi-sample as well as two-group sample and a novel function-regression analysis of environmental factors are offered. Here, regression analysis regards meta-omic features as independent variable and environmental factors as dependent variables. Moreover, MetaComp is capable to automatically choose an appropriate two-group sample test based upon the traits of input abundance profiles. We further evaluate the performance of its choice, and exhibit applications for metagenomics, metaproteomics and metabolomics samples. MetaComp, an integrative software capable for applying to all meta-omics data, originally distills the influence of living environment on microbial community by regression analysis

Statistical framework for decision making in mine action

DEFF Research Database (Denmark)

2007-01-01

The lecture discusses the basics of statistical decision making in connection with humanitarian mine action. There is special focus on: 1) requirements for mine detection; 2) design and evaluation and confidence of mine equipment; 3) efficient mine action by hierarchical approaches; 4) performance...... improvement by statistical learning and information fusion; 5) the advantage of using combined methods....

Principal Components of Superhigh-Dimensional Statistical Features and Support Vector Machine for Improving Identification Accuracies of Different Gear Crack Levels under Different Working Conditions

Directory of Open Access Journals (Sweden)

Dong Wang

2015-01-01

Full Text Available Gears are widely used in gearbox to transmit power from one shaft to another. Gear crack is one of the most frequent gear fault modes found in industry. Identification of different gear crack levels is beneficial in preventing any unexpected machine breakdown and reducing economic loss because gear crack leads to gear tooth breakage. In this paper, an intelligent fault diagnosis method for identification of different gear crack levels under different working conditions is proposed. First, superhigh-dimensional statistical features are extracted from continuous wavelet transform at different scales. The number of the statistical features extracted by using the proposed method is 920 so that the extracted statistical features are superhigh dimensional. To reduce the dimensionality of the extracted statistical features and generate new significant low-dimensional statistical features, a simple and effective method called principal component analysis is used. To further improve identification accuracies of different gear crack levels under different working conditions, support vector machine is employed. Three experiments are investigated to show the superiority of the proposed method. Comparisons with other existing gear crack level identification methods are conducted. The results show that the proposed method has the highest identification accuracies among all existing methods.

Improving the Document Development Process: Integrating Relational Data and Statistical Process Control.

Science.gov (United States)

Miller, John

1994-01-01

Presents an approach to document numbering, document titling, and process measurement which, when used with fundamental techniques of statistical process control, reveals meaningful process-element variation as well as nominal productivity models. (SR)

Comparative Estimation of Russia’s Regions Investment Potential on the Base of the Multivariate Statistical Analysis

Directory of Open Access Journals (Sweden)

Victor V. Nikitin

2013-01-01

Full Text Available The article introduces the algorithm of Russia’s regions investment potential estimation, developed by means of multivariate statistical methods, determines the factors, reflecting regions investment state. The integral indicator was developed on their basis, using statistical data. The article presents regions’ classification on the basis of the integral index

Research design and statistical methods in Indian medical journals: a retrospective survey.

Science.gov (United States)

Hassan, Shabbeer; Yellur, Rajashree; Subramani, Pooventhan; Adiga, Poornima; Gokhale, Manoj; Iyer, Manasa S; Mayya, Shreemathi S

2015-01-01

Good quality medical research generally requires not only an expertise in the chosen medical field of interest but also a sound knowledge of statistical methodology. The number of medical research articles which have been published in Indian medical journals has increased quite substantially in the past decade. The aim of this study was to collate all evidence on study design quality and statistical analyses used in selected leading Indian medical journals. Ten (10) leading Indian medical journals were selected based on impact factors and all original research articles published in 2003 (N = 588) and 2013 (N = 774) were categorized and reviewed. A validated checklist on study design, statistical analyses, results presentation, and interpretation was used for review and evaluation of the articles. Main outcomes considered in the present study were - study design types and their frequencies, error/defects proportion in study design, statistical analyses, and implementation of CONSORT checklist in RCT (randomized clinical trials). From 2003 to 2013: The proportion of erroneous statistical analyses did not decrease (χ2=0.592, Φ=0.027, p=0.4418), 25% (80/320) in 2003 compared to 22.6% (111/490) in 2013. Compared with 2003, significant improvement was seen in 2013; the proportion of papers using statistical tests increased significantly (χ2=26.96, Φ=0.16, pdesign decreased significantly (χ2=16.783, Φ=0.12 pdesigns has remained very low (7.3%, 43/588) with majority showing some errors (41 papers, 95.3%). Majority of the published studies were retrospective in nature both in 2003 [79.1% (465/588)] and in 2013 [78.2% (605/774)]. Major decreases in error proportions were observed in both results presentation (χ2=24.477, Φ=0.17, presearch seems to have made no major progress regarding using correct statistical analyses, but error/defects in study designs have decreased significantly. Randomized clinical trials are quite rarely published and have high proportion of

[Cause-of-death statistics and ICD, quo vadis?

Science.gov (United States)

Eckert, Olaf; Vogel, Ulrich

2018-07-01

The International Statistical Classification of Diseases and Related Health Problems (ICD) is the worldwide binding standard for generating underlying cause-of-death statistics. What are the effects of former revisions of the ICD on underlying cause-of-death statistics and which opportunities and challenges are becoming apparent in a possible transition process from ICD-10 to ICD-11?This article presents the calculation of the exploitation grade of ICD-9 and ICD-10 in the German cause-of-death statistics and quality of documentation. Approximately 67,000 anonymized German death certificates are processed by Iris/MUSE and official German cause-of-death statistics are analyzed.In addition to substantial changes in the exploitation grade in the transition from ICD-9 to ICD-10, regional effects become visible. The rate of so-called "ill-defined" conditions exceeds 10%.Despite substantial improvement of ICD revisions there are long-known deficits in the coroner's inquest, filling death certificates and quality of coding. To make better use of the ICD as a methodological framework for mortality statistics and health reporting in Germany, the following measures are necessary: 1. General use of Iris/MUSE, 2. Establishing multiple underlying cause-of-death statistics, 3. Introduction of an electronic death certificate, 4. Improvement of the medical assessment of cause of death.Within short time the WHO will release the 11th revision of the ICD that will provide additional opportunities for the development of underlying cause-of-death statistics and their use in science, public health and politics. A coordinated effort including participants in the process and users is necessary to meet the related challenges.

Nuts Improve Diet Quality Compared to Other Energy-Dense Snacks While Maintaining Body Weight

Directory of Open Access Journals (Sweden)

Siew Ling Tey

2011-01-01

Full Text Available Previous studies have reported that regular nut consumption reduces cardiovascular disease (CVD risk and does not promote weight gain despite the fact that nuts are energy-dense. However, no studies have investigated the body composition of those regularly consuming nuts compared to similar intakes of other snacks of equal energy density. This parallel study (n = 118 examined the effects of providing daily portions (~1100 kJ/d of hazelnuts, chocolate, or potato crisps compared to a control group receiving no snacks for twelve weeks. Effects on body weight and composition, blood lipids and lipoproteins, resting metabolic rate (RMR, appetite indices, and dietary quality were compared. At week 12, there was no significant difference in any of the outcome measurements between the groups except for dietary quality, which improved significantly in the nut group. Nuts can be incorporated into the diet without adversely affecting body weight and can improve diet quality.

A comparative study on methods of improving SCR for ship detection in SAR image

Science.gov (United States)

Lang, Haitao; Shi, Hongji; Tao, Yunhong; Ma, Li

2017-10-01

Knowledge about ship positions plays a critical role in a wide range of maritime applications. To improve the performance of ship detector in SAR image, an effective strategy is improving the signal-to-clutter ratio (SCR) before conducting detection. In this paper, we present a comparative study on methods of improving SCR, including power-law scaling (PLS), max-mean and max-median filter (MMF1 and MMF2), method of wavelet transform (TWT), traditional SPAN detector, reflection symmetric metric (RSM), scattering mechanism metric (SMM). The ability of SCR improvement to SAR image and ship detection performance associated with cell- averaging CFAR (CA-CFAR) of different methods are evaluated on two real SAR data.

Statistical Engine Knock Control

DEFF Research Database (Denmark)

Stotsky, Alexander A.

2008-01-01

A new statistical concept of the knock control of a spark ignition automotive engine is proposed . The control aim is associated with the statistical hy pothesis test which compares the threshold value to the average value of the max imal amplitud e of the knock sensor signal at a given freq uency....... C ontrol algorithm which is used for minimization of the regulation error realizes a simple count-up-count-d own logic. A new ad aptation algorithm for the knock d etection threshold is also d eveloped . C onfi d ence interval method is used as the b asis for ad aptation. A simple statistical mod el...... which includ es generation of the amplitud e signals, a threshold value d etermination and a knock sound mod el is d eveloped for evaluation of the control concept....

Finite-sample instrumental variables Inference using an Asymptotically Pivotal Statistic

NARCIS (Netherlands)

Bekker, P.; Kleibergen, F.R.

2001-01-01

The paper considers the K-statistic, Kleibergen’s (2000) adaptation ofthe Anderson-Rubin (AR) statistic in instrumental variables regression.Compared to the AR-statistic this K-statistic shows improvedasymptotic efficiency in terms of degrees of freedom in overidentifiedmodels and yet it shares,

Experimental statistics

CERN Document Server

Natrella, Mary Gibbons

1963-01-01

Formulated to assist scientists and engineers engaged in army ordnance research and development programs, this well-known and highly regarded handbook is a ready reference for advanced undergraduate and graduate students as well as for professionals seeking engineering information and quantitative data for designing, developing, constructing, and testing equipment. Topics include characterizing and comparing the measured performance of a material, product, or process; general considerations in planning experiments; statistical techniques for analyzing extreme-value data; use of transformations

A goodness of fit statistic for the geometric distribution

OpenAIRE

Ferreira, J.A.

2003-01-01

textabstractWe propose a goodness of fit statistic for the geometric distribution and compare it in terms of power, via simulation, with the chi-square statistic. The statistic is based on the Lau-Rao theorem and can be seen as a discrete analogue of the total time on test statistic. The results suggest that the test based on the new statistic is generally superior to the chi-square test.

Comparing simulated and theoretical sampling distributions of the U3 person-fit statistic

NARCIS (Netherlands)

Emons, W.H.M.; Meijer, R.R.; Sijtsma, K.

2002-01-01

The accuracy with which the theoretical sampling distribution of van der Flier's person-.t statistic U3 approaches the empirical U3 sampling distribution is affected by the item discrimination. A simulation study showed that for tests with a moderate or a strong mean item discrimination, the Type I

Statistical Method to Overcome Overfitting Issue in Rational Function Models

Science.gov (United States)

Alizadeh Moghaddam, S. H.; Mokhtarzade, M.; Alizadeh Naeini, A.; Alizadeh Moghaddam, S. A.

2017-09-01

Rational function models (RFMs) are known as one of the most appealing models which are extensively applied in geometric correction of satellite images and map production. Overfitting is a common issue, in the case of terrain dependent RFMs, that degrades the accuracy of RFMs-derived geospatial products. This issue, resulting from the high number of RFMs' parameters, leads to ill-posedness of the RFMs. To tackle this problem, in this study, a fast and robust statistical approach is proposed and compared to Tikhonov regularization (TR) method, as a frequently-used solution to RFMs' overfitting. In the proposed method, a statistical test, namely, significance test is applied to search for the RFMs' parameters that are resistant against overfitting issue. The performance of the proposed method was evaluated for two real data sets of Cartosat-1 satellite images. The obtained results demonstrate the efficiency of the proposed method in term of the achievable level of accuracy. This technique, indeed, shows an improvement of 50-80% over the TR.

National Statistical Commission and Indian Official Statistics*

Indian Academy of Sciences (India)

IAS Admin

a good collection of official statistics of that time. With more .... statistical agencies and institutions to provide details of statistical activities .... ing several training programmes. .... ful completion of Indian Statistical Service examinations, the.

Statistical process control in nursing research.

Science.gov (United States)

Polit, Denise F; Chaboyer, Wendy

2012-02-01

In intervention studies in which randomization to groups is not possible, researchers typically use quasi-experimental designs. Time series designs are strong quasi-experimental designs but are seldom used, perhaps because of technical and analytic hurdles. Statistical process control (SPC) is an alternative analytic approach to testing hypotheses about intervention effects using data collected over time. SPC, like traditional statistical methods, is a tool for understanding variation and involves the construction of control charts that distinguish between normal, random fluctuations (common cause variation), and statistically significant special cause variation that can result from an innovation. The purpose of this article is to provide an overview of SPC and to illustrate its use in a study of a nursing practice improvement intervention. Copyright © 2011 Wiley Periodicals, Inc.

Comparing simulated and theoretical sampling distributions of the U3 person-fit statistic

NARCIS (Netherlands)

Emons, Wilco H.M.; Meijer, R.R.; Sijtsma, Klaas

2002-01-01

The accuracy with which the theoretical sampling distribution of van der Flier’s person-fit statistic U3 approaches the empirical U3 sampling distribution is affected by the item discrimination. A simulation study showed that for tests with a moderate or a strong mean item discrimination, the Type I

Applicability of statistical process control techniques

NARCIS (Netherlands)

Schippers, W.A.J.

1998-01-01

This paper concerns the application of Process Control Techniques (PCTs) for the improvement of the technical performance of discrete production processes. Successful applications of these techniques, such as Statistical Process Control Techniques (SPC), can be found in the literature. However, some

Teaching statistics to nursing students: an expert panel consensus.

Science.gov (United States)

Hayat, Matthew J; Eckardt, Patricia; Higgins, Melinda; Kim, MyoungJin; Schmiege, Sarah J

2013-06-01

Statistics education is a necessary element of nursing education, and its inclusion is recommended in the American Association of Colleges of Nursing guidelines for nurse training at all levels. This article presents a cohesive summary of an expert panel discussion, "Teaching Statistics to Nursing Students," held at the 2012 Joint Statistical Meetings. All panelists were statistics experts, had extensive teaching and consulting experience, and held faculty appointments in a U.S.-based nursing college or school. The panel discussed degree-specific curriculum requirements, course content, how to ensure nursing students understand the relevance of statistics, approaches to integrating statistics consulting knowledge, experience with classroom instruction, use of knowledge from the statistics education research field to make improvements in statistics education for nursing students, and classroom pedagogy and instruction on the use of statistical software. Panelists also discussed the need for evidence to make data-informed decisions about statistics education and training for nurses. Copyright 2013, SLACK Incorporated.

A case study: application of statistical process control tool for determining process capability and sigma level.

Science.gov (United States)

Chopra, Vikram; Bairagi, Mukesh; Trivedi, P; Nagar, Mona

2012-01-01

process control study on process. Interpretation of such a study provides information about stability, process variability, changing of trends, and quantification of process ability against defective production. Comparative evaluation of critical quality attributes by Pareto charts provides the least capable and most variable process that is liable for improvement. Statistical process control thus proves to be an important tool for six sigma-capable process development and continuous quality improvement.

Does cryotherapy improve skin circulation compared with compression and elevation in preventing venous leg ulcers?

Science.gov (United States)

Kelechi, Teresa J; Mueller, Martina; Madisetti, Mohan; Prentice, Margie A; Dooley, Mary J

2017-08-01

This trial compared skin blood flow, temperature and incidence of venous leg ulcers in patients with chronic venous disease using compression wraps and elevation pillows. Patients with CEAP C4 skin damage and C5 history of ulcers were randomly assigned to a cryotherapy intervention (n = 138) or placebo cuff control (n = 138) applied to the lower legs over 9 months. The time the ulcers healed prior to enrollment in the study for the cryotherapy group ranged from 1 to 2218 days (n = 8, median = 32 days); for the control group, the range was 24 to 489 days (n = 6, median = 390 days). There were no statistically significant blood flow changes measured in perfusion units with a laser Doppler flowmetre within or between the groups; mean difference between the groups was 0·62, P = 0·619. No differences were noted in skin temperature measured with an infrared thermometer within and between the groups; mean difference between the groups was -0·17°C, P = 0·540. Cryotherapy did not improve skin blood flow or temperature and did not show efficacy in preventing ulcers. However, at least 30% of intervention and 50% of control participants were anticipated to develop an ulcer during the study; only ∼7% occurred. These findings suggest that strict adherence to standard of care decreases the incidence of leg ulcers and remains a best practice for leg ulcer prevention. © 2016 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Working with numbers and statistics a handbook for journalists

CERN Document Server

Livingston, Charles

2005-01-01

Working With Numbers and Statistics: A Handbook for Journalists will bolster math skills and improve math confidence for journalists at all skill levels. Authors Charles Livingston and Paul Voakes developed this resource book to improve journalist

ArraySolver: an algorithm for colour-coded graphical display and Wilcoxon signed-rank statistics for comparing microarray gene expression data.

Science.gov (United States)

Khan, Haseeb Ahmad

2004-01-01

The massive surge in the production of microarray data poses a great challenge for proper analysis and interpretation. In recent years numerous computational tools have been developed to extract meaningful interpretation of microarray gene expression data. However, a convenient tool for two-groups comparison of microarray data is still lacking and users have to rely on commercial statistical packages that might be costly and require special skills, in addition to extra time and effort for transferring data from one platform to other. Various statistical methods, including the t-test, analysis of variance, Pearson test and Mann-Whitney U test, have been reported for comparing microarray data, whereas the utilization of the Wilcoxon signed-rank test, which is an appropriate test for two-groups comparison of gene expression data, has largely been neglected in microarray studies. The aim of this investigation was to build an integrated tool, ArraySolver, for colour-coded graphical display and comparison of gene expression data using the Wilcoxon signed-rank test. The results of software validation showed similar outputs with ArraySolver and SPSS for large datasets. Whereas the former program appeared to be more accurate for 25 or fewer pairs (n < or = 25), suggesting its potential application in analysing molecular signatures that usually contain small numbers of genes. The main advantages of ArraySolver are easy data selection, convenient report format, accurate statistics and the familiar Excel platform.

[The main directions of reforming the service of medical statistics in Ukraine].

Science.gov (United States)

Golubchykov, Mykhailo V; Orlova, Nataliia M; Bielikova, Inna V

2018-01-01

Introduction: Implementation of new methods of information support of managerial decision-making should ensure of the effective health system reform and create conditions for improving the quality of operational management, reasonable planning of medical care and increasing the efficiency of the use of system resources. Reforming of Medical Statistics Service of Ukraine should be considered only in the context of the reform of the entire health system. The aim: This work is an analysis of the current situation and justification of the main directions of reforming of Medical Statistics Service of Ukraine. Material and methods: In the work is used a range of methods: content analysis, bibliosemantic, systematic approach. The information base of the research became: WHO strategic and program documents, data of the Medical Statistics Center of the Ministry of Health of Ukraine. Review: The Medical Statistics Service of Ukraine has a completed and effective structure, headed by the State Institution "Medical Statistics Center of the Ministry of Health of Ukraine." This institution reports on behalf of the Ministry of Health of Ukraine to the State Statistical Service of Ukraine, the WHO European Office and other international organizations. An analysis of the current situation showed that to achieve this goal it is necessary: to improve the system of statistical indicators for an adequate assessment of the performance of health institutions, including in the economic aspect; creation of a developed medical and statistical base of administrative territories; change of existing technologies for the formation of information resources; strengthening the material-technical base of the structural units of Medical Statistics Service; improvement of the system of training and retraining of personnel for the service of medical statistics; development of international cooperation in the field of methodology and practice of medical statistics, implementation of internationally

Statistical literacy for clinical practitioners

CERN Document Server

Holmes, William H

2014-01-01

This textbook on statistics is written for students in medicine, epidemiology, and public health. It builds on the important role evidence-based medicine now plays in the clinical practice of physicians, physician assistants and allied health practitioners. By bringing research design and statistics to the fore, this book can integrate these skills into the curricula of professional programs. Students, particularly practitioners-in-training, will learn statistical skills that are required of today’s clinicians. Practice problems at the end of each chapter and downloadable data sets provided by the authors ensure readers get practical experience that they can then apply to their own work.  Topics covered include:   Functions of Statistics in Clinical Research Common Study Designs Describing Distributions of Categorical and Quantitative Variables Confidence Intervals and Hypothesis Testing Documenting Relationships in Categorical and Quantitative Data Assessing Screening and Diagnostic Tests Comparing Mean...

Statistical aspects of fish stock assessment

DEFF Research Database (Denmark)

Berg, Casper Willestofte

for stock assessment by application of state-of-the-art statistical methodology. The main contributions are presented in the form of six research papers. The major part of the thesis deals with age-structured assessment models, which is the most common approach. Conversion from length to age distributions...... statistical aspects of fish stocks assessment, which includes topics such as time series analysis, generalized additive models (GAMs), and non-linear state-space/mixed models capable of handling missing data and a high number of latent states and parameters. The aim is to improve the existing methods...

Peculiarities of Teaching Medical Informatics and Statistics

Directory of Open Access Journals (Sweden)

Sergey Glushkov

2017-05-01

Full Text Available The article reviews features of teaching Medical Informatics and Statistics. The course is referred to the disciplines of Mathematical and Natural sciences. The course is provided in all the faculties of I. M. Sechenov First Moscow State Medical University. For students of Preventive Medicine Department the time frame allotted for studying the course is significantly larger than for similar course provided at other faculties. To improve the teaching methodology of the discipline an analysis of the curriculum has been carried out, attendance and students’ performance statistics have been summarized. As a result, the main goals and objectives have been identified. Besides, general educational functions and the contribution to the solution of problems of education, students’ upbringing and development have been revealed; two stages of teaching have been presented. Recommendations referred to the newest methodological development aimed at improving the quality of teaching the discipline are provided. The ways of improving the methods and organizational forms of education are outlined.

Risk prediction model: Statistical and artificial neural network approach

Science.gov (United States)

Paiman, Nuur Azreen; Hariri, Azian; Masood, Ibrahim

2017-04-01

Prediction models are increasingly gaining popularity and had been used in numerous areas of studies to complement and fulfilled clinical reasoning and decision making nowadays. The adoption of such models assist physician's decision making, individual's behavior, and consequently improve individual outcomes and the cost-effectiveness of care. The objective of this paper is to reviewed articles related to risk prediction model in order to understand the suitable approach, development and the validation process of risk prediction model. A qualitative review of the aims, methods and significant main outcomes of the nineteen published articles that developed risk prediction models from numerous fields were done. This paper also reviewed on how researchers develop and validate the risk prediction models based on statistical and artificial neural network approach. From the review done, some methodological recommendation in developing and validating the prediction model were highlighted. According to studies that had been done, artificial neural network approached in developing the prediction model were more accurate compared to statistical approach. However currently, only limited published literature discussed on which approach is more accurate for risk prediction model development.

Statistics for clinical nursing practice: an introduction.

Science.gov (United States)

Rickard, Claire M

2008-11-01

Difficulty in understanding statistics is one of the most frequently reported barriers to nurses applying research results in their practice. Yet the amount of nursing research published each year continues to grow, as does the expectation that nurses will undertake practice based on this evidence. Critical care nurses do not need to be statisticians, but they do need to develop a working knowledge of statistics so they can be informed consumers of research and so practice can evolve and improve. For those undertaking a research project, statistical literacy is required to interact with other researchers and statisticians, so as to best design and undertake the project. This article is the first in a series that guides critical care nurses through statistical terms and concepts relevant to their practice.

Statistical learning methods: Basics, control and performance

Energy Technology Data Exchange (ETDEWEB)

Zimmermann, J. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Munich (Germany)]. E-mail: zimmerm@mppmu.mpg.de

2006-04-01

The basics of statistical learning are reviewed with a special emphasis on general principles and problems for all different types of learning methods. Different aspects of controlling these methods in a physically adequate way will be discussed. All principles and guidelines will be exercised on examples for statistical learning methods in high energy and astrophysics. These examples prove in addition that statistical learning methods very often lead to a remarkable performance gain compared to the competing classical algorithms.

Statistical learning methods: Basics, control and performance

International Nuclear Information System (INIS)

Zimmermann, J.

2006-01-01

The basics of statistical learning are reviewed with a special emphasis on general principles and problems for all different types of learning methods. Different aspects of controlling these methods in a physically adequate way will be discussed. All principles and guidelines will be exercised on examples for statistical learning methods in high energy and astrophysics. These examples prove in addition that statistical learning methods very often lead to a remarkable performance gain compared to the competing classical algorithms

Effect of the absolute statistic on gene-sampling gene-set analysis methods.

Science.gov (United States)

Nam, Dougu

2017-06-01

Gene-set enrichment analysis and its modified versions have commonly been used for identifying altered functions or pathways in disease from microarray data. In particular, the simple gene-sampling gene-set analysis methods have been heavily used for datasets with only a few sample replicates. The biggest problem with this approach is the highly inflated false-positive rate. In this paper, the effect of absolute gene statistic on gene-sampling gene-set analysis methods is systematically investigated. Thus far, the absolute gene statistic has merely been regarded as a supplementary method for capturing the bidirectional changes in each gene set. Here, it is shown that incorporating the absolute gene statistic in gene-sampling gene-set analysis substantially reduces the false-positive rate and improves the overall discriminatory ability. Its effect was investigated by power, false-positive rate, and receiver operating curve for a number of simulated and real datasets. The performances of gene-set analysis methods in one-tailed (genome-wide association study) and two-tailed (gene expression data) tests were also compared and discussed.

T2* Mapping Provides Information That Is Statistically Comparable to an Arthroscopic Evaluation of Acetabular Cartilage.

Science.gov (United States)

Morgan, Patrick; Nissi, Mikko J; Hughes, John; Mortazavi, Shabnam; Ellerman, Jutta

2017-07-01

Objectives The purpose of this study was to validate T2* mapping as an objective, noninvasive method for the prediction of acetabular cartilage damage. Methods This is the second step in the validation of T2*. In a previous study, we established a quantitative predictive model for identifying and grading acetabular cartilage damage. In this study, the model was applied to a second cohort of 27 consecutive hips to validate the model. A clinical 3.0-T imaging protocol with T2* mapping was used. Acetabular regions of interest (ROI) were identified on magnetic resonance and graded using the previously established model. Each ROI was then graded in a blinded fashion by arthroscopy. Accurate surgical location of ROIs was facilitated with a 2-dimensional map projection of the acetabulum. A total of 459 ROIs were studied. Results When T2* mapping and arthroscopic assessment were compared, 82% of ROIs were within 1 Beck group (of a total 6 possible) and 32% of ROIs were classified identically. Disease prediction based on receiver operating characteristic curve analysis demonstrated a sensitivity of 0.713 and a specificity of 0.804. Model stability evaluation required no significant changes to the predictive model produced in the initial study. Conclusions These results validate that T2* mapping provides statistically comparable information regarding acetabular cartilage when compared to arthroscopy. In contrast to arthroscopy, T2* mapping is quantitative, noninvasive, and can be used in follow-up. Unlike research quantitative magnetic resonance protocols, T2* takes little time and does not require a contrast agent. This may facilitate its use in the clinical sphere.

Chronic lung disease in very low birth weight infants: Persistence and improvement of a quality improvement process in a tertiary level neonatal intensive care unit.

Science.gov (United States)

Birenbaum, H J; Pfoh, E R; Helou, S; Pane, M A; Marinkovich, G A; Dentry, A; Yeh, Hsin-Chieh; Updegraff, L; Arnold, C; Liverman, S; Cawman, H

2016-05-19

We previously demonstrated a significant reduction in our incidence of chronic lung disease in our NICU using potentially better practices of avoiding delivery room endotracheal intubation and using early nasal CPAP. We sought to demonstrate whether these improvements were sustained and or improved over time. We conducted a retrospective, cross-sectional analysis of infants 501-1500 grams born at our hospital between 2005 and 2013. Infants born during the 2005-2007, 2008-2010 and 2011-2013 epochs were grouped together, respectively. Descriptive analysis was conducted to determine the number and percent of maternal and neonatal characteristics by year grouping. Chi-squared tests were used to determine whether there were any statistically significant changes in characteristics across year groupings.. Two outcome variables were assessed: a diagnosis of chronic lung disease based on the Vermont Oxford Network definition and being discharged home on supplemental oxygen. There was a statistically significant improvement in the incidence of chronic lung disease in infants below 27 weeks' gestation in the three year period in the 2011-2013 cohort compared with those in the 2005-2007 cohort. We also found a statistically significant improvement in the number of infants discharged on home oxygen with birth weights 751-1000 grams and infants with gestational age less than 27 weeks in the 2011-2013 cohort compared to the 2005-2007 cohort. We demonstrated sustained improvement in our incidence of CLD between 2005 and 2013. We speculate that a multifaceted strategy of avoiding intubation and excessive oxygen in the delivery room, the early use of CPAP, as well as the use of volume targeted ventilation, when needed, may help significantly reduce the incidence of CLD.

Long-term energy efficiency analysis requires solid energy statistics: The case of the German basic chemical industry

International Nuclear Information System (INIS)

Saygin, D.; Worrell, E.; Tam, C.; Trudeau, N.; Gielen, D.J.; Weiss, M.; Patel, M.K.

2012-01-01

Analyzing the chemical industry’s energy use is challenging because of the sector’s complexity and the prevailing uncertainty in energy use and production data. We develop an advanced bottom-up model (PIE-Plus) which encompasses the energy use of the 139 most important chemical processes. We apply this model in a case study to analyze the German basic chemical industry’s energy use and energy efficiency improvements in the period between 1995 and 2008. We compare our results with data from the German Energy Balances and with data published by the International Energy Agency (IEA). We find that our model covers 88% of the basic chemical industry’s total final energy use (including non-energy use) as reported in the German Energy Balances. The observed energy efficiency improvements range between 2.2 and 3.5% per year, i.e., they are on the higher side of the values typically reported in literature. Our results point to uncertainties in the basic chemical industry’s final energy use as reported in the energy statistics and the specific energy consumption values. More efforts are required to improve the quality of the national and international energy statistics to make them useable for reliable monitoring of energy efficiency improvements of the chemical industry. -- Highlights: ► An advanced model was developed to estimate German chemical industry’s energy use. ► For the base year (2000), model covers 88% of the sector’s total final energy use. ► Sector’s energy efficiency improved between 2.2 and 3.5%/yr between 1995 and 2008. ► Improved energy statistics are required for accurate monitoring of improvements.

Statistical calculation of hot channel factors

International Nuclear Information System (INIS)

Farhadi, K.

2007-01-01

It is a conventional practice in the design of nuclear reactors to introduce hot channel factors to allow for spatial variations of power generation and flow distribution. Consequently, it is not enough to be able to calculate the nominal temperature distributions of fuel element, cladding, coolant, and central fuel. Indeed, one must be able to calculate the probability that the imposed temperature or heat flux limits in the entire core is not exceeded. In this paper, statistical methods are used to calculate hot channel factors for a particular case of a heterogeneous, Material Testing Reactor (MTR) and compare the results obtained from different statistical methods. It is shown that among the statistical methods available, the semi-statistical method is the most reliable one

Testing statistical significance scores of sequence comparison methods with structure similarity

Directory of Open Access Journals (Sweden)

Leunissen Jack AM

2006-10-01

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

1992 Energy statistics Yearbook

International Nuclear Information System (INIS)

1994-01-01

The principal objective of the Yearbook is to provide a global framework of comparable data on long-term trends in the supply of mainly commercial primary and secondary forms of energy. Data for each type of fuel and aggregate data for the total mix of commercial fuels are shown for individual countries and areas and are summarized into regional and world totals. The data are compiled primarily from annual questionnaires distributed by the United Nations Statistical Division and supplemented by official national statistical publications. Where official data are not available or are inconsistent, estimates are made by the Statistical Division based on governmental, professional or commercial materials. Estimates include, but are not limited to, extrapolated data based on partial year information, use of annual trends, trade data based on partner country reports, breakdowns of aggregated data as well as analysis of current energy events and activities

Comparing Kaolin and Pinolene to Improve Sustainable Grapevine Production during Drought.

Science.gov (United States)

Brillante, Luca; Belfiore, Nicola; Gaiotti, Federica; Lovat, Lorenzo; Sansone, Luigi; Poni, Stefano; Tomasi, Diego

2016-01-01

Viticulture is widely practiced in dry regions, where the grapevine is greatly exposed to water stress. Optimizing plant water use efficiency (WUE) without affecting crop yield, grape and wine quality is crucial to limiting use of water for irrigation and to significantly improving viticulture sustainability. This study examines the use in vineyards of particle film technology (engineered kaolin) and compares it to a film-forming antitranspirant (pinolene), traditionally used to limit leaf water loss, and to an untreated control. The trial was carried out under field conditions over three growing seasons, during which moderate to very severe plant water stress (down to -1.9 MPa) was measured through stem water potential. Leaf stomatal conductance (gs) and photosynthesis rate (An) were measured during the seasons and used to compute intrinsic WUE (WUEi, defined as An/gs ratio). Leaf temperature was also recorded and compared between treatments. Bunch quantity, bunch and berry weight, sugar accumulation, anthocyanin and flavonoid contents were measured. Finally, microvinifications were performed and resultant wines subjected to sensory evaluation.Results showed that the use of kaolin increased grapevine intrinsic WUE (+18% on average as compared to unsprayed vines) without affecting berry and bunch weight and quantity, or sugar level. Anthocyanin content increased (+35%) in kaolin treatment, and the wine was judged more attractive (p-value wine was the least appreciated. This study demonstrates that particle film technology can improve vine WUEi and wine quality at the same time, while traditional antitranspirants were not as effective for these purposes. This positive effect can be used in interaction with other already-demonstrated uses of particle film technology, such as pest control and sunburn reduction, in order to achieve more sustainable vineyard management.

A framework for the economic analysis of data collection methods for vital statistics.

Science.gov (United States)

Jimenez-Soto, Eliana; Hodge, Andrew; Nguyen, Kim-Huong; Dettrick, Zoe; Lopez, Alan D

2014-01-01

Over recent years there has been a strong movement towards the improvement of vital statistics and other types of health data that inform evidence-based policies. Collecting such data is not cost free. To date there is no systematic framework to guide investment decisions on methods of data collection for vital statistics or health information in general. We developed a framework to systematically assess the comparative costs and outcomes/benefits of the various data methods for collecting vital statistics. The proposed framework is four-pronged and utilises two major economic approaches to systematically assess the available data collection methods: cost-effectiveness analysis and efficiency analysis. We built a stylised example of a hypothetical low-income country to perform a simulation exercise in order to illustrate an application of the framework. Using simulated data, the results from the stylised example show that the rankings of the data collection methods are not affected by the use of either cost-effectiveness or efficiency analysis. However, the rankings are affected by how quantities are measured. There have been several calls for global improvements in collecting useable data, including vital statistics, from health information systems to inform public health policies. Ours is the first study that proposes a systematic framework to assist countries undertake an economic evaluation of DCMs. Despite numerous challenges, we demonstrate that a systematic assessment of outputs and costs of DCMs is not only necessary, but also feasible. The proposed framework is general enough to be easily extended to other areas of health information.

Estimation of mouse organ locations through registration of a statistical mouse atlas with micro-CT images.

Science.gov (United States)

Wang, Hongkai; Stout, David B; Chatziioannou, Arion F

2012-01-01

Micro-CT is widely used in preclinical studies of small animals. Due to the low soft-tissue contrast in typical studies, segmentation of soft tissue organs from noncontrast enhanced micro-CT images is a challenging problem. Here, we propose an atlas-based approach for estimating the major organs in mouse micro-CT images. A statistical atlas of major trunk organs was constructed based on 45 training subjects. The statistical shape model technique was used to include inter-subject anatomical variations. The shape correlations between different organs were described using a conditional Gaussian model. For registration, first the high-contrast organs in micro-CT images were registered by fitting the statistical shape model, while the low-contrast organs were subsequently estimated from the high-contrast organs using the conditional Gaussian model. The registration accuracy was validated based on 23 noncontrast-enhanced and 45 contrast-enhanced micro-CT images. Three different accuracy metrics (Dice coefficient, organ volume recovery coefficient, and surface distance) were used for evaluation. The Dice coefficients vary from 0.45 ± 0.18 for the spleen to 0.90 ± 0.02 for the lungs, the volume recovery coefficients vary from 0.96 ± 0.10 for the liver to 1.30 ± 0.75 for the spleen, the surface distances vary from 0.18 ± 0.01 mm for the lungs to 0.72 ± 0.42 mm for the spleen. The registration accuracy of the statistical atlas was compared with two publicly available single-subject mouse atlases, i.e., the MOBY phantom and the DIGIMOUSE atlas, and the results proved that the statistical atlas is more accurate than the single atlases. To evaluate the influence of the training subject size, different numbers of training subjects were used for atlas construction and registration. The results showed an improvement of the registration accuracy when more training subjects were used for the atlas construction. The statistical atlas-based registration was also compared with

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

Directory of Open Access Journals (Sweden)

Melissa Coulson

2010-07-01

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

Drug supply indicators: Pitfalls and possibilities for improvements to assist comparative analysis.

Science.gov (United States)

Singleton, Nicola; Cunningham, Andrew; Groshkova, Teodora; Royuela, Luis; Sedefov, Roumen

2018-06-01

Interventions to tackle the supply of drugs are seen as standard components of illicit drug policies. Therefore drug market-related administrative data, such as seizures, price, purity and drug-related offending, are used in most countries for policy monitoring and assessment of the drug situation. International agencies, such as the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) and the UN Office of Drugs and Crime, also monitor and report on the drug situation cross-nationally and therefore seek to collect and make available key data in a uniform manner from the countries they cover. However, these data are not primarily collected for this purpose, which makes interpretation and comparative analysis difficult. Examples of limitations of these data sources include: the extent to which they reflect operational priorities rather than market changes; question marks over the robustness of and consistency in data collection methods, and issues around the timeliness of data availability. Such problems are compounded by cultural, social and contextual differences between countries. Making sense of such data is therefore challenging and extreme care needs to be taken using it. Nevertheless, these data provide an important window on a hidden area, so improving the quality of the data collected and expanding its scope should be a priority for those seeking to understand or monitor drug markets and supply reduction. In addition to highlighting some of the potential pitfalls in using supply indicators for comparative analysis, this paper presents a selection of options for improvements based on the current EMCDDA programme of work to improve their supply-related monitoring and analysis. The conceptual framework developed to steer this work may have wider application. Adopting this approach has the potential to provide a richer picture of drug markets, at both national and international levels, and make it easier to compare data between countries. Copyright �

Environmental accounting and statistics

International Nuclear Information System (INIS)

Bartelmus, P.L.P.

1992-01-01

The objective of sustainable development is to integrate environmental concerns with mainstream socio-economic policies. Integrated policies need to be supported by integrated data. Environmental accounting achieves this integration by incorporating environmental costs and benefits into conventional national accounts. Modified accounting aggregates can thus be used in defining and measuring environmentally sound and sustainable economic growth. Further development objectives need to be assessed by more comprehensive, though necessarily less integrative, systems of environmental statistics and indicators. Integrative frameworks for the different statistical systems in the fields of economy, environment and population would facilitate the provision of comparable data for the analysis of integrated development. (author). 19 refs, 2 figs, 2 tabs

Usage statistics and demonstrator services

CERN Multimedia

CERN. Geneva

2007-01-01

An understanding of the use of repositories and their contents is clearly desirable for authors and repository managers alike, as well as those who are analysing the state of scholarly communications. A number of individual initiatives have produced statistics of variious kinds for individual repositories, but the real challenge is to produce statistics that can be collected and compared transparently on a global scale. This presentation details the steps to be taken to address the issues to attain this capability View Les Carr's biography

Instruction in Information Structuring Improves Bayesian Judgment in Intelligence Analysts

Directory of Open Access Journals (Sweden)

David R. Mandel

2015-04-01

Full Text Available An experiment was conducted to test the effectiveness of brief instruction in information structuring (i.e., representing and integrating information for improving the coherence of probability judgments and binary choices among intelligence analysts. Forty-three analysts were presented with comparable sets of Bayesian judgment problems before and immediately after instruction. After instruction, analysts’ probability judgments were more coherent (i.e., more additive and compliant with Bayes theorem. Instruction also improved the coherence of binary choices regarding category membership: after instruction, subjects were more likely to invariably choose the category to which they assigned the higher probability of a target’s membership. The research provides a rare example of evidence-based validation of effectiveness in instruction to improve the statistical assessment skills of intelligence analysts. Such instruction could also be used to improve the assessment quality of other types of experts who are required to integrate statistical information or make probabilistic assessments.

Adaptive Maneuvering Frequency Method of Current Statistical Model

Institute of Scientific and Technical Information of China (English)

Wei Sun; Yongjian Yang

2017-01-01

Current statistical model(CSM) has a good performance in maneuvering target tracking. However, the fixed maneuvering frequency will deteriorate the tracking results, such as a serious dynamic delay, a slowly converging speedy and a limited precision when using Kalman filter(KF) algorithm. In this study, a new current statistical model and a new Kalman filter are proposed to improve the performance of maneuvering target tracking. The new model which employs innovation dominated subjection function to adaptively adjust maneuvering frequency has a better performance in step maneuvering target tracking, while a fluctuant phenomenon appears. As far as this problem is concerned, a new adaptive fading Kalman filter is proposed as well. In the new Kalman filter, the prediction values are amended in time by setting judgment and amendment rules,so that tracking precision and fluctuant phenomenon of the new current statistical model are improved. The results of simulation indicate the effectiveness of the new algorithm and the practical guiding significance.

Comparative effectiveness of open versus minimally invasive sacroiliac joint fusion.

Science.gov (United States)

Ledonio, Charles Gt; Polly, David W; Swiontkowski, Marc F; Cummings, John T

2014-01-01

The mainstay of sacroiliac joint disruption/degenerative sacroiliitis therapy has been nonoperative management. This nonoperative management often includes a regimen of physical therapy, chiropractic treatment, therapeutic injections, and possibly radiofrequency ablation at the discretion of the treating physician. When these clinical treatments fail, sacroiliac joint fusion has been recommended as the standard treatment. Open and minimally invasive (MIS) surgical techniques are typical procedures. This study aims to compare the perioperative measures and Oswestry Disability Index (ODI) outcomes associated with each of these techniques. A comparative retrospective chart review of patients with sacroiliac joint fusion and a minimum of 1 year of follow-up was performed. Perioperative measures and ODI scores were compared using the Fisher's exact test and two nonparametric tests, ie, the Mann-Whitney U test and the Wilcoxon signed-rank test. The results are presented as percent or median with range, as appropriate. Forty-nine patients from two institutions underwent sacroiliac joint fusion between 2006 and 2012. Ten patients were excluded because of incomplete data, leaving 39 evaluable patients, of whom 22 underwent open and 17 underwent MIS sacroiliac joint fusion. The MIS group was significantly older (median age 66 [39-82] years) than the open group (median age 51 [34-74] years). Surgical time and hospital stay were significantly shorter in the MIS group than in the open group. Preoperative ODI was significantly greater in the open group (median 64 [44-78]) than in the MIS group (median 53 [14-84]). Postoperative improvement in ODI was statistically significant within and between groups, with MIS resulting in greater improvement. The open and MIS sacroiliac joint fusion techniques resulted in statistically and clinically significant improvement for patients with degenerative sacroiliitis refractory to nonoperative management. However, the number of patients

Analysis of uncertainties and convergence of the statistical quantities in turbulent wall-bounded flows by means of a physically based criterion

Science.gov (United States)

Andrade, João Rodrigo; Martins, Ramon Silva; Thompson, Roney Leon; Mompean, Gilmar; da Silveira Neto, Aristeu

2018-04-01

The present paper provides an analysis of the statistical uncertainties associated with direct numerical simulation (DNS) results and experimental data for turbulent channel and pipe flows, showing a new physically based quantification of these errors, to improve the determination of the statistical deviations between DNSs and experiments. The analysis is carried out using a recently proposed criterion by Thompson et al. ["A methodology to evaluate statistical errors in DNS data of plane channel flows," Comput. Fluids 130, 1-7 (2016)] for fully turbulent plane channel flows, where the mean velocity error is estimated by considering the Reynolds stress tensor, and using the balance of the mean force equation. It also presents how the residual error evolves in time for a DNS of a plane channel flow, and the influence of the Reynolds number on its convergence rate. The root mean square of the residual error is shown in order to capture a single quantitative value of the error associated with the dimensionless averaging time. The evolution in time of the error norm is compared with the final error provided by DNS data of similar Reynolds numbers available in the literature. A direct consequence of this approach is that it was possible to compare different numerical results and experimental data, providing an improved understanding of the convergence of the statistical quantities in turbulent wall-bounded flows.

Antibiotic Resistome: Improving Detection and Quantification Accuracy for Comparative Metagenomics.

Science.gov (United States)

Elbehery, Ali H A; Aziz, Ramy K; Siam, Rania

2016-04-01

The unprecedented rise of life-threatening antibiotic resistance (AR), combined with the unparalleled advances in DNA sequencing of genomes and metagenomes, has pushed the need for in silico detection of the resistance potential of clinical and environmental metagenomic samples through the quantification of AR genes (i.e., genes conferring antibiotic resistance). Therefore, determining an optimal methodology to quantitatively and accurately assess AR genes in a given environment is pivotal. Here, we optimized and improved existing AR detection methodologies from metagenomic datasets to properly consider AR-generating mutations in antibiotic target genes. Through comparative metagenomic analysis of previously published AR gene abundance in three publicly available metagenomes, we illustrate how mutation-generated resistance genes are either falsely assigned or neglected, which alters the detection and quantitation of the antibiotic resistome. In addition, we inspected factors influencing the outcome of AR gene quantification using metagenome simulation experiments, and identified that genome size, AR gene length, total number of metagenomics reads and selected sequencing platforms had pronounced effects on the level of detected AR. In conclusion, our proposed improvements in the current methodologies for accurate AR detection and resistome assessment show reliable results when tested on real and simulated metagenomic datasets.

Comparative Analysis of Kernel Methods for Statistical Shape Learning

National Research Council Canada - National Science Library

Rathi, Yogesh; Dambreville, Samuel; Tannenbaum, Allen

2006-01-01

.... In this work, we perform a comparative analysis of shape learning techniques such as linear PCA, kernel PCA, locally linear embedding and propose a new method, kernelized locally linear embedding...

Comparing and improving reconstruction methods for proxies based on compositional data

Science.gov (United States)

Nolan, C.; Tipton, J.; Booth, R.; Jackson, S. T.; Hooten, M.

2017-12-01

Many types of studies in paleoclimatology and paleoecology involve compositional data. Often, these studies aim to use compositional data to reconstruct an environmental variable of interest; the reconstruction is usually done via the development of a transfer function. Transfer functions have been developed using many different methods. Existing methods tend to relate the compositional data and the reconstruction target in very simple ways. Additionally, the results from different methods are rarely compared. Here we seek to address these two issues. First, we introduce a new hierarchical Bayesian multivariate gaussian process model; this model allows for the relationship between each species in the compositional dataset and the environmental variable to be modeled in a way that captures the underlying complexities. Then, we compare this new method to machine learning techniques and commonly used existing methods. The comparisons are based on reconstructing the water table depth history of Caribou Bog (an ombrotrophic Sphagnum peat bog in Old Town, Maine, USA) from a new 7500 year long record of testate amoebae assemblages. The resulting reconstructions from different methods diverge in both their resulting means and uncertainties. In particular, uncertainty tends to be drastically underestimated by some common methods. These results will help to improve inference of water table depth from testate amoebae. Furthermore, this approach can be applied to test and improve inferences of past environmental conditions from a broad array of paleo-proxies based on compositional data

Securing an OTL-HNS residency: how competitive is it? Comparing medical student perceptions to actual Canadian statistics.

Science.gov (United States)

Kay-Rivest, E; Varma, N; Scott, G M; Manoukian, J J; Desrosiers, M; Vaccani, J P; Nguyen, L H P

2017-02-27

The residency match is an important event in an aspiring physician's career. Otolaryngology - Head and Neck Surgery (OTL-HNS) is a surgical specialty that has enjoyed high numbers of applicants to its residency programs. However, recent trends in Canada show a decline in first-choice applicants to several surgical fields. Factors thought to influence a medical student's choice include role models, career opportunities and work-life balance. The notion of perceived competitiveness is a factor that has not yet been explored. This study sought to compare competitiveness of OTL-HNS, as perceived by Canadian medical students to residency match statistics published yearly by CaRMS (Canadian Residency Matching Service), with the hope of informing future decisions of surgical residency programs. An electronic survey was created and distributed to all medical students enrolled in the 17 Canadian medical schools. After gathering demographic information, students were asked to rank what they perceived to be the five most competitive disciplines offered by CaRMS. They were also asked to rank surgical specialties from most to least competitive. Publically available data from CaRMS was then collected and analyzed to determine actual competitiveness of admissions to Canadian OTL-HNS residency programs. 1194 students, from first to fourth year of medical school, completed the survey. CaRMS statistics over the period from 2008 to 2014 demonstrated that the five most competitive specialties were Plastic Surgery, Dermatology, Ophthalmology, Emergency Medicine and OTL-HNS. Among surgical disciplines, OTL-HNS was third most competitive, where on average 72% of students match to their first-choice discipline. When students were questioned, 35% ranked OTL-HNS amongst the top five most competitive. On the other hand 72%, 74% and 80% recognized Opthalmology, Dermatology and Plastic Surgery as being among the five most competitive, respectively. We found that fourth-year medical students

Improve projections of changes in southern African summer rainfall through comprehensive multi-timescale empirical statistical downscaling

Science.gov (United States)

Dieppois, B.; Pohl, B.; Eden, J.; Crétat, J.; Rouault, M.; Keenlyside, N.; New, M. G.

2017-12-01

simulate southern African summer rainfall. This multi-timescale procedure shows much better skills in simulating decadal timescales of variability compared to commonly used statistical downscaling approaches.

Increased Statistical Efficiency in a Lognormal Mean Model

Directory of Open Access Journals (Sweden)

Grant H. Skrepnek

2014-01-01

Full Text Available Within the context of clinical and other scientific research, a substantial need exists for an accurate determination of the point estimate in a lognormal mean model, given that highly skewed data are often present. As such, logarithmic transformations are often advocated to achieve the assumptions of parametric statistical inference. Despite this, existing approaches that utilize only a sample’s mean and variance may not necessarily yield the most efficient estimator. The current investigation developed and tested an improved efficient point estimator for a lognormal mean by capturing more complete information via the sample’s coefficient of variation. Results of an empirical simulation study across varying sample sizes and population standard deviations indicated relative improvements in efficiency of up to 129.47 percent compared to the usual maximum likelihood estimator and up to 21.33 absolute percentage points above the efficient estimator presented by Shen and colleagues (2006. The relative efficiency of the proposed estimator increased particularly as a function of decreasing sample size and increasing population standard deviation.

CYberinfrastructure for COmparative effectiveness REsearch (CYCORE): improving data from cancer clinical trials

OpenAIRE

Patrick, Kevin; Wolszon, Laura; Basen-Engquist, Karen M; Demark-Wahnefried, Wendy; Prokhorov, Alex V; Barrera, Stephanie; Baru, Chaitan; Farcas, Emilia; Krueger, Ingolf; Palmer, Doug; Raab, Fred; Rios, Phil; Ziftci, Celal; Peterson, Susan

2010-01-01

ABSTRACT Improved approaches and methodologies are needed to conduct comparative effectiveness research (CER) in oncology. While cancer therapies continue to emerge at a rapid pace, the review, synthesis, and dissemination of evidence-based interventions across clinical trials lag in comparison. Rigorous and systematic testing of competing therapies has been clouded by age-old problems: poor patient adherence, inability to objectively measure the environmental influences on health, lack of kn...

Statistical Model of Extreme Shear

DEFF Research Database (Denmark)

Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

2005-01-01

In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describes the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of full-scale measurements recorded with a high sampling rate...

Semiclassical analysis, Witten Laplacians, and statistical mechanis

CERN Document Server

Helffer, Bernard

2002-01-01

This important book explains how the technique of Witten Laplacians may be useful in statistical mechanics. It considers the problem of analyzing the decay of correlations, after presenting its origin in statistical mechanics. In addition, it compares the Witten Laplacian approach with other techniques, such as the transfer matrix approach and its semiclassical analysis. The author concludes by providing a complete proof of the uniform Log-Sobolev inequality. Contents: Witten Laplacians Approach; Problems in Statistical Mechanics with Discrete Spins; Laplace Integrals and Transfer Operators; S

A Survey of Statistical Machine Translation

Science.gov (United States)

2007-04-01

methods are notoriously sen- sitive to domain differences, however, so the move to informal text is likely to present many interesting challenges ...Och, Christoph Tillman, and Hermann Ney. Improved alignment models for statistical machine translation. In Proc. of EMNLP- VLC , pages 20–28, Jun 1999

Statistical thermodynamics

International Nuclear Information System (INIS)

Lim, Gyeong Hui

2008-03-01

This book consists of 15 chapters, which are basic conception and meaning of statistical thermodynamics, Maxwell-Boltzmann's statistics, ensemble, thermodynamics function and fluctuation, statistical dynamics with independent particle system, ideal molecular system, chemical equilibrium and chemical reaction rate in ideal gas mixture, classical statistical thermodynamics, ideal lattice model, lattice statistics and nonideal lattice model, imperfect gas theory on liquid, theory on solution, statistical thermodynamics of interface, statistical thermodynamics of a high molecule system and quantum statistics

Inference on network statistics by restricting to the network space: applications to sexual history data.

Science.gov (United States)

Goyal, Ravi; De Gruttola, Victor

2018-01-30

Analysis of sexual history data intended to describe sexual networks presents many challenges arising from the fact that most surveys collect information on only a very small fraction of the population of interest. In addition, partners are rarely identified and responses are subject to reporting biases. Typically, each network statistic of interest, such as mean number of sexual partners for men or women, is estimated independently of other network statistics. There is, however, a complex relationship among networks statistics; and knowledge of these relationships can aid in addressing concerns mentioned earlier. We develop a novel method that constrains a posterior predictive distribution of a collection of network statistics in order to leverage the relationships among network statistics in making inference about network properties of interest. The method ensures that inference on network properties is compatible with an actual network. Through extensive simulation studies, we also demonstrate that use of this method can improve estimates in settings where there is uncertainty that arises both from sampling and from systematic reporting bias compared with currently available approaches to estimation. To illustrate the method, we apply it to estimate network statistics using data from the Chicago Health and Social Life Survey. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Weighted statistical parameters for irregularly sampled time series

Science.gov (United States)

Rimoldini, Lorenzo

2014-01-01

Unevenly spaced time series are common in astronomy because of the day-night cycle, weather conditions, dependence on the source position in the sky, allocated telescope time and corrupt measurements, for example, or inherent to the scanning law of satellites like Hipparcos and the forthcoming Gaia. Irregular sampling often causes clumps of measurements and gaps with no data which can severely disrupt the values of estimators. This paper aims at improving the accuracy of common statistical parameters when linear interpolation (in time or phase) can be considered an acceptable approximation of a deterministic signal. A pragmatic solution is formulated in terms of a simple weighting scheme, adapting to the sampling density and noise level, applicable to large data volumes at minimal computational cost. Tests on time series from the Hipparcos periodic catalogue led to significant improvements in the overall accuracy and precision of the estimators with respect to the unweighted counterparts and those weighted by inverse-squared uncertainties. Automated classification procedures employing statistical parameters weighted by the suggested scheme confirmed the benefits of the improved input attributes. The classification of eclipsing binaries, Mira, RR Lyrae, Delta Cephei and Alpha2 Canum Venaticorum stars employing exclusively weighted descriptive statistics achieved an overall accuracy of 92 per cent, about 6 per cent higher than with unweighted estimators.

MANUFACTURING AND CONTINUOUS IMPROVEMENT PERFORMANCE LEVEL IN PLANTS OF MEXICO; A COMPARATIVE ANALYSIS AMONG LARGE AND MEDIUM SIZE PLANTS

OpenAIRE

Carlos Monge; Jesús Cruz

2015-01-01

A random and statistically significant sample of 40 medium (12) and large (28) manufacturing plants of Apodaca, Mexico were surveyed using a structured and validated questionnaire to investigate the level of implementation of lean manufacturing, sustainable manufacturing, continuous improvement and operational efficiency and environmental responsibility in them, it is important to mention it was found that performance in the mentioned philosophies, on the two categories of plants is low, howe...

Planning ability improves in a yogic education system compared to a modern.

Science.gov (United States)

Rangan, R; Nagendra, H R; Bhat, G Ramachandra

2008-07-01

Planning skills play a key role in higher developmental processes. The Tower of London test not only measures planning skills, but also the ability to execute plans. Yoga practices aim to bring about higher development. Can a Yoga-based education system be shown to meet this challenge? This study was aimed at comparing a Modern Education System (MES) with the ancient Yoga-based system of education, the Gurukula Education System (GES), in developing planning skills. Forty-nine boys with ages ranging from 11 to 13 years were selected from each of two residential schools, one MES and the other GES, providing similar ambience and daily routines. The boys were matched for age and socio-economic status. The GES educational program is based around integrated yoga modules while the MES provides a conventional modern education program. Planning and executive abilities were assessed using the Tower of London test at the start and the end of an academic year. Within groups, the pre-post test differences were significant for both groups. However, the between-groups results showed improvement in the GES group compared to the MES group at a P education improve planning and execution skills in school boys, GES is more effective of the two systems.

Using Statistical Process Control to Make Data-Based Clinical Decisions.

Science.gov (United States)

Pfadt, Al; Wheeler, Donald J.

1995-01-01

Statistical process control (SPC), which employs simple statistical tools and problem-solving techniques such as histograms, control charts, flow charts, and Pareto charts to implement continual product improvement procedures, can be incorporated into human service organizations. Examples illustrate use of SPC procedures to analyze behavioral data…

[Statistics for statistics?--Thoughts about psychological tools].

Science.gov (United States)

Berger, Uwe; Stöbel-Richter, Yve

2007-12-01

Statistical methods take a prominent place among psychologists' educational programs. Being known as difficult to understand and heavy to learn, students fear of these contents. Those, who do not aspire after a research carrier at the university, will forget the drilled contents fast. Furthermore, because it does not apply for the work with patients and other target groups at a first glance, the methodological education as a whole was often questioned. For many psychological practitioners the statistical education makes only sense by enforcing respect against other professions, namely physicians. For the own business, statistics is rarely taken seriously as a professional tool. The reason seems to be clear: Statistics treats numbers, while psychotherapy treats subjects. So, does statistics ends in itself? With this article, we try to answer the question, if and how statistical methods were represented within the psychotherapeutical and psychological research. Therefore, we analyzed 46 Originals of a complete volume of the journal Psychotherapy, Psychosomatics, Psychological Medicine (PPmP). Within the volume, 28 different analyse methods were applied, from which 89 per cent were directly based upon statistics. To be able to write and critically read Originals as a backbone of research, presumes a high degree of statistical education. To ignore statistics means to ignore research and at least to reveal the own professional work to arbitrariness.

An Improved Statistical Point-source Foreground Model for the Epoch of Reionization

Energy Technology Data Exchange (ETDEWEB)

Murray, S. G.; Trott, C. M.; Jordan, C. H. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia)

2017-08-10

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.

An Improved Statistical Point-source Foreground Model for the Epoch of Reionization

Science.gov (United States)

Murray, S. G.; Trott, C. M.; Jordan, C. H.

2017-08-01

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.

Reliability Evaluation of Concentric Butterfly Valve Using Statistical Hypothesis Test

Energy Technology Data Exchange (ETDEWEB)

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

2015-12-15

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

Reliability Evaluation of Concentric Butterfly Valve Using Statistical Hypothesis Test

International Nuclear Information System (INIS)

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

2015-01-01

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

Statistical analysis of the Ft. Calhoun reactor coolant pump system

International Nuclear Information System (INIS)

Patel, Bimal; Heising, C.D.

1997-01-01

In engineering science, statistical quality control techniques have traditionally been applied to control manufacturing processes. An application to commercial nuclear power plant maintenance and control is presented that can greatly improve plant safety. As a demonstration of such an approach, a specific system is analyzed: the reactor coolant pumps (RCPs) of the Ft. Calhoun nuclear power plant. This research uses capability analysis, Shewhart X-bar, R charts, canonical correlation methods, and design of experiments to analyze the process for the state of statistical control. The results obtained show that six out of ten parameters are under control specification limits and four parameters are not in the state of statistical control. The analysis shows that statistical process control methods can be applied as an early warning system capable of identifying significant equipment problems well in advance of traditional control room alarm indicators. Such a system would provide operators with ample time to respond to possible emergency situations and thus improve plant safety and reliability. (Author)

Short-Term Solar Irradiance Forecasting Model Based on Artificial Neural Network Using Statistical Feature Parameters

Directory of Open Access Journals (Sweden)

Hongshan Zhao

2012-05-01

Full Text Available Short-term solar irradiance forecasting (STSIF is of great significance for the optimal operation and power predication of grid-connected photovoltaic (PV plants. However, STSIF is very complex to handle due to the random and nonlinear characteristics of solar irradiance under changeable weather conditions. Artificial Neural Network (ANN is suitable for STSIF modeling and many research works on this topic are presented, but the conciseness and robustness of the existing models still need to be improved. After discussing the relation between weather variations and irradiance, the characteristics of the statistical feature parameters of irradiance under different weather conditions are figured out. A novel ANN model using statistical feature parameters (ANN-SFP for STSIF is proposed in this paper. The input vector is reconstructed with several statistical feature parameters of irradiance and ambient temperature. Thus sufficient information can be effectively extracted from relatively few inputs and the model complexity is reduced. The model structure is determined by cross-validation (CV, and the Levenberg-Marquardt algorithm (LMA is used for the network training. Simulations are carried out to validate and compare the proposed model with the conventional ANN model using historical data series (ANN-HDS, and the results indicated that the forecast accuracy is obviously improved under variable weather conditions.

Teaching biology through statistics: application of statistical methods in genetics and zoology courses.

Science.gov (United States)

Colon-Berlingeri, Migdalisel; Burrowes, Patricia A

2011-01-01

Incorporation of mathematics into biology curricula is critical to underscore for undergraduate students the relevance of mathematics to most fields of biology and the usefulness of developing quantitative process skills demanded in modern biology. At our institution, we have made significant changes to better integrate mathematics into the undergraduate biology curriculum. The curricular revision included changes in the suggested course sequence, addition of statistics and precalculus as prerequisites to core science courses, and incorporating interdisciplinary (math-biology) learning activities in genetics and zoology courses. In this article, we describe the activities developed for these two courses and the assessment tools used to measure the learning that took place with respect to biology and statistics. We distinguished the effectiveness of these learning opportunities in helping students improve their understanding of the math and statistical concepts addressed and, more importantly, their ability to apply them to solve a biological problem. We also identified areas that need emphasis in both biology and mathematics courses. In light of our observations, we recommend best practices that biology and mathematics academic departments can implement to train undergraduates for the demands of modern biology.

Statistical Symbolic Execution with Informed Sampling

Science.gov (United States)

Filieri, Antonio; Pasareanu, Corina S.; Visser, Willem; Geldenhuys, Jaco

2014-01-01

Symbolic execution techniques have been proposed recently for the probabilistic analysis of programs. These techniques seek to quantify the likelihood of reaching program events of interest, e.g., assert violations. They have many promising applications but have scalability issues due to high computational demand. To address this challenge, we propose a statistical symbolic execution technique that performs Monte Carlo sampling of the symbolic program paths and uses the obtained information for Bayesian estimation and hypothesis testing with respect to the probability of reaching the target events. To speed up the convergence of the statistical analysis, we propose Informed Sampling, an iterative symbolic execution that first explores the paths that have high statistical significance, prunes them from the state space and guides the execution towards less likely paths. The technique combines Bayesian estimation with a partial exact analysis for the pruned paths leading to provably improved convergence of the statistical analysis. We have implemented statistical symbolic execution with in- formed sampling in the Symbolic PathFinder tool. We show experimentally that the informed sampling obtains more precise results and converges faster than a purely statistical analysis and may also be more efficient than an exact symbolic analysis. When the latter does not terminate symbolic execution with informed sampling can give meaningful results under the same time and memory limits.

Statistical learning methods in high-energy and astrophysics analysis

Energy Technology Data Exchange (ETDEWEB)

Zimmermann, J. [Forschungszentrum Juelich GmbH, Zentrallabor fuer Elektronik, 52425 Juelich (Germany) and Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Munich (Germany)]. E-mail: zimmerm@mppmu.mpg.de; Kiesling, C. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Munich (Germany)

2004-11-21

We discuss several popular statistical learning methods used in high-energy- and astro-physics analysis. After a short motivation for statistical learning we present the most popular algorithms and discuss several examples from current research in particle- and astro-physics. The statistical learning methods are compared with each other and with standard methods for the respective application.

Statistical learning methods in high-energy and astrophysics analysis

International Nuclear Information System (INIS)

Zimmermann, J.; Kiesling, C.

2004-01-01

We discuss several popular statistical learning methods used in high-energy- and astro-physics analysis. After a short motivation for statistical learning we present the most popular algorithms and discuss several examples from current research in particle- and astro-physics. The statistical learning methods are compared with each other and with standard methods for the respective application

Statistical considerations in the development of injury risk functions.

Science.gov (United States)

McMurry, Timothy L; Poplin, Gerald S

2015-01-01

We address 4 frequently misunderstood and important statistical ideas in the construction of injury risk functions. These include the similarities of survival analysis and logistic regression, the correct scale on which to construct pointwise confidence intervals for injury risk, the ability to discern which form of injury risk function is optimal, and the handling of repeated tests on the same subject. The statistical models are explored through simulation and examination of the underlying mathematics. We provide recommendations for the statistically valid construction and correct interpretation of single-predictor injury risk functions. This article aims to provide useful and understandable statistical guidance to improve the practice in constructing injury risk functions.

Understanding common statistical methods, Part I: descriptive methods, probability, and continuous data.

Science.gov (United States)

Skinner, Carl G; Patel, Manish M; Thomas, Jerry D; Miller, Michael A

2011-01-01

Statistical methods are pervasive in medical research and general medical literature. Understanding general statistical concepts will enhance our ability to critically appraise the current literature and ultimately improve the delivery of patient care. This article intends to provide an overview of the common statistical methods relevant to medicine.

Application of blended learning in teaching statistical methods

Directory of Open Access Journals (Sweden)

Barbara Dębska

2012-12-01

Full Text Available The paper presents the application of a hybrid method (blended learning - linking traditional education with on-line education to teach selected problems of mathematical statistics. This includes the teaching of the application of mathematical statistics to evaluate laboratory experimental results. An on-line statistics course was developed to form an integral part of the module ‘methods of statistical evaluation of experimental results’. The course complies with the principles outlined in the Polish National Framework of Qualifications with respect to the scope of knowledge, skills and competencies that students should have acquired at course completion. The paper presents the structure of the course and the educational content provided through multimedia lessons made accessible on the Moodle platform. Following courses which used the traditional method of teaching and courses which used the hybrid method of teaching, students test results were compared and discussed to evaluate the effectiveness of the hybrid method of teaching when compared to the effectiveness of the traditional method of teaching.

Visual Acuity Improvement in Continuous vs Divided Occlusion in Anisometropic Amblyopia.

Science.gov (United States)

Irfani, Irawati; Feriyanto, Feri; Oktarima, Primawita; Kartasasmita, Arief

2018-01-01

To compare visual acuity improvement between continuous and split part-time occlusion for the treatment of moderate and severe anisometropic amblyopia. Randomised clinical trials in 6 - 13 y.o children with moderate and severe anisometropic amblyopia. Each patient was consecutively selected with continuous or split part-time occlusion. Best corrected visual acuity's improvement was followed up to six weeks and statistical data were analyzed using chi square and unpaired t-test. Best corrected visual acuity's improvement was comparable between continuous and split part-time occlusion (0.20±0.27 vs 0.21±0.25; p = 0.79). Split part-time occlusion may be considered as an alternative treatment for moderate and severe anisometropic amblyopia treatment.

Statistical modelling for recurrent events: an application to sports injuries.

Science.gov (United States)

Ullah, Shahid; Gabbett, Tim J; Finch, Caroline F

2014-09-01

Injuries are often recurrent, with subsequent injuries influenced by previous occurrences and hence correlation between events needs to be taken into account when analysing such data. This paper compares five different survival models (Cox proportional hazards (CoxPH) model and the following generalisations to recurrent event data: Andersen-Gill (A-G), frailty, Wei-Lin-Weissfeld total time (WLW-TT) marginal, Prentice-Williams-Peterson gap time (PWP-GT) conditional models) for the analysis of recurrent injury data. Empirical evaluation and comparison of different models were performed using model selection criteria and goodness-of-fit statistics. Simulation studies assessed the size and power of each model fit. The modelling approach is demonstrated through direct application to Australian National Rugby League recurrent injury data collected over the 2008 playing season. Of the 35 players analysed, 14 (40%) players had more than 1 injury and 47 contact injuries were sustained over 29 matches. The CoxPH model provided the poorest fit to the recurrent sports injury data. The fit was improved with the A-G and frailty models, compared to WLW-TT and PWP-GT models. Despite little difference in model fit between the A-G and frailty models, in the interest of fewer statistical assumptions it is recommended that, where relevant, future studies involving modelling of recurrent sports injury data use the frailty model in preference to the CoxPH model or its other generalisations. The paper provides a rationale for future statistical modelling approaches for recurrent sports injury. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Kepler Planet Detection Metrics: Statistical Bootstrap Test

Science.gov (United States)

Jenkins, Jon M.; Burke, Christopher J.

2016-01-01

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

Sub-Poissonian statistics in order-to-chaos transition

International Nuclear Information System (INIS)

Kryuchkyan, Gagik Yu.; Manvelyan, Suren B.

2003-01-01

We study the phenomena at the overlap of quantum chaos and nonclassical statistics for the time-dependent model of nonlinear oscillator. It is shown in the framework of Mandel Q parameter and Wigner function that the statistics of oscillatory excitation numbers is drastically changed in the order-to-chaos transition. The essential improvement of sub-Poissonian statistics in comparison with an analogous one for the standard model of driven anharmonic oscillator is observed for the regular operational regime. It is shown that in the chaotic regime, the system exhibits the range of sub-Poissonian and super-Poissonian statistics which alternate one to other depending on time intervals. Unusual dependence of the variance of oscillatory number on the external noise level for the chaotic dynamics is observed. The scaling invariance of the quantum statistics is demonstrated and its relation to dissipation and decoherence is studied

Application of Parallel Hierarchical Matrices in Spatial Statistics and Parameter Identification

KAUST Repository

Litvinenko, Alexander

2018-04-20

Parallel H-matrices in spatial statistics 1. Motivation: improve statistical model 2. Tools: Hierarchical matrices [Hackbusch 1999] 3. Matern covariance function and joint Gaussian likelihood 4. Identification of unknown parameters via maximizing Gaussian log-likelihood 5. Implementation with HLIBPro

Brachytherapy Improves Biochemical Failure–Free Survival in Low- and Intermediate-Risk Prostate Cancer Compared With Conventionally Fractionated External Beam Radiation Therapy: A Propensity Score Matched Analysis

International Nuclear Information System (INIS)

Smith, Graham D.; Pickles, Tom; Crook, Juanita; Martin, Andre-Guy; Vigneault, Eric; Cury, Fabio L.; Morris, Jim; Catton, Charles; Lukka, Himu; Warner, Andrew; Yang, Ying; Rodrigues, George

2015-01-01

Purpose: To compare, in a retrospective study, biochemical failure-free survival (bFFS) and overall survival (OS) in low-risk and intermediate-risk prostate cancer patients who received brachytherapy (BT) (either low-dose-rate brachytherapy [LDR-BT] or high-dose-rate brachytherapy with external beam radiation therapy [HDR-BT+EBRT]) versus external beam radiation therapy (EBRT) alone. Methods and Materials: Patient data were obtained from the ProCaRS database, which contains 7974 prostate cancer patients treated with primary radiation therapy at four Canadian cancer institutions from 1994 to 2010. Propensity score matching was used to obtain the following 3 matched cohorts with balanced baseline prognostic factors: (1) low-risk LDR-BT versus EBRT; (2) intermediate-risk LDR-BT versus EBRT; and (3) intermediate-risk HDR-BT+EBRT versus EBRT. Kaplan-Meier survival analysis was performed to compare differences in bFFS (primary endpoint) and OS in the 3 matched groups. Results: Propensity score matching created acceptable balance in the baseline prognostic factors in all matches. Final matches included 2 1:1 matches in the intermediate-risk cohorts, LDR-BT versus EBRT (total n=254) and HDR-BT+EBRT versus EBRT (total n=388), and one 4:1 match in the low-risk cohort (LDR-BT:EBRT, total n=400). Median follow-up ranged from 2.7 to 7.3 years for the 3 matched cohorts. Kaplan-Meier survival analysis showed that all BT treatment options were associated with statistically significant improvements in bFFS when compared with EBRT in all cohorts (intermediate-risk EBRT vs LDR-BT hazard ratio [HR] 4.58, P=.001; intermediate-risk EBRT vs HDR-BT+EBRT HR 2.08, P=.007; low-risk EBRT vs LDR-BT HR 2.90, P=.004). No significant difference in OS was found in all comparisons (intermediate-risk EBRT vs LDR-BT HR 1.27, P=.687; intermediate-risk EBRT vs HDR-BT+EBRT HR 1.55, P=.470; low-risk LDR-BT vs EBRT HR 1.41, P=.500). Conclusions: Propensity score matched analysis showed that BT options led

Calculating statistical distributions from operator relations: The statistical distributions of various intermediate statistics

International Nuclear Information System (INIS)

Dai, Wu-Sheng; Xie, Mi

2013-01-01

In this paper, we give a general discussion on the calculation of the statistical distribution from a given operator relation of creation, annihilation, and number operators. Our result shows that as long as the relation between the number operator and the creation and annihilation operators can be expressed as a † b=Λ(N) or N=Λ −1 (a † b), where N, a † , and b denote the number, creation, and annihilation operators, i.e., N is a function of quadratic product of the creation and annihilation operators, the corresponding statistical distribution is the Gentile distribution, a statistical distribution in which the maximum occupation number is an arbitrary integer. As examples, we discuss the statistical distributions corresponding to various operator relations. In particular, besides the Bose–Einstein and Fermi–Dirac cases, we discuss the statistical distributions for various schemes of intermediate statistics, especially various q-deformation schemes. Our result shows that the statistical distributions corresponding to various q-deformation schemes are various Gentile distributions with different maximum occupation numbers which are determined by the deformation parameter q. This result shows that the results given in much literature on the q-deformation distribution are inaccurate or incomplete. -- Highlights: ► A general discussion on calculating statistical distribution from relations of creation, annihilation, and number operators. ► A systemic study on the statistical distributions corresponding to various q-deformation schemes. ► Arguing that many results of q-deformation distributions in literature are inaccurate or incomplete

Comparing exposure zones by different exposure metrics using statistical parameters: contrast and precision.

Science.gov (United States)

Park, Ji Young; Ramachandran, Gurumurthy; Raynor, Peter C; Eberly, Lynn E; Olson, Greg

2010-10-01

Recently, the appropriateness of using the 'mass concentration' metric for ultrafine particles has been questioned and surface area (SA) or number concentration metrics has been proposed as alternatives. To assess the abilities of various exposure metrics to distinguish between different exposure zones in workplaces with nanoparticle aerosols, exposure concentrations were measured in preassigned 'high-' and 'low-'exposure zones in a restaurant, an aluminum die-casting factory, and a diesel engine laboratory using SA, number, and mass concentration metrics. Predetermined exposure classifications were compared by each metric using statistical parameters and concentration ratios that were calculated from the different exposure concentrations. In the restaurant, SA and fine particle number concentrations showed significant differences between the high- and low-exposure zones and they had higher contrast (the ratio of between-zone variance to the sum of the between-zone and within-zone variances) than mass concentrations. Mass concentrations did not show significant differences. In the die cast facility, concentrations of all metrics were significantly greater in the high zone than in the low zone. SA and fine particle number concentrations showed larger concentration ratios between the high and low zones and higher contrast than mass concentrations. None of the metrics were significantly different between the high- and low-exposure zones in the diesel engine laboratory. The SA and fine particle number concentrations appeared to be better at differentiating exposure zones and finding the particle generation sources in workplaces generating nanoparticles. Because the choice of an exposure metric has significant implications for epidemiologic studies and industrial hygiene practice, a multimetric sampling approach is recommended for nanoparticle exposure assessment.

Teachers and Textbooks: On Statistical Definitions in Senior Secondary Mathematics

Science.gov (United States)

Dunn, Peter K.; Marshman, Margaret; McDougall, Robert; Wiegand, Aaron

2015-01-01

The new "Australian Senior Secondary Curriculum: Mathematics" contains more statistics than the existing Australian Curricula. This case study examines how a group of Queensland mathematics teachers define the word "statistics" and five statistical terms from the new curricula. These definitions are compared to those used in…

Comparing Kaolin and Pinolene to Improve Sustainable Grapevine Production during Drought.

Directory of Open Access Journals (Sweden)

Luca Brillante

Full Text Available Viticulture is widely practiced in dry regions, where the grapevine is greatly exposed to water stress. Optimizing plant water use efficiency (WUE without affecting crop yield, grape and wine quality is crucial to limiting use of water for irrigation and to significantly improving viticulture sustainability. This study examines the use in vineyards of particle film technology (engineered kaolin and compares it to a film-forming antitranspirant (pinolene, traditionally used to limit leaf water loss, and to an untreated control. The trial was carried out under field conditions over three growing seasons, during which moderate to very severe plant water stress (down to -1.9 MPa was measured through stem water potential. Leaf stomatal conductance (gs and photosynthesis rate (An were measured during the seasons and used to compute intrinsic WUE (WUEi, defined as An/gs ratio. Leaf temperature was also recorded and compared between treatments. Bunch quantity, bunch and berry weight, sugar accumulation, anthocyanin and flavonoid contents were measured. Finally, microvinifications were performed and resultant wines subjected to sensory evaluation.Results showed that the use of kaolin increased grapevine intrinsic WUE (+18% on average as compared to unsprayed vines without affecting berry and bunch weight and quantity, or sugar level. Anthocyanin content increased (+35% in kaolin treatment, and the wine was judged more attractive (p-value <0.05 and slightly more appreciated (p-value < 0.1 than control. Pinolene did not increase WUEi, limiting An more than gs; grapes with this treatment contained lower sugar and anthocyanin content than control, and the obtained wine was the least appreciated. This study demonstrates that particle film technology can improve vine WUEi and wine quality at the same time, while traditional antitranspirants were not as effective for these purposes. This positive effect can be used in interaction with other already

Statistical analysis of RHIC beam position monitors performance

Science.gov (United States)

Calaga, R.; Tomás, R.

2004-04-01

A detailed statistical analysis of beam position monitors (BPM) performance at RHIC is a critical factor in improving regular operations and future runs. Robust identification of malfunctioning BPMs plays an important role in any orbit or turn-by-turn analysis. Singular value decomposition and Fourier transform methods, which have evolved as powerful numerical techniques in signal processing, will aid in such identification from BPM data. This is the first attempt at RHIC to use a large set of data to statistically enhance the capability of these two techniques and determine BPM performance. A comparison from run 2003 data shows striking agreement between the two methods and hence can be used to improve BPM functioning at RHIC and possibly other accelerators.

Statistical analysis of RHIC beam position monitors performance

Directory of Open Access Journals (Sweden)

R. Calaga

2004-04-01

Full Text Available A detailed statistical analysis of beam position monitors (BPM performance at RHIC is a critical factor in improving regular operations and future runs. Robust identification of malfunctioning BPMs plays an important role in any orbit or turn-by-turn analysis. Singular value decomposition and Fourier transform methods, which have evolved as powerful numerical techniques in signal processing, will aid in such identification from BPM data. This is the first attempt at RHIC to use a large set of data to statistically enhance the capability of these two techniques and determine BPM performance. A comparison from run 2003 data shows striking agreement between the two methods and hence can be used to improve BPM functioning at RHIC and possibly other accelerators.

Intensive inpatient treatment for bulimia nervosa: Statistical and clinical significance of symptom changes.

Science.gov (United States)

Diedrich, Alice; Schlegl, Sandra; Greetfeld, Martin; Fumi, Markus; Voderholzer, Ulrich

2018-03-01

This study examines the statistical and clinical significance of symptom changes during an intensive inpatient treatment program with a strong psychotherapeutic focus for individuals with severe bulimia nervosa. 295 consecutively admitted bulimic patients were administered the Structured Interview for Anorexic and Bulimic Syndromes-Self-Rating (SIAB-S), the Eating Disorder Inventory-2 (EDI-2), the Brief Symptom Inventory (BSI), and the Beck Depression Inventory-II (BDI-II) at treatment intake and discharge. Results indicated statistically significant symptom reductions with large effect sizes regarding severity of binge eating and compensatory behavior (SIAB-S), overall eating disorder symptom severity (EDI-2), overall psychopathology (BSI), and depressive symptom severity (BDI-II) even when controlling for antidepressant medication. The majority of patients showed either reliable (EDI-2: 33.7%, BSI: 34.8%, BDI-II: 18.1%) or even clinically significant symptom changes (EDI-2: 43.2%, BSI: 33.9%, BDI-II: 56.9%). Patients with clinically significant improvement were less distressed at intake and less likely to suffer from a comorbid borderline personality disorder when compared with those who did not improve to a clinically significant extent. Findings indicate that intensive psychotherapeutic inpatient treatment may be effective in about 75% of severely affected bulimic patients. For the remaining non-responding patients, inpatient treatment might be improved through an even stronger focus on the reduction of comorbid borderline personality traits.

Improving participation rates by providing choice of participation mode: two randomized controlled trials

NARCIS (Netherlands)

Heijmans, N.; Lieshout, J. van; Wensing, M.J.

2015-01-01

BACKGROUND: Low participation rates reduce effective sample size, statistical power and can increase risk for selection bias. Previous research suggests that offering choice of participation mode can improve participation rates. However, few head-to-head trials compared choice of participation mode

A nonparametric spatial scan statistic for continuous data.

Science.gov (United States)

Jung, Inkyung; Cho, Ho Jin

2015-10-20

Spatial scan statistics are widely used for spatial cluster detection, and several parametric models exist. For continuous data, a normal-based scan statistic can be used. However, the performance of the model has not been fully evaluated for non-normal data. We propose a nonparametric spatial scan statistic based on the Wilcoxon rank-sum test statistic and compared the performance of the method with parametric models via a simulation study under various scenarios. The nonparametric method outperforms the normal-based scan statistic in terms of power and accuracy in almost all cases under consideration in the simulation study. The proposed nonparametric spatial scan statistic is therefore an excellent alternative to the normal model for continuous data and is especially useful for data following skewed or heavy-tailed distributions.

In vitro radiosensitivity of six human cell lines. A comparative study with different statistical models

International Nuclear Information System (INIS)

Fertil, B.; Deschavanne, P.J.; Lachet, B.; Malaise, E.P.

1980-01-01

The intrinsic radiosensitivity of human cell lines (five tumor and one nontransformed fibroblastic) was studied in vitro. The survival curves were fitted by the single-hit multitarget, the two-hit multitarget, the single-hit multitarget with initial slope, and the quadratic models. The accuracy of the experimental results permitted evaluation of the various fittings. Both a statistical test (comparison of variances left unexplained by the four models) and a biological consideration (check for independence of the fitted parameters vis-a-vis the portion of the survival curve in question) were carried out. The quadratic model came out best with each of them. It described the low-dose effects satisfactorily, revealing a single-hit lethal component. This finding and the fact that the six survival curves displayed a continuous curvature ruled out the adoption of the target models as well as the widely used linear regression. As calculated by the quadratic model, the parameters of the six cell lines lead to the following conclusions: (a) the intrinsic radiosensitivity varies greatly among the different cell lines; (b) the interpretation of the fibroblast survival curve is not basically different from that of the tumor cell lines; and (c) the radiosensitivity of these human cell lines is comparable to that of other mammalian cell lines

Comparative attitude and plans of the medical students and young Nepalese doctors.

Science.gov (United States)

Lakhey, M; Lakhey, S; Niraula, S R; Jha, D; Pant, R

2009-01-01

Many doctors are leaving Nepal to work abroad. To understand this problem better, we decided to study the attitude and plans of young doctors and medical students. This cross-sectional study was conducted at Kathmandu Medical College involving 65 first year medical students, 100 interns and 100 house officers. The data collected was entered in Microsoft excel and analysed by SPSS (Statistical Package for Social Sciences) programme. Chi-square test was used to compare two proportions. Significance level was set at 5%. Only 2% house officers said that their job prospects were excellent as compared to 22.4% of students, whereas 20% house officers as compared to 9% students thought job prospects in Nepal were poor (p= 0.003). Eighty two percent of students thought that a doctor's service to his country was very important as compared to 51% of interns (p= 0.001) and 58% of house officers. Forty percent of students, 58% of interns and 48% of house officers (no statistical significance between the three groups) planned to migrate to a developed country after graduation. Eighty eight percent of students, 89% interns and 74% of house officers (no statistical significant differences between the three groups) were of the opinion that improving career opportunities or working environment of the doctor could make the profession more attractive. Although majority of students, interns and house officers were of the opinion that a doctor's service to his community/country was very important, almost half of them still planned to migrate to a developed country after graduation. Improving the chances of professional advancement and professional working environment can make the profession more attractive, and therefore, may decrease this tendency for brain drain from our country.

Transportation Statistics Annual Report 1997

Energy Technology Data Exchange (ETDEWEB)

Fenn, M.

1997-01-01

This document is the fourth Transportation Statistics Annual Report (TSAR) prepared by the Bureau of Transportation Statistics (BTS) for the President and Congress. As in previous years, it reports on the state of U.S. transportation system at two levels. First, in Part I, it provides a statistical and interpretive survey of the system—its physical characteristics, its economic attributes, aspects of its use and performance, and the scale and severity of unintended consequences of transportation, such as fatalities and injuries, oil import dependency, and environment impacts. Part I also explores the state of transportation statistics, and new needs of the rapidly changing world of transportation. Second, Part II of the report, as in prior years, explores in detail the performance of the U.S. transportation system from the perspective of desired social outcomes or strategic goals. This year, the performance aspect of transportation chosen for thematic treatment is “Mobility and Access,” which complements past TSAR theme sections on “The Economic Performance of Transportation” (1995) and “Transportation and the Environment” (1996). Mobility and access are at the heart of the transportation system’s performance from the user’s perspective. In what ways and to what extent does the geographic freedom provided by transportation enhance personal fulfillment of the nation’s residents and contribute to economic advancement of people and businesses? This broad question underlies many of the topics examined in Part II: What is the current level of personal mobility in the United States, and how does it vary by sex, age, income level, urban or rural location, and over time? What factors explain variations? Has transportation helped improve people’s access to work, shopping, recreational facilities, and medical services, and in what ways and in what locations? How have barriers, such as age, disabilities, or lack of an automobile, affected these

Statistics

CERN Document Server

Hayslett, H T

1991-01-01

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

Does double-row rotator cuff repair improve functional outcome of patients compared with single-row technique? A systematic review.

Science.gov (United States)

DeHaan, Alexander M; Axelrad, Thomas W; Kaye, Elizabeth; Silvestri, Lorenzo; Puskas, Brian; Foster, Timothy E

2012-05-01

The advantage of single-row versus double-row arthroscopic rotator cuff repair techniques has been a controversial issue in sports medicine and shoulder surgery. There is biomechanical evidence that double-row techniques are superior to single-row techniques; however, there is no clinical evidence that the double-row technique provides an improved functional outcome. When compared with single-row rotator cuff repair, double-row fixation, although biomechanically superior, has no clinical benefit with respect to retear rate or improved functional outcome. Systematic review. The authors reviewed prospective studies of level I or II clinical evidence that compared the efficacy of single- and double-row rotator cuff repairs. Functional outcome scores included the American Shoulder and Elbow Surgeons (ASES) shoulder scale, the Constant shoulder score, and the University of California, Los Angeles (UCLA) shoulder rating scale. Radiographic failures and complications were also analyzed. A test of heterogeneity for patient demographics was also performed to determine if there were differences in the patient profiles across the included studies. Seven studies fulfilled our inclusion criteria. The test of heterogeneity across these studies showed no differences. The functional ASES, Constant, and UCLA outcome scores revealed no difference between single- and double-row rotator cuff repairs. The total retear rate, which included both complete and partial retears, was 43.1% for the single-row repair and 27.2% for the double-row repair (P = .057), representing a trend toward higher failures in the single-row group. Through a comprehensive literature search and meta-analysis of current arthroscopic rotator cuff repairs, we found that the single-row repairs did not differ from the double-row repairs in functional outcome scores. The double-row repairs revealed a trend toward a lower radiographic proven retear rate, although the data did not reach statistical significance. There

Comparing emerging and mature markets during times of crises: A non-extensive statistical approach

Science.gov (United States)

Namaki, A.; Koohi Lai, Z.; Jafari, G. R.; Raei, R.; Tehrani, R.

2013-07-01

One of the important issues in finance and economics for both scholars and practitioners is to describe the behavior of markets, especially during times of crises. In this paper, we analyze the behavior of some mature and emerging markets with a Tsallis entropy framework that is a non-extensive statistical approach based on non-linear dynamics. During the past decade, this technique has been successfully applied to a considerable number of complex systems such as stock markets in order to describe the non-Gaussian behavior of these systems. In this approach, there is a parameter q, which is a measure of deviation from Gaussianity, that has proved to be a good index for detecting crises. We investigate the behavior of this parameter in different time scales for the market indices. It could be seen that the specified pattern for q differs for mature markets with regard to emerging markets. The findings show the robustness of the stated approach in order to follow the market conditions over time. It is obvious that, in times of crises, q is much greater than in other times. In addition, the response of emerging markets to global events is delayed compared to that of mature markets, and tends to a Gaussian profile on increasing the scale. This approach could be very useful in application to risk and portfolio management in order to detect crises by following the parameter q in different time scales.

Statistical lamb wave localization based on extreme value theory

Science.gov (United States)

Harley, Joel B.

2018-04-01

Guided wave localization methods based on delay-and-sum imaging, matched field processing, and other techniques have been designed and researched to create images that locate and describe structural damage. The maximum value of these images typically represent an estimated damage location. Yet, it is often unclear if this maximum value, or any other value in the image, is a statistically significant indicator of damage. Furthermore, there are currently few, if any, approaches to assess the statistical significance of guided wave localization images. As a result, we present statistical delay-and-sum and statistical matched field processing localization methods to create statistically significant images of damage. Our framework uses constant rate of false alarm statistics and extreme value theory to detect damage with little prior information. We demonstrate our methods with in situ guided wave data from an aluminum plate to detect two 0.75 cm diameter holes. Our results show an expected improvement in statistical significance as the number of sensors increase. With seventeen sensors, both methods successfully detect damage with statistical significance.

CYberinfrastructure for COmparative effectiveness REsearch (CYCORE): improving data from cancer clinical trials.

Science.gov (United States)

Patrick, Kevin; Wolszon, Laura; Basen-Engquist, Karen M; Demark-Wahnefried, Wendy; Prokhorov, Alex V; Barrera, Stephanie; Baru, Chaitan; Farcas, Emilia; Krueger, Ingolf; Palmer, Doug; Raab, Fred; Rios, Phil; Ziftci, Celal; Peterson, Susan

2011-03-01

Improved approaches and methodologies are needed to conduct comparative effectiveness research (CER) in oncology. While cancer therapies continue to emerge at a rapid pace, the review, synthesis, and dissemination of evidence-based interventions across clinical trials lag in comparison. Rigorous and systematic testing of competing therapies has been clouded by age-old problems: poor patient adherence, inability to objectively measure the environmental influences on health, lack of knowledge about patients' lifestyle behaviors that may affect cancer's progression and recurrence, and limited ability to compile and interpret the wide range of variables that must be considered in the cancer treatment. This lack of data integration limits the potential for patients and clinicians to engage in fully informed decision-making regarding cancer prevention, treatment, and survivorship care, and the translation of research results into mainstream medical care. Particularly important, as noted in a 2009 report on CER to the President and Congress, the limited focus on health behavior-change interventions was a major hindrance in this research landscape (DHHS 2009). This paper describes an initiative to improve CER for cancer by addressing several of these limitations. The Cyberinfrastructure for Comparative Effectiveness Research (CYCORE) project, informed by the National Science Foundation's 2007 report "Cyberinfrastructure Vision for 21(st) Century Discovery" has, as its central aim, the creation of a prototype for a user-friendly, open-source cyberinfrastructure (CI) that supports acquisition, storage, visualization, analysis, and sharing of data important for cancer-related CER. Although still under development, the process of gathering requirements for CYCORE has revealed new ways in which CI design can significantly improve the collection and analysis of a wide variety of data types, and has resulted in new and important partnerships among cancer researchers engaged in

Statistics and analysis of scientific data

CERN Document Server

Bonamente, Massimiliano

2017-01-01

The revised second edition of this textbook provides the reader with a solid foundation in probability theory and statistics as applied to the physical sciences, engineering and related fields. It covers a broad range of numerical and analytical methods that are essential for the correct analysis of scientific data, including probability theory, distribution functions of statistics, fits to two-dimensional data and parameter estimation, Monte Carlo methods and Markov chains. Features new to this edition include: • a discussion of statistical techniques employed in business science, such as multiple regression analysis of multivariate datasets. • a new chapter on the various measures of the mean including logarithmic averages. • new chapters on systematic errors and intrinsic scatter, and on the fitting of data with bivariate errors. • a new case study and additional worked examples. • mathematical derivations and theoretical background material have been appropriately marked,to improve the readabili...

Statistical and extra-statistical considerations in differential item functioning analyses

Directory of Open Access Journals (Sweden)

G. K. Huysamen

2004-10-01

Full Text Available This article briefly describes the main procedures for performing differential item functioning (DIF analyses and points out some of the statistical and extra-statistical implications of these methods. Research findings on the sources of DIF, including those associated with translated tests, are reviewed. As DIF analyses are oblivious of correlations between a test and relevant criteria, the elimination of differentially functioning items does not necessarily improve predictive validity or reduce any predictive bias. The implications of the results of past DIF research for test development in the multilingual and multi-cultural South African society are considered. Opsomming Hierdie artikel beskryf kortliks die hoofprosedures vir die ontleding van differensiële itemfunksionering (DIF en verwys na sommige van die statistiese en buite-statistiese implikasies van hierdie metodes. ’n Oorsig word verskaf van navorsingsbevindings oor die bronne van DIF, insluitend dié by vertaalde toetse. Omdat DIF-ontledings nie die korrelasies tussen ’n toets en relevante kriteria in ag neem nie, sal die verwydering van differensieel-funksionerende items nie noodwendig voorspellingsgeldigheid verbeter of voorspellingsydigheid verminder nie. Die implikasies van vorige DIF-navorsingsbevindings vir toetsontwikkeling in die veeltalige en multikulturele Suid-Afrikaanse gemeenskap word oorweeg.

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

Science.gov (United States)

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

2018-03-01

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

Intensity-Modulated Radiotherapy for Sinonasal Cancer: Improved Outcome Compared to Conventional Radiotherapy

International Nuclear Information System (INIS)

Dirix, Piet; Vanstraelen, Bianca; Jorissen, Mark; Vander Poorten, Vincent; Nuyts, Sandra

2010-01-01

Purpose: To evaluate clinical outcome and toxicity of postoperative intensity-modulated radiotherapy (IMRT) for malignancies of the nasal cavity and paranasal sinuses. Methods and Materials: Between 2003 and 2008, 40 patients with cancer of the paranasal sinuses (n = 34) or nasal cavity (n = 6) received postoperative IMRT to a dose of 60 Gy (n = 21) or 66 Gy (n = 19). Treatment outcome and toxicity were retrospectively compared with that of a previous patient group (n = 41) who were also postoperatively treated to the same doses but with three-dimensional conformal radiotherapy without intensity modulation, from 1992 to 2002. Results: Median follow-up was 30 months (range, 4-74 months). Two-year local control, overall survival, and disease-free survival were 76%, 89%, and 72%, respectively. Compared to the three-dimensional conformal radiotherapy treatment, IMRT resulted in significantly improved disease-free survival (60% vs. 72%; p = 0.02). No grade 3 or 4 toxicity was reported in the IMRT group, either acute or chronic. The use of IMRT significantly reduced the incidence of acute as well as late side effects, especially regarding skin toxicity, mucositis, xerostomia, and dry-eye syndrome. Conclusions: Postoperative IMRT for sinonasal cancer significantly improves disease-free survival and reduces acute as well as late toxicity. Consequently, IMRT should be considered the standard treatment modality for malignancies of the nasal cavity and paranasal sinuses.

Direct integration of intensity-level data from Affymetrix and Illumina microarrays improves statistical power for robust reanalysis

Directory of Open Access Journals (Sweden)

Turnbull Arran K

2012-08-01

Full Text Available Abstract Background Affymetrix GeneChips and Illumina BeadArrays are the most widely used commercial single channel gene expression microarrays. Public data repositories are an extremely valuable resource, providing array-derived gene expression measurements from many thousands of experiments. Unfortunately many of these studies are underpowered and it is desirable to improve power by combining data from more than one study; we sought to determine whether platform-specific bias precludes direct integration of probe intensity signals for combined reanalysis. Results Using Affymetrix and Illumina data from the microarray quality control project, from our own clinical samples, and from additional publicly available datasets we evaluated several approaches to directly integrate intensity level expression data from the two platforms. After mapping probe sequences to Ensembl genes we demonstrate that, ComBat and cross platform normalisation (XPN, significantly outperform mean-centering and distance-weighted discrimination (DWD in terms of minimising inter-platform variance. In particular we observed that DWD, a popular method used in a number of previous studies, removed systematic bias at the expense of genuine biological variability, potentially reducing legitimate biological differences from integrated datasets. Conclusion Normalised and batch-corrected intensity-level data from Affymetrix and Illumina microarrays can be directly combined to generate biologically meaningful results with improved statistical power for robust, integrated reanalysis.

Is it safe to use Poisson statistics in nuclear spectrometry?

International Nuclear Information System (INIS)

Pomme, S.; Robouch, P.; Arana, G.; Eguskiza, M.; Maguregui, M.I.

2000-01-01

The boundary conditions in which Poisson statistics can be applied in nuclear spectrometry are investigated. Improved formulas for the uncertainty of nuclear counting with deadtime and pulse pileup are presented. A comparison is made between the expected statistical uncertainty for loss-free counting, fixed live-time and fixed real-time measurements. (author)

Energy statistics France; Statistiques energetiques France

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-04-01

This document presents statistical data on energy accounting in France compared to other european countries. Many tables and charts on energy consumption, energy invoice and prices are provided by sectors. (A.L.B.)

Diffeomorphic Statistical Deformation Models

DEFF Research Database (Denmark)

Hansen, Michael Sass; Hansen, Mads/Fogtman; Larsen, Rasmus

2007-01-01

In this paper we present a new method for constructing diffeomorphic statistical deformation models in arbitrary dimensional images with a nonlinear generative model and a linear parameter space. Our deformation model is a modified version of the diffeomorphic model introduced by Cootes et al....... The modifications ensure that no boundary restriction has to be enforced on the parameter space to prevent folds or tears in the deformation field. For straightforward statistical analysis, principal component analysis and sparse methods, we assume that the parameters for a class of deformations lie on a linear...... with ground truth in form of manual expert annotations, and compared to Cootes's model. We anticipate applications in unconstrained diffeomorphic synthesis of images, e.g. for tracking, segmentation, registration or classification purposes....

The role of ensemble-based statistics in variational assimilation of cloud-affected observations from infrared imagers

Science.gov (United States)

Hacker, Joshua; Vandenberghe, Francois; Jung, Byoung-Jo; Snyder, Chris

2017-04-01

Effective assimilation of cloud-affected radiance observations from space-borne imagers, with the aim of improving cloud analysis and forecasting, has proven to be difficult. Large observation biases, nonlinear observation operators, and non-Gaussian innovation statistics present many challenges. Ensemble-variational data assimilation (EnVar) systems offer the benefits of flow-dependent background error statistics from an ensemble, and the ability of variational minimization to handle nonlinearity. The specific benefits of ensemble statistics, relative to static background errors more commonly used in variational systems, have not been quantified for the problem of assimilating cloudy radiances. A simple experiment framework is constructed with a regional NWP model and operational variational data assimilation system, to provide the basis understanding the importance of ensemble statistics in cloudy radiance assimilation. Restricting the observations to those corresponding to clouds in the background forecast leads to innovations that are more Gaussian. The number of large innovations is reduced compared to the more general case of all observations, but not eliminated. The Huber norm is investigated to handle the fat tails of the distributions, and allow more observations to be assimilated without the need for strict background checks that eliminate them. Comparing assimilation using only ensemble background error statistics with assimilation using only static background error statistics elucidates the importance of the ensemble statistics. Although the cost functions in both experiments converge to similar values after sufficient outer-loop iterations, the resulting cloud water, ice, and snow content are greater in the ensemble-based analysis. The subsequent forecasts from the ensemble-based analysis also retain more condensed water species, indicating that the local environment is more supportive of clouds. In this presentation we provide details that explain the

Industrial commodity statistics yearbook 2001. Production statistics (1992-2001)

International Nuclear Information System (INIS)

2003-01-01

This is the thirty-fifth in a series of annual compilations of statistics on world industry designed to meet both the general demand for information of this kind and the special requirements of the United Nations and related international bodies. Beginning with the 1992 edition, the title of the publication was changed to industrial Commodity Statistics Yearbook as the result of a decision made by the United Nations Statistical Commission at its twenty-seventh session to discontinue, effective 1994, publication of the Industrial Statistics Yearbook, volume I, General Industrial Statistics by the Statistics Division of the United Nations. The United Nations Industrial Development Organization (UNIDO) has become responsible for the collection and dissemination of general industrial statistics while the Statistics Division of the United Nations continues to be responsible for industrial commodity production statistics. The previous title, Industrial Statistics Yearbook, volume II, Commodity Production Statistics, was introduced in the 1982 edition. The first seven editions in this series were published under the title The Growth of World industry and the next eight editions under the title Yearbook of Industrial Statistics. This edition of the Yearbook contains annual quantity data on production of industrial commodities by country, geographical region, economic grouping and for the world. A standard list of about 530 commodities (about 590 statistical series) has been adopted for the publication. The statistics refer to the ten-year period 1992-2001 for about 200 countries and areas

Industrial commodity statistics yearbook 2002. Production statistics (1993-2002)

International Nuclear Information System (INIS)

2004-01-01

This is the thirty-sixth in a series of annual compilations of statistics on world industry designed to meet both the general demand for information of this kind and the special requirements of the United Nations and related international bodies. Beginning with the 1992 edition, the title of the publication was changed to industrial Commodity Statistics Yearbook as the result of a decision made by the United Nations Statistical Commission at its twenty-seventh session to discontinue, effective 1994, publication of the Industrial Statistics Yearbook, volume I, General Industrial Statistics by the Statistics Division of the United Nations. The United Nations Industrial Development Organization (UNIDO) has become responsible for the collection and dissemination of general industrial statistics while the Statistics Division of the United Nations continues to be responsible for industrial commodity production statistics. The previous title, Industrial Statistics Yearbook, volume II, Commodity Production Statistics, was introduced in the 1982 edition. The first seven editions in this series were published under the title 'The Growth of World industry' and the next eight editions under the title 'Yearbook of Industrial Statistics'. This edition of the Yearbook contains annual quantity data on production of industrial commodities by country, geographical region, economic grouping and for the world. A standard list of about 530 commodities (about 590 statistical series) has been adopted for the publication. The statistics refer to the ten-year period 1993-2002 for about 200 countries and areas

Industrial commodity statistics yearbook 2000. Production statistics (1991-2000)

International Nuclear Information System (INIS)

2002-01-01

This is the thirty-third in a series of annual compilations of statistics on world industry designed to meet both the general demand for information of this kind and the special requirements of the United Nations and related international bodies. Beginning with the 1992 edition, the title of the publication was changed to industrial Commodity Statistics Yearbook as the result of a decision made by the United Nations Statistical Commission at its twenty-seventh session to discontinue, effective 1994, publication of the Industrial Statistics Yearbook, volume I, General Industrial Statistics by the Statistics Division of the United Nations. The United Nations Industrial Development Organization (UNIDO) has become responsible for the collection and dissemination of general industrial statistics while the Statistics Division of the United Nations continues to be responsible for industrial commodity production statistics. The previous title, Industrial Statistics Yearbook, volume II, Commodity Production Statistics, was introduced in the 1982 edition. The first seven editions in this series were published under the title The Growth of World industry and the next eight editions under the title Yearbook of Industrial Statistics. This edition of the Yearbook contains annual quantity data on production of industrial commodities by country, geographical region, economic grouping and for the world. A standard list of about 530 commodities (about 590 statistical series) has been adopted for the publication. Most of the statistics refer to the ten-year period 1991-2000 for about 200 countries and areas

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

Science.gov (United States)

Satorra, Albert; Bentler, Peter M

2010-06-01

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

Enhancing pediatric clinical trial feasibility through the use of Bayesian statistics.

Science.gov (United States)

Huff, Robin A; Maca, Jeff D; Puri, Mala; Seltzer, Earl W

2017-11-01

BackgroundPediatric clinical trials commonly experience recruitment challenges including limited number of patients and investigators, inclusion/exclusion criteria that further reduce the patient pool, and a competitive research landscape created by pediatric regulatory commitments. To overcome these challenges, innovative approaches are needed.MethodsThis article explores the use of Bayesian statistics to improve pediatric trial feasibility, using pediatric Type-2 diabetes as an example. Data for six therapies approved for adults were used to perform simulations to determine the impact on pediatric trial size.ResultsWhen the number of adult patients contributing to the simulation was assumed to be the same as the number of patients to be enrolled in the pediatric trial, the pediatric trial size was reduced by 75-78% when compared with a frequentist statistical approach, but was associated with a 34-45% false-positive rate. In subsequent simulations, greater control was exerted over the false-positive rate by decreasing the contribution of the adult data. A 30-33% reduction in trial size was achieved when false-positives were held to less than 10%.ConclusionReducing the trial size through the use of Bayesian statistics would facilitate completion of pediatric trials, enabling drugs to be labeled appropriately for children.

Which statistics should tropical biologists learn?

Science.gov (United States)

Loaiza Velásquez, Natalia; González Lutz, María Isabel; Monge-Nájera, Julián

2011-09-01

Tropical biologists study the richest and most endangered biodiversity in the planet, and in these times of climate change and mega-extinctions, the need for efficient, good quality research is more pressing than in the past. However, the statistical component in research published by tropical authors sometimes suffers from poor quality in data collection; mediocre or bad experimental design and a rigid and outdated view of data analysis. To suggest improvements in their statistical education, we listed all the statistical tests and other quantitative analyses used in two leading tropical journals, the Revista de Biología Tropical and Biotropica, during a year. The 12 most frequent tests in the articles were: Analysis of Variance (ANOVA), Chi-Square Test, Student's T Test, Linear Regression, Pearson's Correlation Coefficient, Mann-Whitney U Test, Kruskal-Wallis Test, Shannon's Diversity Index, Tukey's Test, Cluster Analysis, Spearman's Rank Correlation Test and Principal Component Analysis. We conclude that statistical education for tropical biologists must abandon the old syllabus based on the mathematical side of statistics and concentrate on the correct selection of these and other procedures and tests, on their biological interpretation and on the use of reliable and friendly freeware. We think that their time will be better spent understanding and protecting tropical ecosystems than trying to learn the mathematical foundations of statistics: in most cases, a well designed one-semester course should be enough for their basic requirements.

Statistical Estimators Using Jointly Administrative and Survey Data to Produce French Structural Business Statistics

Directory of Open Access Journals (Sweden)

Brion Philippe

2015-12-01

Full Text Available Using as much administrative data as possible is a general trend among most national statistical institutes. Different kinds of administrative sources, from tax authorities or other administrative bodies, are very helpful material in the production of business statistics. However, these sources often have to be completed by information collected through statistical surveys. This article describes the way Insee has implemented such a strategy in order to produce French structural business statistics. The originality of the French procedure is that administrative and survey variables are used jointly for the same enterprises, unlike the majority of multisource systems, in which the two kinds of sources generally complement each other for different categories of units. The idea is to use, as much as possible, the richness of the administrative sources combined with the timeliness of a survey, even if the latter is conducted only on a sample of enterprises. One main issue is the classification of enterprises within the NACE nomenclature, which is a cornerstone variable in producing the breakdown of the results by industry. At a given date, two values of the corresponding code may coexist: the value of the register, not necessarily up to date, and the value resulting from the data collected via the survey, but only from a sample of enterprises. Using all this information together requires the implementation of specific statistical estimators combining some properties of the difference estimators with calibration techniques. This article presents these estimators, as well as their statistical properties, and compares them with those of other methods.

Evolution of the Field of Statistics at Los Alamos

Energy Technology Data Exchange (ETDEWEB)

Picard, Richard Roy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-05-24

Through years of technological improvements, cultural change, advances in statistical theory, revisions of federal government structure and policies, Laboratory re-organizations, offce re-locations, and so on, the practice of statistics at Los Alamos has evolved from its origins in the early 1950s, with a handful of statisticians working in LASL group T-1, to present-day group CCS-6. This report chronicles that history.

Do doctors need statistics? Doctors' use of and attitudes to probability and statistics.

Science.gov (United States)

Swift, Louise; Miles, Susan; Price, Gill M; Shepstone, Lee; Leinster, Sam J

2009-07-10

There is little published evidence on what doctors do in their work that requires probability and statistics, yet the General Medical Council (GMC) requires new doctors to have these skills. This study investigated doctors' use of and attitudes to probability and statistics with a view to informing undergraduate teaching.An email questionnaire was sent to 473 clinicians with an affiliation to the University of East Anglia's Medical School.Of 130 respondents approximately 90 per cent of doctors who performed each of the following activities found probability and statistics useful for that activity: accessing clinical guidelines and evidence summaries, explaining levels of risk to patients, assessing medical marketing and advertising material, interpreting the results of a screening test, reading research publications for general professional interest, and using research publications to explore non-standard treatment and management options.Seventy-nine per cent (103/130, 95 per cent CI 71 per cent, 86 per cent) of participants considered probability and statistics important in their work. Sixty-three per cent (78/124, 95 per cent CI 54 per cent, 71 per cent) said that there were activities that they could do better or start doing if they had an improved understanding of these areas and 74 of these participants elaborated on this. Themes highlighted by participants included: being better able to critically evaluate other people's research; becoming more research-active, having a better understanding of risk; and being better able to explain things to, or teach, other people.Our results can be used to inform how probability and statistics should be taught to medical undergraduates and should encourage today's medical students of the subjects' relevance to their future careers. Copyright 2009 John Wiley & Sons, Ltd.

China's energy statistics in a global context: A methodology to develop regional energy balances for East, Central and West China

DEFF Research Database (Denmark)

Mischke, Peggy

2013-01-01

for research and policy analysis. An improved understanding of the quality and reliability of Chinese economic and energy data is becoming more important to to understanding global energy markets and future greenhouse gas emissions. China’s national statistical system to track such changes is however still...... developing and, in some instances, energy data remain unavailable in the public domain. This working paper discusses China’s energy and economic statistics in view of identifying suitable indicators to develop a simplified regional energy systems for China from a variety of publicly available data. As China......’s national statistical system continuous to be debated and criticised in terms of data quality, comparability and reliability, an overview of the milestones, status and main issues of China’s energy statistics is given. In a next step, the energy balance format of the International Energy Agency is used...

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

Science.gov (United States)

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

2006-10-01

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

Statistical implications in Monte Carlo depletions - 051

International Nuclear Information System (INIS)

Zhiwen, Xu; Rhodes, J.; Smith, K.

2010-01-01

As a result of steady advances of computer power, continuous-energy Monte Carlo depletion analysis is attracting considerable attention for reactor burnup calculations. The typical Monte Carlo analysis is set up as a combination of a Monte Carlo neutron transport solver and a fuel burnup solver. Note that the burnup solver is a deterministic module. The statistical errors in Monte Carlo solutions are introduced into nuclide number densities and propagated along fuel burnup. This paper is towards the understanding of the statistical implications in Monte Carlo depletions, including both statistical bias and statistical variations in depleted fuel number densities. The deterministic Studsvik lattice physics code, CASMO-5, is modified to model the Monte Carlo depletion. The statistical bias in depleted number densities is found to be negligible compared to its statistical variations, which, in turn, demonstrates the correctness of the Monte Carlo depletion method. Meanwhile, the statistical variation in number densities generally increases with burnup. Several possible ways of reducing the statistical errors are discussed: 1) to increase the number of individual Monte Carlo histories; 2) to increase the number of time steps; 3) to run additional independent Monte Carlo depletion cases. Finally, a new Monte Carlo depletion methodology, called the batch depletion method, is proposed, which consists of performing a set of independent Monte Carlo depletions and is thus capable of estimating the overall statistical errors including both the local statistical error and the propagated statistical error. (authors)

Statistical yearbook 2001. Data available as of 15 December 2003. 48 ed

International Nuclear Information System (INIS)

2004-01-01

This is the forty-eight issue of the United Nations Statistical Yearbook, prepared by the Statistics Division, Department of Economic and Social Affairs of the United Nations Secretariat. It contains series covering, in general, 1990-1999 or 1991-2000, based on statistics available to the Statistics Division up to 15 December 2003. The major purpose of the Statistical Yearbook is to provide in a single volume a comprehensive compilation of internationally available statistics on social and economic conditions and activities, at world, regional and national levels, covering roughly a ten-year period. Most of the statistics presented in the Yearbook are extracted from more detailed, specialized publications prepared by the Statistics Division and by many other international statistical services. Thus, while the specialized publications concentrate on monitoring topics and trends in particular social and economic fields, the Statistical Yearbook tables provide data for a more comprehensive, overall description of social and economic structures, conditions, changes and activities. The objective has been to collect, systematize and coordinate the most essential components of comparable statistical information which can give a broad and, to the extent feasible, a consistent picture of social and economic processes at world, regional and national levels. More specifically, the Statistical Yearbook provides systematic information on a wide range of social and economic issues which are of concern in the United Nations system and among the governments and peoples of the world. A particular value of the Yearbook, but also its greatest challenge, is that these issues are extensively interrelated. Meaningful analysis of these issues requires systematization and coordination of the data across many fields. These issues include: General economic growth and related economic conditions; economic situation in developing countries and progress towards the objectives adopted for the

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

Directory of Open Access Journals (Sweden)

Lee Anna Y

2009-02-01

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

Statistical analysis of the Ft. Calhoun reactor coolant pump system

International Nuclear Information System (INIS)

Heising, Carolyn D.

1998-01-01

In engineering science, statistical quality control techniques have traditionally been applied to control manufacturing processes. An application to commercial nuclear power plant maintenance and control is presented that can greatly improve plant safety. As a demonstration of such an approach to plant maintenance and control, a specific system is analyzed: the reactor coolant pumps (RCPs) of the Ft. Calhoun nuclear power plant. This research uses capability analysis, Shewhart X-bar, R-charts, canonical correlation methods, and design of experiments to analyze the process for the state of statistical control. The results obtained show that six out of ten parameters are under control specifications limits and four parameters are not in the state of statistical control. The analysis shows that statistical process control methods can be applied as an early warning system capable of identifying significant equipment problems well in advance of traditional control room alarm indicators Such a system would provide operators with ample time to respond to possible emergency situations and thus improve plant safety and reliability. (author)

Statistical perspectives on inverse problems

DEFF Research Database (Denmark)

Andersen, Kim Emil

of the interior of an object from electrical boundary measurements. One part of this thesis concerns statistical approaches for solving, possibly non-linear, inverse problems. Thus inverse problems are recasted in a form suitable for statistical inference. In particular, a Bayesian approach for regularisation...... problem is given in terms of probability distributions. Posterior inference is obtained by Markov chain Monte Carlo methods and new, powerful simulation techniques based on e.g. coupled Markov chains and simulated tempering is developed to improve the computational efficiency of the overall simulation......Inverse problems arise in many scientific disciplines and pertain to situations where inference is to be made about a particular phenomenon from indirect measurements. A typical example, arising in diffusion tomography, is the inverse boundary value problem for non-invasive reconstruction...

Gridded Calibration of Ensemble Wind Vector Forecasts Using Ensemble Model Output Statistics

Science.gov (United States)

Lazarus, S. M.; Holman, B. P.; Splitt, M. E.

2017-12-01

A computationally efficient method is developed that performs gridded post processing of ensemble wind vector forecasts. An expansive set of idealized WRF model simulations are generated to provide physically consistent high resolution winds over a coastal domain characterized by an intricate land / water mask. Ensemble model output statistics (EMOS) is used to calibrate the ensemble wind vector forecasts at observation locations. The local EMOS predictive parameters (mean and variance) are then spread throughout the grid utilizing flow-dependent statistical relationships extracted from the downscaled WRF winds. Using data withdrawal and 28 east central Florida stations, the method is applied to one year of 24 h wind forecasts from the Global Ensemble Forecast System (GEFS). Compared to the raw GEFS, the approach improves both the deterministic and probabilistic forecast skill. Analysis of multivariate rank histograms indicate the post processed forecasts are calibrated. Two downscaling case studies are presented, a quiescent easterly flow event and a frontal passage. Strengths and weaknesses of the approach are presented and discussed.

State of Business Statistics Education in MENA Region: A Comparative Study with Best Practices

Science.gov (United States)

Hijazi, Rafiq; Zoubeidi, Taoufik

2017-01-01

Purpose: The purpose of this study is to investigate the state of undergraduate business statistics education in the Middle East and North Africa (MENA) and assess its alignment with the best practices in equipping business graduates with the knowledge and skills demanded by the labor market. Design/methodology/approach: A survey of 108…

An Unsupervised Method of Change Detection in Multi-Temporal PolSAR Data Using a Test Statistic and an Improved K&I Algorithm

Directory of Open Access Journals (Sweden)

Jinqi Zhao

2017-12-01

Full Text Available In recent years, multi-temporal imagery from spaceborne sensors has provided a fast and practical means for surveying and assessing changes in terrain surfaces. Owing to the all-weather imaging capability, polarimetric synthetic aperture radar (PolSAR has become a key tool for change detection. Change detection methods include both unsupervised and supervised methods. Supervised change detection, which needs some human intervention, is generally ineffective and impractical. Due to this limitation, unsupervised methods are widely used in change detection. The traditional unsupervised methods only use a part of the polarization information, and the required thresholding algorithms are independent of the multi-temporal data, which results in the change detection map being ineffective and inaccurate. To solve these problems, a novel method of change detection using a test statistic based on the likelihood ratio test and the improved Kittler and Illingworth (K&I minimum-error thresholding algorithm is introduced in this paper. The test statistic is used to generate the comparison image (CI of the multi-temporal PolSAR images, and improved K&I using a generalized Gaussian model simulates the distribution of the CI. As a result of these advantages, we can obtain the change detection map using an optimum threshold. The efficiency of the proposed method is demonstrated by the use of multi-temporal PolSAR images acquired by RADARSAT-2 over Wuhan, China. The experimental results show that the proposed method is effective and highly accurate.

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

Science.gov (United States)

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

2016-01-01

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

Statistical process control for serially correlated data

NARCIS (Netherlands)

Wieringa, Jakob Edo

1999-01-01

Statistical Process Control (SPC) aims at quality improvement through reduction of variation. The best known tool of SPC is the control chart. Over the years, the control chart has proved to be a successful practical technique for monitoring process measurements. However, its usefulness in practice

Equivalent statistics and data interpretation.

Science.gov (United States)

Francis, Gregory

2017-08-01

Recent reform efforts in psychological science have led to a plethora of choices for scientists to analyze their data. A scientist making an inference about their data must now decide whether to report a p value, summarize the data with a standardized effect size and its confidence interval, report a Bayes Factor, or use other model comparison methods. To make good choices among these options, it is necessary for researchers to understand the characteristics of the various statistics used by the different analysis frameworks. Toward that end, this paper makes two contributions. First, it shows that for the case of a two-sample t test with known sample sizes, many different summary statistics are mathematically equivalent in the sense that they are based on the very same information in the data set. When the sample sizes are known, the p value provides as much information about a data set as the confidence interval of Cohen's d or a JZS Bayes factor. Second, this equivalence means that different analysis methods differ only in their interpretation of the empirical data. At first glance, it might seem that mathematical equivalence of the statistics suggests that it does not matter much which statistic is reported, but the opposite is true because the appropriateness of a reported statistic is relative to the inference it promotes. Accordingly, scientists should choose an analysis method appropriate for their scientific investigation. A direct comparison of the different inferential frameworks provides some guidance for scientists to make good choices and improve scientific practice.

Does patella lowering improve crouch gait in cerebral palsy? Comparative retrospective study.

Science.gov (United States)

Desailly, E; Thévenin-Lemoine, C; Khouri, N

2017-09-01

Patella lowering aims to improve quadriceps function as a means of correcting crouch gait in patients with cerebral palsy. Few studies have assessed the effects of patella lowering as a component of multilevel surgery. Including patella lowering into the components of multilevel surgery is beneficial in patients with crouch gait and patella alta. In 12 lower limbs with patella alta (Caton-Deschamps index>1.4) in 41 children with cerebral palsy, patella lowering was performed, without distal femoral extension osteotomy or hamstring release. Among limbs with similar surgical procedures (e.g., hamstring lengthening, rectus femoris transfer) except for patella lowering, controls were selected retrospectively by matching on a propensity score for patella lowering. The propensity score was computed based on preoperative knee flexion contracture, knee extension lag, and minimum knee flexion at mid-stance. Clinical and 3D kinematic data were compared between the two groups. The improvement in minimum knee flexion at mid-stance was significantly greater in the group with patellar lowering (-24°±12°vs. -12°±7°). The Gait Deviation Index improved similarly in the two groups. Knee flexion contracture improved only in the group with patellar lowering. Extension lag did not improve in either group. Peak knee flexion during the swing phase remained unchanged in both groups. Patellar lowering is effective in diminishing minimum knee flexion at mid-stance in patients with patella alta and crouch gait due to cerebral palsy. Patellar lowering has not adverse effects on gait. These findings cannot be assumed to apply to patients with normal patellar height. IV (retrospective study). Copyright © 2017. Published by Elsevier Masson SAS.

Statistical Compression for Climate Model Output

Science.gov (United States)

Hammerling, D.; Guinness, J.; Soh, Y. J.

2017-12-01

Numerical climate model simulations run at high spatial and temporal resolutions generate massive quantities of data. As our computing capabilities continue to increase, storing all of the data is not sustainable, and thus is it important to develop methods for representing the full datasets by smaller compressed versions. We propose a statistical compression and decompression algorithm based on storing a set of summary statistics as well as a statistical model describing the conditional distribution of the full dataset given the summary statistics. We decompress the data by computing conditional expectations and conditional simulations from the model given the summary statistics. Conditional expectations represent our best estimate of the original data but are subject to oversmoothing in space and time. Conditional simulations introduce realistic small-scale noise so that the decompressed fields are neither too smooth nor too rough compared with the original data. Considerable attention is paid to accurately modeling the original dataset-one year of daily mean temperature data-particularly with regard to the inherent spatial nonstationarity in global fields, and to determining the statistics to be stored, so that the variation in the original data can be closely captured, while allowing for fast decompression and conditional emulation on modest computers.

Harmonic statistics

International Nuclear Information System (INIS)

Eliazar, Iddo

2017-01-01

The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.

Harmonic statistics

Energy Technology Data Exchange (ETDEWEB)

Eliazar, Iddo, E-mail: eliazar@post.tau.ac.il

2017-05-15

The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.

Heuristic versus statistical physics approach to optimization problems

International Nuclear Information System (INIS)

Jedrzejek, C.; Cieplinski, L.

1995-01-01

Optimization is a crucial ingredient of many calculation schemes in science and engineering. In this paper we assess several classes of methods: heuristic algorithms, methods directly relying on statistical physics such as the mean-field method and simulated annealing; and Hopfield-type neural networks and genetic algorithms partly related to statistical physics. We perform the analysis for three types of problems: (1) the Travelling Salesman Problem, (2) vector quantization, and (3) traffic control problem in multistage interconnection network. In general, heuristic algorithms perform better (except for genetic algorithms) and much faster but have to be specific for every problem. The key to improving the performance could be to include heuristic features into general purpose statistical physics methods. (author)

Statistical model for expected un supplied energy; Statistisk modell for forventet ILE

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

Results from a statistical analysis of expected un supplied energy for Norwegian network companies are presented. The data are from the years 1996-2004. The estimation model includes several explanatory variables that together reflect the characteristics of the network, climatic aspects and other geographical conditions. The model has a high degree of accuracy when compared to the historical number of un supplied energy for about 90 percent of the network companies. But for 12 companies there are substantial, negative deviances that are not compatible with the available data. There is reason to believe that improved data for some types of variables can improve the accuracy of the model. In addition to establishing a norm for expected un supplied energy in the revenue estimations, the model can be used to reflect geographical constraints in NVEs (Norwegian Water and Energy directorate) efficiency analyses (ml)

Statistical mechanics for a class of quantum statistics

International Nuclear Information System (INIS)

Isakov, S.B.

1994-01-01

Generalized statistical distributions for identical particles are introduced for the case where filling a single-particle quantum state by particles depends on filling states of different momenta. The system of one-dimensional bosons with a two-body potential that can be solved by means of the thermodynamic Bethe ansatz is shown to be equivalent thermodynamically to a system of free particles obeying statistical distributions of the above class. The quantum statistics arising in this way are completely determined by the two-particle scattering phases of the corresponding interacting systems. An equation determining the statistical distributions for these statistics is derived

To compare effects of maitland and mulligan mobilization techniques in the treatment of frozen shoulder

International Nuclear Information System (INIS)

Haider, R.; Ahmad, A.

2014-01-01

To compare the role of Maitland mobilization and Mulligan's mobilization techniques in treatment of frozen shoulder and its possible effect in early gaining of ROM and Pain management. Methods: This was a randomized control trial conducted at Department of Physiotherapy ana Orthopedics unit I, KEMU / Mayo Hospital, Lahore. There were two group of patients each group contained 30 patients. Patients were treated with Mulligan's technique in Group - A and with Maitland manual therapy technique in Group - B. Patients in both treatment groups were followed till 6 weeks and improvement in range of motion parameters were recorded at every follow up visit of the patients. SPSS was used for data entry and analysis. Results: In the study 60 patients were enrolled. Mean age of Group - A patients was 46.23 ± 9.71 years, and mean age of Group - B patients was 47 ± 9.21 years. In Group - A 14 patients duration of onset was 8 weeks, 4 patients duration of onset was 10 weeks and 12 patients duration of onset was 12 weeks. In Group - B 14 patients duration of onset was 8 weeks, 8 patients duration of onset was 10 weeks and 12 weeks each respectively. It was observed that patients who were treated with Mulligan technique their abduction and flexion was improved greatly as compared to those who were treated with Maitland technique. Patients who were treated with Mulligan technique their flex- ion was improved greatly as compared to those who were treated with Maitland technique. At 6th week mean extension in Maitland's treatment group was 52.50 ± 8.66 where as that Mulligan's treatment group was 52.00 ± 7.58. It was observed that patients in both treatment groups had same improvement in extension and it was statistically same. In both treatment groups patients had same improvement in medial rotation and it was statistically same. At 6th week mean lateral rotation in both treatment groups was 42.65 ± 24.47 and 53.50 ± 23.03. It was observed that patients in

Anxiety and Attitude of Graduate Students in On-Campus vs. Online Statistics Courses

Science.gov (United States)

DeVaney, Thomas A.