Statistics and Probability Commons^™

Special Education Distributions And Analysis, Valerie Felder, Shlomo S. Sawilowsky

Journal of Modern Applied Statistical Methods

Micceri (1989) examined the distributional characteristics of 440 large sample general education achievement and psychometric measures. All the distributions were found to be statistically significantly different from the normal distribution. In this study, 395 special education datasets were examined. Although there were some normally distributed datasets, most were not, and some were markedly different in shape from those found by Micceri (1989). Implications for statistical testing and making special education policy decisions were given.

Vol. 14, No. 1 (Full Issue), Jmasm Editors

Journal of Modern Applied Statistical Methods

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A Comparison Of Semi-Parametric And Nonparametric Methods For Estimating Mean Time To Event For Randomly Left Censored Data, Farzana Chowdhury, Jahida Gulshan, Syed Shahadat Hossain

Journal of Modern Applied Statistical Methods

The aim of this study was to make a comparison among existing estimation methods (Kaplan-Meier, Nelson-Aalen and Regression on Ordered Statistics (ROS)) for randomly left censored time to event data under selected distributions and for different level of censoring and sample sizes in order to determine the strength of these methods based on simulated data. Comparisons among the methods are made on the basis of unbiasedness and Monte Carlo Standard Error of the summary statistics (mean time to event) obtained by those methods under different conditions.

Incorporating Relaxivities To More Accurately Reconstruct Mr Images, Muge Karaman, Iain P. Bruce, Daniel B. Rowe

Mathematics, Statistics and Computer Science Faculty Research and Publications

Purpose

To develop a mathematical model that incorporates the magnetic resonance relaxivities into the image reconstruction process in a single step.

Materials and methods

In magnetic resonance imaging, the complex-valued measurements of the acquired signal at each point in frequency space are expressed as a Fourier transformation of the proton spin density weighted by Fourier encoding anomalies: T₂^⁎, T₁, and a phase determined by magnetic field inhomogeneity (∆B) according to the MR signal equation. Such anomalies alter the expected symmetry and the signal strength of the k-space observations, resulting in images distorted …

The Minimal Zn-Symmetric Graphs That Are Not Zn-Spherical, Lowell Abrams, Dan Slilaty

Mathematics and Statistics Faculty Publications

Given a graph G equipped with faithful and fixed-point-free Γ-action (Γ a finite group) we define an orbit minor H of G to be a minor of G for which the deletion and contraction sets are closed under the Γ-action. The orbit minor H inherits a Γ-symmetry from G, and when the contraction set is acyclic the action inherited by H remains faithful and fixed-point free. When G embeds in the sphere and the Γ-action on G extends to a Γ-action on the entire sphere, we say that G is Γ-spherical. In this paper we determine for every odd value …

Analytical Comparison Of Contrasting Approaches To Estimating Competing Risks Models, Brian Stephen Rickard

Graduate Theses and Dissertations

Survival analysis is a commonly used tool in many fields but has seen little use in education research despite a common number of research questions for which it is well suited. Researchers often use logistic regression instead; however, this omits useful information. In research on retention and graduation for example, the timing of the event is an important piece of information omitted when using logistic regression. A simulation study was conducted to evaluate four methods of analyzing competing risks survival data, Cox proportional hazards regression, Weibull regression, Fine and Gray's Method, and Cox proportional hazards regression with frailty. College student …

A Comparison Of Population-Averaged And Cluster-Specific Approaches In The Context Of Unequal Probabilities Of Selection, Natalie A. Koziol

College of Education and Human Sciences: Dissertations, Theses, and Student Research

Sampling designs of large-scale, federally funded studies are typically complex, involving multiple design features (e.g., clustering, unequal probabilities of selection). Researchers must account for these features in order to obtain unbiased point estimators and make valid inferences about population parameters. Single-level (i.e., population-averaged) and multilevel (i.e., cluster-specific) methods provide two alternatives for modeling clustered data. Single-level methods rely on the use of adjusted variance estimators to account for dependency due to clustering, whereas multilevel methods incorporate the dependency into the specification of the model.

Although the literature comparing single-level and multilevel approaches is vast, comparisons have been limited to the …

A New Approach To Modeling Multivariate Time Series On Multiple Temporal Scales, Tucker Zeleny

Department of Statistics: Dissertations, Theses, and Student Research

In certain situations, observations are collected on a multivariate time series at a certain temporal scale. However, there may also exist underlying time series behavior on a larger temporal scale that is of interest. Often times, identifying the behavior of the data over the course of the larger scale is the key objective. Because this large scale trend is not being directly observed, describing the trends of the data on this scale can be more difficult. To further complicate matters, the observed data on the smaller time scale may be unevenly spaced from one larger scale time point to the …

Failing To Replicate: Hypothesis Testing As A Crucial Key To Make Direct Replications More Credible And Predictable, Pedro Fernando Mateu Bullón

Dissertations

Theory cannot be fully validated unless the original results have been replicated, resulting in conclusion consistency. Replications are the strongest source to verify research findings and knowledge claims. Sciences such as medicine, chemistry, physics, genetics, and biology, are considered successful because their knowledge claims are buttressed by a large set of replications of original studies. Unfortunately in the social sciences many attempts to replicate fail and thus there is a continuing need for replication studies to confirm facts, expand knowledge to gain new understanding, and verify hypotheses. Two plausible explanations for the failure to replicate in the social sciences could …

Three Essays On Panel Data Estimation, Alexander Houser

Dissertations

This work discusses various aspects of panel data estimation. In chapter one, an algorithm for semiparametric random effects estimation is proposed. The performance of bootstrap-based confidence intervals for the proposed estimators are examined and found reasonable. The algorithm is also applied to a set of U.S. state level medical expenditure data to estimate the medical Engel curve. In the second chapter, the predictive performance of various parametric and semiparametric panel data estimators is compared on the same dataset of U.S. state level medical expenditures as well as out of sample forecast performance and bootstrap bias-corrected mean square errors of the …

Genetics Of Obesity In Starr County, Texas Mexican Americans, Heather M. Highland

Dissertations and Theses (Open Access)

Currently, over two-thirds of Americans are classified as over-weight or obese. Obesity increases risk for many other diseases including type 2 diabetes, heart disease, stroke, and cancer, making obesity the largest public health problem in America and most other Westernized nations. Hispanics have a higher rate of both obesity and type 2 diabetes, making them a particularly interesting population in which to study obesity. For the last 33 years, the Starr County Health Studies has collected an array of phenotypes and biological samples from residents of Starr County, along Texas-Mexico border. This study includes 825 subjects who were not known …

Average Case Network Lifetime On An Interval With Adjustable Sensing Ranges, Amotz Bar-Noy, Benjamin Baumer

Mathematics Sciences: Faculty Publications

Given n sensors on an interval, each of which is equipped with an adjustable sensing radius and a unit battery charge that drains in inverse linear proportion to its radius, what schedule will maximize the lifetime of a network that covers the entire interval? Trivially, any reasonable algorithm is at least a 2-approximation for this Sensor Strip Cover problem, so we focus on developing an efficient algorithm that maximizes the expected network lifetime under a random uniform model of sensor distribution. We demonstrate one such algorithm that achieves an expected network lifetime within 12 % of the theoretical maximum. Most …

Optcluster : An R Package For Determining The Optimal Clustering Algorithm And Optimal Number Of Clusters., Michael N. Sekula

Electronic Theses and Dissertations

Determining the best clustering algorithm and ideal number of clusters for a particular dataset is a fundamental difficulty in unsupervised clustering analysis. In biological research, data generated from Next Generation Sequencing technology and microarray gene expression data are becoming more and more common, so new tools and resources are needed to group such high dimensional data using clustering analysis. Different clustering algorithms can group data very differently. Therefore, there is a need to determine the best groupings in a given dataset using the most suitable clustering algorithm for that data. This paper presents the R package optCluster as an efficient …

Summary Of Survival Analysis With Sas Procedures., Derek Duane Childers 1990-

Electronic Theses and Dissertations

The research conducted for this thesis was performed to summarize some of the most commonly used survival analysis techniques as well as to create one macro that will provide the solutions for these techniques. Some of the techniques that this thesis focuses on are survival and hazard functions, mean and median survival times, life table, log rank test, proportional hazards/model building, and competing risk. To further analyze these survival analysis techniques I will use the Bone Marrow Transplantation for Leukemia dataset. This trial consists of either acute myelocytic leukemia (AML 99 patients) or acute lymphoblastic leukemia (ALL 38 patients). There …

Mindsets, Attitudes, And Achievement In Undergraduate Statistics Courses, Valorie L. Zonnefeld

Faculty Work Comprehensive List

The purpose of this study was to determine the effects of theories of intelligence and an intervention of incremental mindset training on students’ attitudes toward statistics and their mastery of content in an introductory statistics college course. The sample was 547 undergraduate students at a small, faith-based, liberal arts college in the Midwest.

A pretest-posttest design was used for the three instruments implemented. The Comprehensive Assessment of Outcomes in a first Statistics course (CAOS) assessed students’ statistical literacy. The Student Attitudes Towards Statistics – 36© (SATS©) assessed six components of students’ attitudes toward statistics including affect, cognitive competence, difficulty, effort, …

Survival Analysis For Truncated Data And Competing Risks, Michael Steelman

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

The purpose of this project is to consider the problems of left truncation and competing risks in analyzing censored survival data, and to compare and contrast various approaches for handling these problems. The motivation for this work comes from an analysis of data from the Cache County Memory Study. Study investigators were interested in the association between early-life psychologically stressful events (e.g., parental or sibling death, or parental divorce, among others) and late-life risk of Alzheimer's disease (AD). While conventional methods for censored survival data can be applied, the presence of left truncation and competing risks (i.e., other adverse events …

Comparing Linear Mixed Models To Meta-Regression Analysis In The Greenville Air Quality Study, Lynsie M. Daley

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

The effect of air quality on public health is an important issue in need of better understanding. There are many stakeholders, especially in Utah and Cache Valley, where the poor air quality as measured by PM 2.5 levels and consequent inversions can sometimes be the very worst in the nation. This project focuses on comparing two statistical methods used to analyze an important air quality data set from the Greenville Air Quality Study, focusing on a lung function response variable. A linear mixed model, with a random factor for subject, gives slope estimates and their significance for predictor variables of …

The Effects Of Instruction On Landing Strategies In Female College-Aged Dancers And Non-Dancers: A Pilot Study, Brittany Keating, Jason Pyfer, Kimberly Vialpando

UNLV Theses, Dissertations, Professional Papers, and Capstones

Background Female athletic participation has increased over the past decade and with it the prevalence of knee injuries. Current research demonstrates an increased risk of anterior cruciate ligament (ACL) injury for female athletes. However, a number of studies have pointed out that ballet and modern dancers exhibit a lower incidence of ACL injuries despite the fact that they perform jumping and landing frequently.

Objective The objective of this study was to examine how dance experience and instruction affect the lower extremity biomechanics during drop landings. Specifically, lower extremity joint alignment and muscle activation of gluteus maximus and gluteus medius were …

The Effects Of Enhanced And Decreased Expectations On Balance Performance In Those With And Without Parkinson’S Disease, Joshua Ostrander, Granuaile Parrish, Jacob Blood

UNLV Theses, Dissertations, Professional Papers, and Capstones

Background: It has been reported individuals typically perform well on a task when enhanced expectancy was provided prior to task performance. It has also been reported people with Parkinson’s disease (PD) are especially susceptible to pre-task placebo cuing and suggestion. Evidence of this susceptibility has been previously demonstrated through brain imaging studies and with demonstration by individuals with PD improved balance performance.

Objective: This study was designed to further previous studies’ results for improved task performance with enhanced expectancy. The purpose of this study was to investigate if the pre-task verbal delivery of enhanced expectancy, decreased expectancy and no expectancy …

Patient No-Show For Outpatient Physical Therapy: A National Survey, James Bokinskie, Payton Johnson, Trevor Mahoney

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: Patients who fail to show for scheduled medical appointments (no-show) create a cascade of issues for the health care system, the provider, and themselves. No-show can affect clinical productivity, cost and quality of care, and treatment outcomes. There is an overwhelming lack of research on no-show as it relates to outpatient physical therapy in the United States. The purposes of this study were to report national no-show rates, describe the presence and characteristics of no-show policies, determine the relationship of these policies and other demographic information to no-show rates, and describe the most commonly perceived reasons for no-show.

Methods: …