Biostatistics
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Evaluating prediction performance of longitudinal biomarkers under cohort and twophase study designs
Risk prediction and evaluation of predictions based on longitudinal biomarkers are of interest in treatment selection, preventive medicine and management of chronic diseases. Methods to evaluate risk predictions in a ... 
New methods for metaanalysis under a fixed effects framework, with frequentist and Bayesian estimation.
Metaanalysis, as a pivotal component of systematic reviews, has been used extensively in recent years to synthesize the increasing amount of evidence produced in medical and health care research. The two main approaches ... 
Graph Estimation and Cluster Analysis in High Dimensions
In many applications, it is of interest to uncover patterns from a highdimensional data set in which the number of features, p, is larger than the number of observations, n. We consider the areas of graph estimation and ... 
Methods for describing the timevarying predictive performance of survival models
In this dissertation we develop new methods for quantifying the predictive performance of a survival model at different times. We broadly categorize predictive performance into either calibration or discrimination, and ... 
A more powerful quasilikelihood score test for detecting genetic association with multivariate phenotypes in related samples
Pleiotropy is a commonly observed phenomenon in human genetics where a single gene influences multiple, and sometimes seemingly unrelated traits. Recently there has been significant interest in the identification of genetic ... 
Stochastic Optimization and Subgroup Selection
An important area in statistics is that of experimental or study design. The most typical problem is that of finding the required sample size that meets specific goals such as controlling type I and II error rates at given ... 
Adaptive Randomization Ratios in Multiarm 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 ... 
Inferring Biological Networks from TimeCourse Observations Using a Nonlinear Vector Autoregressive Model
Cellular functions are increasingly viewed as being regulated through networks of molecules working in parallel. Discovery and characterization of these networks is fundamental to understanding diseases and developing ... 
Joint modeling of survival and longitudinal data measured with error, with application to assessing immune correlates of protection in vaccine efficacy trials
Assessing immune correlates of protection, the immune responses that reliably predict the vaccine efficacy on the clinical endpoint, has always been an important objective in vaccine efficacy trials. In this dissertation, ... 
A Zestimation System for Twophase Sampling with Applications to Additive Hazards Models and Epidemiologic Studies
An observational epidemiologic study often follows a large amount of participants for occurrence of diseases. If every covariate is measured for every participant, then the study can be highly expensive. Twophase ... 
Inferring, Estimating, and Accounting for Population and Pedigree Structure in Genetic Analyses
Genetic studies of admixed individuals with ancestry derived from multiple previously isolated populations have become more common in recent years. Statistical methodology for analyzing genetic data in the presence of ... 
Methods for the prediction of endpointoccurrence times in clinical trials
This research is motivated by the need to anticipate the calendar time of landmark numbers of events in a clinical trial with a timetoevent monitoring endpoint. In such trials, the observed number of events usually ... 
Unconditional Exact Tests for Binomial Proportions in the Group Sequential Setting
Exact inference for independent binomial outcomes in small samples is complicated by the presence of a meanvariance relationship that depends on nuisance parameters, discreteness of the outcome space, and departures from ... 
Biostatistical Methods for HIV Monitoring and Prevention
Part I Pooledtesting methods can greatly reduce the number of tests needed to identify failures in a collection of samples. Existing methodology has focused primarily on binary tests, but there is a clear need for improved ... 
Estimation and Conditional Inference in HighDimensional Statistical Models
In many areas of biology, recent advances in technology have facilitated the measurement of large numbers of features, while the number of observations in a data set may remain relatively modest. In this setting, lasso ... 
Smoking and CVD in the MultiEthnic Study of Atherosclerosis: Functional Form, Mediating Pathways, and Implications of Intensity Reduction
Smoking as an epidemiological exposure can be quantified in terms of duration, intensity, packyears, recency, and time of life. It is not clear which of these are important for cardiovascular disease, and how they should ... 
Causal mediation analysis with failure time outcome and errorprone 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 ... 
Bayesian Hierarchical Frailty Models for Heterogeneity in Risk
The effect of an intervention or exposure on timetoevent is most commonly estimated with the Cox model, which assumes proportional hazards. When heterogeneity in risk is present, the assumption of proportionality is ... 
Spatial measurement error methods in air pollution epidemiology
Air pollution epidemiology cohort studies often implement a twostage approach to estimating associations of continuous health outcomes with one or more exposures. An inherent problem in these studies is that the exposures ... 
A Marginal Structural Cox Model Based Analysis Of The Comparative Effectiveness Of Two Dialysis Therapies
The Institute of Medicine identified comparing the effectiveness of renal replacement therapies as the only kidneydisease related topic among the top 100 initial national priorities for comparative effectiveness research. ...