Physical Sciences and Mathematics Commons^™

An Adaptive Bayesian Approach To Dose-Response Modeling, Thomas J. Leininger

Theses and Dissertations

Clinical drug trials are costly and time-consuming. Bayesian methods alleviate the inefficiencies in the testing process while providing user-friendly probabilistic inference and predictions from the sampled posterior distributions, saving resources, time, and money. We propose a dynamic linear model to estimate the mean response at each dose level, borrowing strength across dose levels. Our model permits nonmonotonicity of the dose-response relationship, facilitating precise modeling of a wider array of dose-response relationships (including the possibility of toxicity). In addition, we incorporate an adaptive approach to the design of the clinical trial, which allows for interim decisions and assignment to doses based …

A Two-Sample Adaptive Procedure Based On The Log-Rank And Peto And Peto's Wilcoxon Tests, Annie A. Tordilla

Dissertations

It has been shown that under a location-scale model y = μ + βz + σε at where y is right censored, the Log-Rank test is asymptotically efficient for the Extreme minimum value error distribution while Peto and Peto's Wilcoxon test is asymptotically efficient for the Logistic error distribution. We propose a two-sample adaptive test, which first selects between Extreme minimum value and Logistic error distribution as to which is a better fit to the data, then performs the asymptotically efficient test (Log-Rank or Peto and Peto's Wilcoxon test) for the selected distribution. The performance of the adaptive test is …

Metaevaluation Of Hiv/Aids Prevention Intervention Evaluations In Sub Saharan Africa With A Specific Emphasis On Implications For Women And Girls, Tererai Mafukidze Trent

Dissertations

Despite numerous attempts by international agencies to halt the spread of Human Immunodeficiency Virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS), nowhere has the impact of HIV/AIDS been felt more acutely than among women and girls in Sub-Saharan Africa (SSA). SSA women account for 59% of adults over the age of 15 living with HIV/AIDS and 76% of those 15-24 who are infected (United Nations Joint Programme on HIV/AIDS [UNAIDS], 2007).

The evidence on gender disparities in infection rates is indisputable; there is an urgent need to identify what is missing in HIV/AIDS prevention interventions: What is the evidence based upon …

On The Testing And Estimation Of High-Dimensional Covariance Matrices, Thomas Fisher

All Dissertations

Many applications of modern science involve a large number of parameters. In
many cases, the number of parameters, p, exceeds the number of observations,
N. Classical multivariate statistics are based on the assumption that the
number of parameters is fixed and the number of observations is large. Many of
the classical techniques perform poorly, or are degenerate, in high-dimensional
situations.
In this work, we discuss and develop statistical methods for inference of
data in which the number of parameters exceeds the number of observations.
Specifically we look at the problems of hypothesis testing regarding and the
estimation of the covariance …

Statistical Analysis Of Linear Analog Circuits Using Gaussian Message Passing In Factor Graphs, Miti Phadnis

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis introduces a novel application of factor graphs to the domain of analog circuits. It proposes a technique of leveraging factor graphs for performing statistical yield analysis of analog circuits that is much faster than the standard Monte Carlo/Simulation Program With Integrated Circuit Emphasis (SPICE) simulation techniques. We have designed a tool chain to model an analog circuit and its corresponding factor graph and then use a Gaussian message passing approach along the edges of the graph for yield calculation. The tool is also capable of estimating unknown parameters of the circuit given known output statistics through backward message …

The Program Evaluation Standards Applied For Metaevaluation Purposes: Investigating Interrater Reliabiity And Implications For Use, Lori A. Wingate

Dissertations

Metaevaluation is the evaluation of evaluation. Metaevaluation may focus particular evaluation cases, evaluation systems, or the discipline overall. Leading scholars within the discipline consider metaevaluation to be a professional imperative, demonstrating that evaluation is a reflexive enterprise. Various criteria have been set forth for what constitutes excellence in evaluation. In the context of educational program evaluation, the dominant criteria are the Program Evaluation Standards, developed by the developed by the Joint Committee on Standards for Educational Evaluation.

There has been widespread acceptance and application of the Program Evaluation Standards, and their use is advocated by major organizations and several of …

Kendall's Tau And Spearman's Rho For Zero-Inflated Data, Ronald Silva Pimentel

Dissertations

Zero-inflated continuous distributions have positive probability mass at zero in addition to a continuous distribution. Such type of data can be encountered, for example, in medical, environmental and financial research. The main focus of this research is to study the association of nonnegative random variables, both having a positive probability mass at zero. New estimators of the classical measures of association, Kendall's tau and Spearman's rho, appropriate for the zero-inflated distributions, are proposed and their asymptotic distributions are derived. Performance of the estimators is assessed by a Monte Carlo simulation study. New ideas are illustrated by a real data example.

A Statistical Analysis Of Key Factors Influencing The Location Of Biomass-Using Facilities, Xu Liu

Masters Theses

Bioenergy and biofuels are emerging industries in the U.S. economy that will require statistical and economical analyses of woody biomass resources, supply chains, and other key factors that influence the siting of industrial facilities. This thesis develops models using logistic regression to improve the understanding of the key factors that influence the locations of existing wood-using bioenergy and biofuels plants, and other wood-using plants. The scope of the study is 13 Southeastern states.¹ Logistic regression models are developed at the state and regional levels. The resolution of the study is the ZIP Code tabulation area (ZCTA). There are 9,416 …

The Development Of An Advanced Filial Therapy Model, Amy Cathleen Wickstrom

Loma Linda University Electronic Theses, Dissertations & Projects

This study sought to develop an advanced filial therapy model by examining the experiences of seven parents who participated in a preliminary advanced filial therapy intervention. These parents had previously completed a 10-week basic filial therapy model called Child Parent Relationship Therapy. A phenomenological qualitative design was employed, wherein data was obtained from parent playtime notes, researcher field notes, group process transcriptions, and focus groups. Parent experiences of the intervention were examined from a systems-relational lens, and four categories emerged, which include relational epiphanies, enhanced understanding of the playtimes, model format, and skill development. Additionally, a variety of themes were …

Nonlinear Models In Multivariate Population Bioequivalence Testing, Bassam Dahman

Theses and Dissertations

In this dissertation a methodology is proposed for simultaneously evaluating the population bioequivalence (PBE) of a generic drug to a pre-licensed drug, or the bioequivalence of two formulations of a drug using multiple correlated pharmacokinetic metrics. The univariate criterion that is accepted by the food and drug administration (FDA) for testing population bioequivalence is generalized. Very few approaches for testing multivariate extensions of PBE have appeared in the literature. One method uses the trace of the covariance matrix as a measure of total variability, and another uses a pooled variance instead of the reference variance. The former ignores the correlation …

Parameter Estimation For The Lognormal Distribution, Brenda Faith Ginos

Theses and Dissertations

The lognormal distribution is useful in modeling continuous random variables which are greater than or equal to zero. Example scenarios in which the lognormal distribution is used include, among many others: in medicine, latent periods of infectious diseases; in environmental science, the distribution of particles, chemicals, and organisms in the environment; in linguistics, the number of letters per word and the number of words per sentence; and in economics, age of marriage, farm size, and income. The lognormal distribution is also useful in modeling data which would be considered normally distributed except for the fact that it may be more …

Joint Mixed-Effects Models For Longitudinal Data Analysis: An Application For The Metabolic Syndrome, John Thorp Iii

Theses and Dissertations

Mixed-effects models are commonly used to model longitudinal data as they can appropriately account for within and between subject sources of variability. Univariate mixed effect modeling strategies are well developed for a single outcome (response) variable that may be continuous (e.g. Gaussian) or categorical (e.g. binary, Poisson) in nature. Only recently have extensions been discussed for jointly modeling multiple outcome variables measures longitudinally. Many diseases processes are a function of several factors that are correlated. For example, the metabolic syndrome, a constellation of cardiovascular risk factors associated with an increased risk of cardiovascular disease and type 2 diabetes, is often …

Investigation Of Mlb Data With Multivariate Statistics, Vincent Milano

Statistics

A statistical study was performed in order to explore the relationships of the offensive player statistics for every player in the 2008 Major League Baseball season. The purpose of the study was to explore various multivariate statistical methods within the data set.

The offensive variables in the study are: games, at-bats, runs, hits, singles, doubles, triples, homeruns, extra base hits, runs batted in, total bases, walks, strikeouts, stolen bases, times caught stealing, on-base percentage, slugging percentage, on-base plus slugging percentage, and batting average. All variables are season totals except for onbase percentage, slugging percentage, on-base plus slugging, and batting average. …

Deriving Optimal Composite Scores: Relating Observational/Longitudinal Data With A Primary Endpoint, Rhonda Ellis

Theses and Dissertations

In numerous clinical/experimental studies, multiple endpoints are measured on each subject. It is often not clear which of these endpoints should be designated as of primary importance. The desirability function approach is a way of combining multiple responses into a single unitless composite score. The response variables may include multiple types of data: binary, ordinal, count, interval data. Each response variable is transformed to a 0 to1 unitless scale with zero representing a completely undesirable response and one representing the ideal value. In desirability function methodology, weights on individual components can be incorporated to allow different levels of importance to …

Impact Of Ambient Air Pollution On Survival Of Renal Transplant Recipients, Rhonda Kristine Hwang

Loma Linda University Electronic Theses, Dissertations & Projects

There is increasing evidence that ambient air pollution is associated with coronary heart disease morbidity and mortality. This research has focused on the general public and less so on possible sensitive subgroups even though these may have even greater susceptibility to adverse effects of ambient air pollution. With highly prevalent traditional as well as nontraditional risk factors, renal transplant recipients may potentially be a sensitive subgroup. The purpose of this study was to evaluate the possible effect of between long-term exposure to air pollution on the risk of CHD mortality among renal transplant recipients. This cohort study includes 32,239 adult, …

Neurodevelopmental Outcome & Mr Spectroscopy Of Therapeutic Hypothermia After Pediatric Drowning, Sharon Mieras Perugini

Loma Linda University Electronic Theses, Dissertations & Projects

Despite advances in medical treatment and technology, outcome following pediatric drowning can vary widely from mild to severe impairments and death. Prognosis is often difficult to predict given a number of contributing factors. As such, this study examined the relationship between clinical indicators including submersion duration, initial GCS and PRISM scores, and waking time with outcome as well as metabolite ratios based on magnetic resonance spectroscopy. Research stemming from the area of cardiac arrest as well as anecdotal case study reports of cold water drownings suggests that lowering the body temperature may be helpful and protective. As such, the use …

Observer Reliability Of Cephalometric Landmark Identification On 3-D Mr Images, Michael S. Pollack

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Cephalometric analysis is a cornerstone of orthodontic diagnosis, yet much information is lost when 3-dimensional structures are assessed with 2-dimensional methods. CBCT offers 3-dimensional imaging but at the cost of higher levels of ionizing radiation. Magnetic resonance imaging provides 3-dimensional imaging without ionizing radiation and additionally imparts visualization of soft tissue structures. Prior to employing MR images for cephalometric analysis, reliability of landmark identification must be assessed. The purpose of this study was to evaluate intra- and interobserver reliability in 3-dimensional landmark identification using MR images.

Materials and Methods: Fifteen cranial MR images (3.0 T, MP-RAGE) from subjects between …

Using Cone Beam Computed Tomography To Identify A Prediction Model For Obstructive Sleep Apnea, Jodi Parker

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Obstructive Sleep Apnea (OSA) patients have increased risk of morbidity and mortality. Early diagnosis may reduce morbidity and mortality. Prediction of OSA from imaging may help to identify OSA patients earlier in life. CBCT can be used for OSA diagnostic imaging due to its three-dimensional (3D) visualization of the upper airway and craniofacial complex. Magnification associated with conventional 2D radiography is eliminated with CBCT, and radiation to the patient is significantly less than previous modalities used to measure craniofacial & airway measurements associated with OSA. During a CBCT scan, the patient's image is taken supine, rather than the upright …

Profiles Of Drug Endangered Children: Investigation In A Clinical Sample, Imanie Samanmali Wijayaratne

Loma Linda University Electronic Theses, Dissertations & Projects

Despite the increase in children born prenatally exposed to methamphetamine, little is known about the cognitive and neuropsychological outcomes of these children. Research specific to prenatal-methamphetamine exposure is extremely limited and has been primarily restricted to rat studies. This research combined with the few studies examining children prenatally exposed to methamphetamine suggests that methamphetamine-exposure is associated with various cognitive and neuropsychological delays and is impacted by both biological and environmental factors. Given the scarcity of research in this area, the current study used archival data from a psychological assessment clinic to (1) describe the frequency of prenatal methamphetamine-exposure cases, (2) …

Comparison Of Rationally-Derived And Empirically-Derived Methods For Predicting Failure In Residential Treatment, Jennifer Pester Grattan

Loma Linda University Electronic Theses, Dissertations & Projects

Patient-focused research methods have been used in adult mental health treatment to improve outcomes by tracking individual treatment response and comparing it with expected recovery patterns. One such approach has used rationally- and empirically-derived methods to analyze data from the OQ-45 and identify patients who are not responding as expected to treatment. Treatment is then adjusted, improving outcomes and lowering overall costs.

Similar but less extensive research has shown analogous methods can be used with children and adolescents. This would be particularly useful in residential treatment, which is an expensive and inadequately researched approach. This study used archival data gathered …

Study Of The Four Factor Theory Of Women’S Sexual Function, Julie M. Merrell

Loma Linda University Electronic Theses, Dissertations & Projects

Tiefer, Hall, and Tavris (2002) described factors comprising four categories of female sexual function. They suggested that unique factors need to be examined to understand sexual function in women. Socio-cultural, political, or economic factors, partner and relationship factors, psychological factors, and medical factors were described as aspects of women’s lives that can be the source of sexual dysfunction. In a previous study, Merrell (2007) utilized Tiefer et al’s (2002) four factor model of sexual functioning to examine female sexual functioning looking specifically at body shame, relationship satisfaction, positive and negative affect, sexual self-schema, and overall health. Based on the results …

The Effects Of Physical Activity And Nutrient Intake On The Risk Of Hip Fracture : Results From The Adventist Health Study-2, Wen-Ling Liao

Loma Linda University Electronic Theses, Dissertations & Projects

This is a two year of follow up study of Adventist Health Study-2 (AHS-2). We assessed the association between physical activity, nutrient intake and risk of hip fracture among peri- and post menopausal Caucasian women using unconditional logistic regression models. All subjects completed a lifestyle questionnaire which including information of physical activity and frequency and portion size of food intake at enrollment into the study (2002-2007). The “Bi-Annual Hospitalization History” questionnaire which included a question about hip fractures due to minor trauma/falls was sent to subjects approximately two years after enrollment, with a response rat of 82.84%. In this cohort, …

Pattern Recognition For Command And Control Data Systems, Jason Schwier

All Dissertations

To analyze real-world events, researchers collect observation data from an underlying process and construct models to represent the observed situation. In this work, we consider issues that affect the construction and usage of a specific type of model. Markov models are commonly used because their combination of discrete states and stochastic transitions is suited to applications with both deterministic and stochastic components. Hidden Markov Models (HMMs) are a class of Markov model commonly used in pattern recognition. We first demonstrate how to construct HMMs using only the observation data, and no a priori information, by extending a previously developed approach …

Integer-Valued Time Series And Renewal Processes, Yunwei Cui

All Dissertations

This research proposes a new but simple model for stationary time series of integer counts. Previous work in the area has focused on mixture and thinning methods and links to classical time series autoregressive moving-average difference equations; in contrast, our methods use a renewal process to generate a correlated sequence of Bernoulli trials. By superpositioning independent copies of such processes, stationary series with binomial, Poisson, geometric, or any other discrete marginal distribution can be readily constructed. The model class proposed is parsimonious, non-Markov, and readily generates series with either short or long memory autocovariances. The model can be fitted with …

A Sequential Algorithm To Identify The Mixing Endpoints In Liquids In Pharmaceutical Applications, Akriti Saxena

Theses and Dissertations

The objective of this thesis is to develop a sequential algorithm to determine accurately and quickly, at which point in time a product is well mixed or reaches a steady state plateau, in terms of the Refractive Index (RI). An algorithm using sequential non-linear model fitting and prediction is proposed. A simulation study representing typical scenarios in a liquid manufacturing process in pharmaceutical industries was performed to evaluate the proposed algorithm. The data simulated included autocorrelated normal errors and used the Gompertz model. A set of 27 different combinations of the parameters of the Gompertz function were considered. The results …

Research On Value-At-Risk In International Crude Oil Shipping Market, Xiaoyin Cui

World Maritime University Dissertations

No abstract provided.

A Study On Opmtimizing The Cold Chain Logistic System In China, Huizhong Chen

World Maritime University Dissertations

No abstract provided.

Research On Decision-Making On Take-Back Models In Reverse Logistics For End-Of-Life Electronic Products, Yiwei Wang

World Maritime University Dissertations

No abstract provided.

The Research On Optimization Of Liner Route Between China To Middle East, Tingyi Chen

World Maritime University Dissertations

No abstract provided.

Development Of Scoring Rubrics And Pre-Service Teachers Ability To Validate Mathematical Proofs, Timothy J. Middleton

Mathematics & Statistics ETDs

The basic aim of this exploratory research study was to determine if a specific instructional strategy, that of developing scoring rubrics within a collaborative classroom setting, could be used to improve pre-service teachers facility with proofs. During the study, which occurred in a course for secondary mathematics teachers, the primary focus was on creating and implementing a scoring rubric, rather than on direct instruction about proofs. In general, the study had very mixed results. Statistically, the quantitative data indicated no significant improvement occurred in participants' ability to validate proofs. However, the qualitative results and the considerable improvement by some participants …