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2006

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Articles 181 - 210 of 244

Full-Text Articles in Statistics and Probability

Comparing The Predictive Values Of Diagnostic Tests: Sample Size And Analysis For Paired Study Designs, Chaya S. Moskowitz, Margaret S. Pepe Feb 2006

Comparing The Predictive Values Of Diagnostic Tests: Sample Size And Analysis For Paired Study Designs, Chaya S. Moskowitz, Margaret S. Pepe

Memorial Sloan-Kettering Cancer Center, Dept. of Epidemiology & Biostatistics Working Paper Series

In this paper we consider the design and analysis of studies comparing the positive and negative predictive values of two diagnostic tests that are measured on all subjects. Although statistical methodology is well developed for comparing diagnostic tests in terms of their sensitivities and specificities, comparative inference about predictive values is not. We derive analytic variance expressions for the relative predictive values. Sample size formulas for study design ensue. In addition, two new methods for analyzing the resulting data are presented and compared with an existing marginal regression methodology.

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Regression Analysis For The Partial Area Under The Roc Curve, Tianxi Cai, Lori E. Dodd Feb 2006

Regression Analysis For The Partial Area Under The Roc Curve, Tianxi Cai, Lori E. Dodd

Harvard University Biostatistics Working Paper Series

No abstract provided.

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Gpnn: Power Studies And Applications Of A Neural Network Method For Detecting Gene-Gene Interactions In Studies Of Human Disease, Alison A. Motsinger, Stephen L. Lee, George Mellick, Marylyn D. Ritchie Jan 2006

Gpnn: Power Studies And Applications Of A Neural Network Method For Detecting Gene-Gene Interactions In Studies Of Human Disease, Alison A. Motsinger, Stephen L. Lee, George Mellick, Marylyn D. Ritchie

Dartmouth Scholarship

The identification and characterization of genes that influence the risk of common, complex multifactorial disease primarily through interactions with other genes and environmental factors remains a statistical and computational challenge in genetic epidemiology. We have previously introduced a genetic programming optimized neural network (GPNN) as a method for optimizing the architecture of a neural network to improve the identification of gene combinations associated with disease risk. The goal of this study was to evaluate the power of GPNN for identifying high-order gene-gene interactions. We were also interested in applying GPNN to a real data analysis in Parkinson's disease.

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Use Of Unbiased Estimating Equations To Estimate Correlation In Generalized Estimating Equation Analysis Of Longitudinal Trials, Wenguang Sun, Justine Shults, Mary Leonard Jan 2006

Use Of Unbiased Estimating Equations To Estimate Correlation In Generalized Estimating Equation Analysis Of Longitudinal Trials, Wenguang Sun, Justine Shults, Mary Leonard

UPenn Biostatistics Working Papers

In a recent publication, Wang and Carey (Journal of the American Statistical Association, 99, pp. 845-853, 2004) presented a new approach for estimation of the correlation parameters in the framework of generalized estimating equations (GEE). They considered correlated continuous, binary and count data with a generalized Markov correlation structure that includes the first-order autoregressive AR(1) and Markov structures as special cases. They made detailed comparisons with pseudo-likelihood (PL) and the first stage of quasi-least squares (QLS), a two-stage approach in the framework of generalized estimating equations (GEE). In this note we extend their comparisons for the second (bias corrected) stage …

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Correlating Factors Between Student Participation And Student Learning Via A Service Learning Project In Secondary Education: A Case Study, Shawn V. Jensen Jan 2006

Correlating Factors Between Student Participation And Student Learning Via A Service Learning Project In Secondary Education: A Case Study, Shawn V. Jensen

Theses and Dissertations

In this study a service-learning project was conducted with secondary students in a construction technology based course. Three research questions were considered; (1) does service learning projects help to engage student participation, (2) can students learn the course curriculum while participating in a service learning project, and (3) is there a correlation between student participation and student learning as it pertains to service learning projects? The data was collected through surveys, observations, interviews, and evaluations. The researcher concluded the following from the study; 92% of the students were actively participating in the two week service project, 76% of the students …

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Case-Cohort Methods For Survival Data On Families From Routine Registers, Tron Anders Moger, Yudi Pawitan, Ørnulf Borgan Jan 2006

Case-Cohort Methods For Survival Data On Families From Routine Registers, Tron Anders Moger, Yudi Pawitan, Ørnulf Borgan

UW Biostatistics Working Paper Series

In the Nordic countries, there exist several registers containing information on diseases and risk factors for millions of individuals. This information can be linked into families by use of personal identification numbers, and represent a great opportunity for studying diseases that show familial aggregation. Due to the size of the registers, it is difficult to analyze the data by using traditional methods for multivariate survival analysis, such as frailty or copula models. Since the size of the cohort is known, case-cohort methods based on pseudo-likelihoods are suitable for analyzing the data. We present methods for sampling control families both with …

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Comparison Of Haplotype-Based And Tree-Based Snp Imputation In Association Studies, James Y. Dai, Ingo Ruczinski, Michael Leblanc, Charles Kooperberg Jan 2006

Comparison Of Haplotype-Based And Tree-Based Snp Imputation In Association Studies, James Y. Dai, Ingo Ruczinski, Michael Leblanc, Charles Kooperberg

UW Biostatistics Working Paper Series

Missing single nucleotide polymorphisms (SNPs) are quite common in genetic association studies. Subjects with missing SNPs are often discarded in analyses, which may seriously undermine the inference of SNP-disease association. In this article, we compare two haplotype-based imputation approaches and one regression tree-based imputation approach for association studies. The goal is to assess the imputation accuracy, and to evaluate the impact of imputation on parameter estimation. Haplotype-based approaches build on haplotype reconstruction by the expectation-maximization (EM) algorithm or a weighted EM (WEM) algorithm, depending on whether case-control status is taken into account. The tree-based approach uses a Gibbs sampler to …

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On Self-Adjoint And J-Self-Adjoint Dirac-Type Operators: A Case Study, Stephen L. Clark, Fritz Gesztesy Jan 2006

On Self-Adjoint And J-Self-Adjoint Dirac-Type Operators: A Case Study, Stephen L. Clark, Fritz Gesztesy

Mathematics and Statistics Faculty Research & Creative Works

We provide a comparative treatment of some aspects of spectral theory for self-adjoint and non-self-adjoint (but J-self-adjoint) Dirac-type operators connected with the defocusing and focusing nonlinear Schrödinger equation, of relevance to nonlinear optics. In addition to a study of Dirac and Hamiltonian systems, we also introduce the concept of Weyl-Titchmarsh half-line m-coefficients (and 2 × 2 matrix-valued M-matrices) in the non-self-adjoint context and derive some of their basic properties. We conclude with an illustrative example showing that crossing spectral arcs in the non-self-adjoint context imply the blowup of the norm of spectral projections in the limit where the crossing point …

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Multiple Lebesgue Integration On Time Scales, Gusein Sh. Guseinov, Martin Bohner Jan 2006

Multiple Lebesgue Integration On Time Scales, Gusein Sh. Guseinov, Martin Bohner

Mathematics and Statistics Faculty Research & Creative Works

We study the process of multiple Lebesgue integration on time scales. The relationship of the Riemann and the Lebesgue multiple integrals is investigated.

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Singular Second-Order Multipoint Dynamic Boundary Value Problems With Mixed Derivatives, Hua Luo, Martin Bohner Jan 2006

Singular Second-Order Multipoint Dynamic Boundary Value Problems With Mixed Derivatives, Hua Luo, Martin Bohner

Mathematics and Statistics Faculty Research & Creative Works

We study a certain singular second-order m-point boundary value problem on a time scale and establish the existence of a solution. The proof of our main result is based upon the Leray-Schauder continuation theorem.

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Modeling Of Bioinspired Sensors For Flow Separation Detection For Micro Air Vehicles, Belinda A. Batten, John R. Singler, Benjamin T. Dickinson Jan 2006

Modeling Of Bioinspired Sensors For Flow Separation Detection For Micro Air Vehicles, Belinda A. Batten, John R. Singler, Benjamin T. Dickinson

Mathematics and Statistics Faculty Research & Creative Works

Autonomous micro air vehicle (MAV) flight faces inherent stability challenges. One challenge is controlling flow separation over the airfoil and an autonomous control system for MAV flight may be enhanced with closed loop separation control. In this work, we focus on modeling biologically inspired hair cell sensors for future flow control applications. We model the sensor output and present examples and numerical results.

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Feedback Control Of Low Dimensional Models Of Transition To Turbulence, John A. Burns, John R. Singler Jan 2006

Feedback Control Of Low Dimensional Models Of Transition To Turbulence, John A. Burns, John R. Singler

Mathematics and Statistics Faculty Research & Creative Works

The problem of controlling or delaying transition to turbulence in shear flows has been the subject of numerous papers over the past twenty years. This period has seen the development of several low dimensional models for parallel shear flows in an attempt to explain the failure of classical linear hydrodynamic stability theory to correctly predict transition. In recent years, ideas from robust control theory have been employed to attack this problem. In this paper we use these models to develop a scenario for transition that employs both classical bifurcation theory and robust control theory. In addition, we present numerical results …

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The Poweratlas: A Power And Sample Size Atlas For Microarray Experimental Design And Research, Grier P. Page, Jode W. Edwards, Gary L. Gadbury, Prashanth Yelisetti, Jelai Wang, Prinal Trivedi, David B. Allison Jan 2006

The Poweratlas: A Power And Sample Size Atlas For Microarray Experimental Design And Research, Grier P. Page, Jode W. Edwards, Gary L. Gadbury, Prashanth Yelisetti, Jelai Wang, Prinal Trivedi, David B. Allison

Mathematics and Statistics Faculty Research & Creative Works

Microarrays permit biologists to simultaneously measure the mRNA abundance of thousands of genes. An important issue facing investigators planning microarray experiments is how to estimate the sample size required for good statistical power. What is the projected sample size or number of replicate chips needed to address the multiple hypotheses with acceptable accuracy? Statistical methods exist for calculating power based upon a single hypothesis, using estimates of the variability in data from pilot studies. There is, however, a need for methods to estimate power and/or required sample sizes in situations where multiple hypotheses are being tested, such as in microarray …

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The Emergence Of Large-Scale Coherent Structure Under Small-Scale Random Bombardments, Andrew Majda, Xiaoming Wang Jan 2006

The Emergence Of Large-Scale Coherent Structure Under Small-Scale Random Bombardments, Andrew Majda, Xiaoming Wang

Mathematics and Statistics Faculty Research & Creative Works

We provide mathematical justification of the emergence of large-scale coherent structure in a two-dimensional fluid system under small-scale random bombardments with small forcing and appropriate scaling assumptions. the analysis shows that the large-scale structure emerging out of the small-scale random forcing is not the one predicted by equilibrium statistical mechanics. But the error is very small, which explains earlier successful prediction of the large-scale structure based on equilibrium statistical mechanics. © 2005 Wiley Periodicals, Inc.

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Dynamics Of Rotating Bose-Einstein Condensates And Its Efficient And Accurate Numerical Computation, Weizhu Bao, Qiang Du, Yanzhi Zhang Jan 2006

Dynamics Of Rotating Bose-Einstein Condensates And Its Efficient And Accurate Numerical Computation, Weizhu Bao, Qiang Du, Yanzhi Zhang

Mathematics and Statistics Faculty Research & Creative Works

In this paper, we study the dynamics of rotating Bose--Einstein condensates (BEC) based on the Gross--Pitaevskii equation (GPE) with an angular momentum rotation term and present an efficient and accurate algorithm for numerical simulations. We examine the conservation of the angular momentum expectation and the condensate width and analyze the dynamics of a stationary state with a shift in its center. By formulating the equation in either the two-dimensional polar coordinate system or the three-dimensional cylindrical coordinate system, the angular momentum rotation term becomes a term with constant coefficients. This allows us to develop an efficient time-splitting method which is …

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The Hurwitz Zeta Function As A Convergent Series, Roman Dwilewicz, Jan Minac Jan 2006

The Hurwitz Zeta Function As A Convergent Series, Roman Dwilewicz, Jan Minac

Mathematics and Statistics Faculty Research & Creative Works

New series for the Hurwitz zeta function which converge on the whole plane, except s = 1, are developed. This is applied to obtain a remarkably simple evaluation of some special values of the function.

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Impacts Of A Manure Composting Program On Stream Water Quality, A. Bekele, A. M.S. Mcfarland, A. J. Whisenant Jan 2006

Impacts Of A Manure Composting Program On Stream Water Quality, A. Bekele, A. M.S. Mcfarland, A. J. Whisenant

Faculty Publications

In February 2001, the Texas Commission on Environmental Quality (TCEQ) adopted a Total Maximum Daily Load (TMDL) for soluble reactive phosphorus (SRP) along the North Bosque River. Within this TMDL, dairy waste application fields were identified as the major nonpoint-source contribution of nutrients. In September 2000, a manure composting program was initiated that resulted in about 500,000 metric tons of dairy manure being hauled to composting facilities and exported from the watershed through December 2004. To evaluate the impact of the manure composting program on stream water quality, storm event mean concentrations of nutrients and total suspended solids were compared …

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Atomic Hardy Space Theory For Unbounded Singular Integrals, Ryan Berndt Jan 2006

Atomic Hardy Space Theory For Unbounded Singular Integrals, Ryan Berndt

Mathematics Faculty Scholarship

No abstract provided.

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Variation In The U.S. Photoperiod Insensitive Sorghum Collection For Chemical And Nutritional Traits, Tisha L. Hooks, Jeffrey F. Pedersen, D. B. Marx, K. P. Vogel Jan 2006

Variation In The U.S. Photoperiod Insensitive Sorghum Collection For Chemical And Nutritional Traits, Tisha L. Hooks, Jeffrey F. Pedersen, D. B. Marx, K. P. Vogel

Department of Statistics: Faculty Publications

Screening germplasm for chemical and nutritional content can be expensive and time consuming. Near infrared spectroscopy (NIRS) and application of geostatistical models can make screening more efficient. The objectives of this study were to utilize these technologies to: (i) generate chemical and nutritional values for the U.S. photoperiod insensitive sorghum collection, (ii) describe variability for those traits, (iii) identify accessions in the highest and lowest 1% for each trait, and (iv) describe relationships among the accessions. Accessions were grown at Ithaca, NE, during 2001 and 2002. Samples of grain were scanned and NIRS equations developed for starch, fat, crude protein, …

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Trans-10, Cis-12 Conjugated Linoleic Acid Causes Inflammation And Delipidation Of White Adipose Tissue In Mice: A Microarray And Histological Analysis, P. Christopher Larosa, Jess L. Miner, Yuannan Xia, You Zhou, Stephen D. Kachman, Michael Fromm Jan 2006

Trans-10, Cis-12 Conjugated Linoleic Acid Causes Inflammation And Delipidation Of White Adipose Tissue In Mice: A Microarray And Histological Analysis, P. Christopher Larosa, Jess L. Miner, Yuannan Xia, You Zhou, Stephen D. Kachman, Michael Fromm

Department of Statistics: Faculty Publications

A combined histological and microarray analysis of the white adipose tissue (WAT) of mice fed trans-10, cis-12 conjugated linoleic acid (t10c12 CLA) was performed to better define functional responses. Mice fed t10c12 CLA for 14 days lost 85% of WAT mass, 95% of adipocyte lipid droplet volume, and 15 or 47% of the number of adipocytes and total cells, respectively. Microarray profiling of replicated pools (n = 2 per day x diet) of control and treated mice (n = 140) at seven time points after 1–17 days of t10c12 CLA feeding found between 2,682 and 4,216 …

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Pregnancy Rate And First-Service Conception Rate In Angus Heifers, J. Minick Bormann, L. R. Totir, Stephen D. Kachman, R. L. Fernando, D. E. Wilson Jan 2006

Pregnancy Rate And First-Service Conception Rate In Angus Heifers, J. Minick Bormann, L. R. Totir, Stephen D. Kachman, R. L. Fernando, D. E. Wilson

Department of Statistics: Faculty Publications

The objective of this project was to determine the genetic control of conception rate, or pregnancy percentage in Angus beef heifers. Producers from 6 herds in 5 states provided 3,144 heifer records that included breeding dates, breeding contemporary groups, service sires, and pregnancy check information. Two hundred fourteen sires of the heifers were represented; with 104 sires having less than 5 progeny, and 14 sires having greater than 50 progeny. These data were combined with performance and pedigree information, including actual and adjusted birth weights, weaning weights, and yearling weights, from the American Angus Association database. Heifer pregnancy rate varied …

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Closed Form Expressions For Bayesian Sample Size, Bertrand S. Clarke, A. Yuan Jan 2006

Closed Form Expressions For Bayesian Sample Size, Bertrand S. Clarke, A. Yuan

Department of Statistics: Faculty Publications

Sample size criteria are often expressed in terms of the concentration of the posterior density, as controlled by some sort of error bound. Since this is done pre-experimentally, one can regard the posterior density as a function of the data. Thus, when a sample size criterion is formalized in terms of a functional of the posterior, its value is a random variable. Generally, such functionals have means under the true distribution. We give asymptotic expressions for the expected value, under a fixed parameter, for certain types of functionals of the posterior density in a Bayesian analysis. The generality of our …

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Reliability For Some Bivariate Exponential Distributions, Saralees Nadarajah, Samuel Kotz Jan 2006

Reliability For Some Bivariate Exponential Distributions, Saralees Nadarajah, Samuel Kotz

Department of Statistics: Faculty Publications

In the area of stress-strength models, there has been a large amount of work as regards estimation of the reliability R = Pr(X < Y). The algebraic form for R = Pr(X < Y) has been worked out for the vast majority of the well-known distributions when X and Y are independent random variables belonging to the same univariate family. In this paper, forms of R are considered when (X,Y) follow bivariate distributions with dependence between X and Y. In particular, explicit expressions for R are derived when the joint distribution is bivariate …

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Quotient Of Laplace And Gumbel Random Variables, Saralees Nadarajah Jan 2006

Quotient Of Laplace And Gumbel Random Variables, Saralees Nadarajah

Department of Statistics: Faculty Publications

The Gumbel and the Laplace distributions are perhaps two of the most applied distributions in engineering. Motivated by engineering issues, the exact distribution of the quotient |X/Y| is derived when X and Y are independent Gumbel and Laplace random variables. Tabulations of the associated percentage points and a computer program for generating them are also given.

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Ua56/1 Fact Book, Wku Institutional Research Jan 2006

Ua56/1 Fact Book, Wku Institutional Research

WKU Administration Documents

Statistical and demographic profile of WKU.

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A Peano-Akô Type Theorem For Variational Inequalities, Vy Khoi Le Jan 2006

A Peano-Akô Type Theorem For Variational Inequalities, Vy Khoi Le

Mathematics and Statistics Faculty Research & Creative Works

We consider in this paper a Peano-Akô property of solution sets in some quasilinear elliptic variational inequalities. As consequences, variants of that property and a partial Hukuhara-Kneser theorem for inequalities are derived.

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Boundedness In Functional Dynamic Equations On Time Scales, Elvan Akin, Youssef N. Raffoul Jan 2006

Boundedness In Functional Dynamic Equations On Time Scales, Elvan Akin, Youssef N. Raffoul

Mathematics and Statistics Faculty Research & Creative Works

Using nonnegative definite Lyapunov functionals, we prove general theorems for the boundedness of all solutions of a functional dynamic equation on time scales. We apply our obtained results to linear and nonlinear Volterra integro-dynamic equations on time scales by displaying suitable Lyapunov functionals.

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Computation Of A Face Attractiveness Index Based On Neoclassical Canons, Symmetry, And Golden Ratios, Kendra Schmid, David Marx, Ashok Samal Jan 2006

Computation Of A Face Attractiveness Index Based On Neoclassical Canons, Symmetry, And Golden Ratios, Kendra Schmid, David Marx, Ashok Samal

Department of Statistics: Faculty Publications

Analysis of attractiveness of faces has long been a topic of research. Literature has identified many different factors that can be related to attractiveness including symmetry, averageness, sexual dimorphism and adherence to the Golden Ratio. In this research we systematically analyze the role of three factors: symmetry, conformance to Neoclassical Canons and the Golden Ratio in the determination of attractiveness of a face. Unlike many researchers, we focus on the geometry of a face and use actual faces in standardized databases for our analysis. Our results are in agreement with the literature in that males and females generally agree on …

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Analyzing Dna Microarrays With Undergraduate Statisticians, Johanna S. Hardin, Laura Hoopes, Ryan Murphy '06 Jan 2006

Analyzing Dna Microarrays With Undergraduate Statisticians, Johanna S. Hardin, Laura Hoopes, Ryan Murphy '06

Pomona Faculty Publications and Research

With advances in technology, biologists have been saddled with high dimensional data that need modern statistical methodology for analysis. DNA microarrays are able to simultaneously measure thousands of genes (and the activity of those genes) in a single sample. Biologists use microarrays to trace connections between pathways or to identify all genes that respond to a signal. The statistical tools we usually teach our undergraduates are inadequate for analyzing thousands of measurements on tens of samples. The project materials include readings on microarrays as well as computer lab activities. The topics covered include image analysis, filtering and normalization techniques, and …

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Yeast Through The Ages: A Statistical Analysis Of Genetic Changes In Aging Yeast, Alison Wise '05, Johanna S. Hardin, Laura Hoopes Jan 2006

Yeast Through The Ages: A Statistical Analysis Of Genetic Changes In Aging Yeast, Alison Wise '05, Johanna S. Hardin, Laura Hoopes

Pomona Faculty Publications and Research

Microarray technology allows for the expression levels of thousands of genes in a cell to be measured simultaneously. The technology provides great potential in the fields of biology and medicine, as the analysis of data obtained from microarray experiments gives insight into the roles of specific genes and the associated changes across experimental conditions (e.g., aging, mutation, radiation therapy, drug dosage). The application of statistical tools to microarray data can help make sense of the experiment and thereby advance genetic, biological, and medical research. Likewise, microarrays provide an exciting means through which to explore statistical techniques.

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