Browsing Biostatistics by Title
Now showing items 45-64 of 215
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Causal inference in HIV vaccine trials: comparing outcomes in a subset chosen after randomization
(2005)In many experiments researchers would like to compare between treatments an outcome that only exists in a subset of participants selected after randomization. For example, in preventative HIV vaccine efficacy trials it is ... -
Causal Inference with Selection and Confounding Variables
Most complex observational and randomized studies are motivated by the potential of drawing causal statements. However, a usual statistical analysis may yield estimates that do not have causal interpretations. In fact, ... -
Causal mediation analysis with failure time outcome and error-prone longitudinal covariate
Mediation analyses are important for understanding the biological mechanisms whereby a treatment/exposure influences an outcome of interest. For example, one may be interested in whether body fat accumulation mediates an ... -
Challenges Associated with Statistical Analysis in the Presence of Sparse Data and Applications to Alternative Tobacco Product Research
(2013-07-23)Rarely observed covariate combinations, or "sparsity" is a phenomenon associated with research concerning the health risks of alternative-use (non-combusted tobacco products (AUPs)). Of particular concern is sparsity ... -
Combining Biomarkers for Diagnosis, Prognosis, and Screening: Methods for Direct Maximization, Multilevel Outcomes, and Multicenter Studies
Interest in using biomarkers for prognosis, diagnosis, and screening continues to grow in many clinical areas. However, most biomarkers have only modest predictive capacity and therefore are not clinically useful. As the ... -
Combining Survey and Census Data in Time and Space in a Developing World Context
Obtaining reliable estimates of health indicators at a granular level in space and time is important for informing health intervention and public policy decisions. In low and middle income countries, the data available ... -
Comparing Internal Validation Methods for a Random Forest Prediction Model of Suicide Death
Predictive models estimated with clinical data are increasingly popular in the medical data field. After developing a prediction model, its necessary to evaluate its performance in practice, or validate the model. Model ... -
A Comparison of Sample Size Calculations for Cluster Randomized Crossover Trials with a Binary Outcome
A simplified sample size calculation for a cluster randomized crossover trial with a binary survival outcome (the “ T-BOSS ” method) was compared to the closed form equation and simulation methods currently available from ... -
Comparison of Several Statistical Tests for Evaluating Novel Treatments in the Out-of-Hospital Cardiac Arrest Setting
In the out-of-hospital cardiac arrest (OHCA) setting, it is generally agreed that a clinically meaningful endpoint, such as survival with neurological and physiological status similar to pre arrest, is a good outcome. For ... -
A comparison of three trough to peak estimators derived from ambulatory blood pressure data
(1997)A general multivariate model is proposed to analyze ABPM data obtained from multiple subjects in which two ABPM series, typically at baseline and on randomized therapy in a clinical trial, are obtained on each subject. The ... -
Covariate Measurement Error Correction Methods in Mediation Analysis with Failure Time Data
(2013-04-17)Mediation analysis is important in understanding the mechanisms of one variable causing changes in another. Measurement error could be obscuring the ability of the potential mediator to explain this mechanism. Existing ... -
Covariate-specific Breakpoints in Personalized Evaluation of Left Ventricular Enlargement
In this thesis, we outline a flexible and interpretable iterative method to fit generalized segmented linear models with covariate-specific breakpoints and evaluate its statistical performance by conducting simulation ... -
Data-adaptive Estimation in Longitudinal Data Structures with Applications in Vaccine Efficacy Trials
This dissertation develops methodology for data-adaptive estimation of parameters defined on longitudinal data structures, while this abstract serves as an introduction to the material covered herein. The dissertation is ... -
Data-Adaptive Modeling using Convex Regression
The collection and storage of large amounts of data has greatly increased in recent years, which has led to a greater interest in developing methods to explore and model this data. In settings in which little is known about ... -
Dimension Reduction for Spatially-Misaligned and Multi-Pollutant Data with Missing Observations
Accurate predictions of pollutant concentrations at new locations are often of interest in air pollution studies, in which data are usually not measured at all study locations. Ambient air is also a mixture of many chemical ... -
Disequilibrium fine-mapping of a rare allele via coalescent models of gene ancestry
(1998)Genetic linkage studies based on pedigree data have limited resolution, due to the relatively small number of segregations. Disequilibrium mapping, which uses population associations to infer the location of a disease ... -
Distribution-Free Approaches to Assessing the Potential Clinical Impact of Biomarkers
Recent advances in basic science, combined with new technologies that enable measurement of sophisticated biological processes, present numerous opportunities for advancing the clinical care of patients. A basic tenet of ... -
Effect of Time Measurement Error on Assessing Treatments with Time Dependent Effect
In the emergency medicine setting, it is often difficult to accurately record the time of injury without measurement error. If the treatment effect varies depending on the time from injury to treatment initiation, this ... -
Effects of HAART and Time on the Beta Diversity of Breast Milk Microbiome in HIV-infected Postpartum Women
Introduction - Highly active antiretroviral therapy (HAART) has been used in HIV-infected pregnant women to suppress viral replication and reduce perinatal transmission. However, the influence of HAART on the breast milk ... -
Efficient Estimation Under Data Fusion
This dissertation introduced a general framework and approach for researchers to tackle data fusion problems in generality. The following three chapters contribute to a cohesive narrative, wherein each chapter addresses a ...