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Browsing Biostatistics by Title
Now showing items 6-25 of 215
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A method for quantifying the regression to the mean effect applied to bivariate binary outcomes in the presence of limited baseline data
In studies lacking a control group, a crucial step in estimating the study effect is to tease apart the proportion of the total observed change in key outcomes which are due to study participation, from that which is caused ... -
A Novel Analysis of Accelerometry Data: Calibration and Flexible Association Modeling in an Epidemiological Study of Older Women
Accelerometers have been widely deployed to objectively measure and monitor physical activity and sedentary behavior in large epidemiological studies. The traditional summary metric, known as counts, summarizes raw ... -
A Power Transformation-based Compositional Data Analysis Approach with Application to Physical Activity Epidemiology
Compositional data arise in many scientific fields, where relative proportions of different parts of a whole are basic units of data. An example is physical activity (PA) epidemiology, where one is often interested in ... -
A Simpler Model for the Impact of Atrial Fibrillation on Cognitive Trajectories in the Elderly
In their 2013 paper “Atrial fibrillation and cognitive decline: A longitudinal cohort study”, Dr. Thacker and colleagues investigated whether, in the absence of clinical stroke, incident atrial fibrillation was associated ... -
A Simulation Study of Statistical Approaches to Data Analysis in the Stepped Wedge Design
This paper studies model-based and permutation-based approaches to analyze data in the stepped wedge design under 9 scenarios. We compare robustness, efficiency, Type I error rate under null conditions, and power under ... -
A simulation study to evaluate the effect of constrained randomization for the design and analysis of stepped wedge cluster-randomized trials
In this study, we conducted simulations to evaluate the effect of constrained randomization on testing the treatment effect in terms of type I error and power with data generated from a stepped wedge cluster-randomized ... -
A Statistical Method for Analyzing Risk Difference in Trials with a Three-Level Paired Design
This thesis is motivated from an animal trial for a wearable external cardiac defibrillator. Each pig in the trial will be treated with two devices (test vs. control) after induced to experience ventricular fibrillation ... -
A unified approach to model-agnostic variable importance
Assessing the relative contribution of subsets of features towards predicting the response is often of interest in predictive modeling applications; this contribution is typically referred to as variable importance. Often, ... -
Accounting for subject-level heterogeneity in sieve analysis of vaccine efficacy
In randomized trials of preventative vaccines, sieve analysis tests whether vaccine efficacy differs by a characteristic of the disease endpoint. These methods often assume a leaky model, in which treatment proportionally ... -
Accounting for the Presence of Surrogate Data in Adaptive Clinical Trials
Some adaptive designs for randomized clinical trials (RCTs) allow for flexibility in modifying the sequential sampling plan using results from unblinded interim analyses. However, care must be taken to ensure that desired ... -
Adapting Statistical Learning Method for Spatial Applications
In this dissertation, we develop new principled applications of statistical learning methods in spatial applications. In the first chapter, we consider a modified regression tree approach allowing for spatial correlation ... -
Adaptive designs in the time to event setting: The potential for benefit and risk
Group sequential designs (GSDs) have been the standard sequential approach to maintain scientific, ethical, and efficiency goals in any confirmatory Phase III studies. Over the past two decades, adaptive extensions to group ... -
Adaptive Randomization Ratios in Multi-arm Clinical Trials
Ethics and economics are two of many motivations for streamlining the process of discovering new therapies for the treatment of human disease. Population ethics and economics dictate that any true benefit be demonstrated ... -
Adaptive Statistical Inference Procedures for Multigroup Data and Phylogenetic Tree Inferences
Multigroup data is a common data type in fields such as biology, the environmental sciences and the social sciences. This dissertation focuses on developing new statistical methodologies for multigroup data analysis. When ... -
Additive hazards regression with incomplete covariate data
(1997)This dissertation addresses two incomplete covariate data problems in the additive hazards (AH) regression model for failure time data. Both are examples of two-phase designs where some covariate is measured only on a ... -
Addressing Lagged Effects and Interval Censoring in the Stepped Wedge Design of Cluster Randomized Clinical Trials
(2014-02-24)The stepped wedge design (SWD) of cluster-randomized trials has been growing in popularity and is increasingly being used to efficiently evaluate the rollout of interventions in a community setting. The design is especially ... -
Adjusting for Misclassified Outcomes in a Multistate Model
(2013-07-25)In this dissertation, we present a new model that accounts for time-dependent sensitivity in multivariate outcome survival models. Our problem was motivated by an interest in estimating baseline risk and associated covariates ... -
Advances in Model-agnostic Approaches to Statistical Inference
This dissertation focuses broadly on contributing to understanding the impact of incorrect modeling assumptions on analyses and arguing for the use of methods for statistical inference that are valid under weaker conditions ... -
An Empirical Study of Convergence Rates and Resampling-based Confidence Interval Methods For Step Threshold Linear Regression Models
This thesis studies the convergence rates of maximum likelihood estimators and coverage probabilities of resampling-based confidence intervals of parameters in step threshold linear regression models through Monte Carlo ... -
An Evaluation of Flexible Summary Measures for the Comparison of Binary Outcomes in Non-Inferiority Trials
In clinical trials, the comparison of binary outcomes between two independent treatment groups is most commonly measured by either relative or absolute differences between outcome rates. In the setting of a non-inferiority ...