Seminars and Invited Talks



Mar 31, 2017 Sujit K. Ghosh, Ph.D.

Department of Statistics
North Carolina State University
Raleigh, NC

When are PH, AFT and PO models not adequate for regression with censored responses?

In many clinical applications of survival analysis with covariates, the commonly used semiparametric models, e.g., proportional hazards (PH), proportional odds (PO), accelerated failure time (AFT) etc. may turn out to be stringent and unrealistic, particularly when there is scientific background to believe that survival curves under different covariate combinations will cross during the study period. This talk presents a relatively new class of nonparametric regression model for the conditional hazard function. The new methodology has three key features: (i) the smooth estimator of the conditional hazard rate is shown to be a unique solution of a strictly convex optimization problem for a wide range of applications; making it computationally attractive, (ii) the model is shown to encompass a proportional hazards structure, and (iii) large sample properties including consistency and convergence rates are established under a set of mild regularity conditions. Empirical results based on several simulated data scenarios indicate that the proposed model has reasonably robust performance compared to other semiparametric models particularly when such semiparametric modeling assumptions are violated.

One Capitol Square
Room 305

Apr 7, 2017 Wenbin Lu, Ph.D.

Department of Statistics
North Carolina State University
Raleigh, NC

Maximin-Projection Learning for Optimal Treatment Decision with Heterogeneous Data

Large medical data collected from clinical trials and observational studies often exhibit heterogeneity due to various reasons, such as difference in geographical locations as commonly seen in multi-center studies. Due to the heterogeneity in data, the optimal treatment decision might vary across patients from different study populations. As such, it becomes crucial to appropriately account for data heterogeneity when deriving the optimal treatment regime for achieving the best clinical outcome of interest. In this work, we propose a novel maximin-projection learning for estimating a single treatment decision rule that works reliably for patients across different subgroups. Based on the estimated optimal treatment regime for all subgroups, the proposed maximin treatment regime is obtained by solving a quadratically constrained linear programming (QCLP) problem, which can be efficiently computed by the interior-point method. Consistency and asymptotic normality of the estimator are established. Numerical examples show the reliability and effectiveness of the proposed methodology.

One Capitol Square
Room 305

Apr 11, 2017 Bhanu M. Evani, M.S.

Ph.D. Candidate
Department of Biostatistics
Virginia Commonwealth University

Public Portion of the Final Defense

Weighted Quantile Sum Regression for Analyzing Correlated Predictors Acting through a Mediation Pathway on a Biological Outcome

This work examines mediated effects of a set of correlated predictors using the recently developed Weighted Quantile Sum (WQS) regression method. Traditionally, mediation analysis has been conducted using the multiple regression method, first proposed by Baron and Kenny (1986), which has since been advanced by several authors like MacKinnon (2008).

Mediation analysis of a highly correlated predictor set is challenging due to the condition of multicollinearity. Weighted Quantile Sum (WQS) regression can be used as an alternative method to analyze the mediated effects when predictor correlations are high. As part of the WQS method, a weighted quartile sum index (WQSindex) is computed to represent the predictor set as an entity. The predictor variables in classic mediation are then replaced with the WQSindex, allowing for the estimation of the total indirect effect between all the predictors and the outcome. Predictors having a high relative importance in their association with the outcome can be identified by examining the empirical weights for the individual predictors, estimated by the WQS regression method. Other constrained optimization methods (e.g. LASSO) focus on reducing dimensionality of the correlated predictors to reduce multicollinearity.

WQS regression in the context of mediation is studied using Monte Carlo simulation for mediation models with two and three correlated predictors. WQS regression’s performance is compared to the classic OLS multiple regression and the regularized LASSO regression methods. An application of these three methods to the National Health and Nutrition Examination Survey (NHANES) dataset examines the effect of serum concentrations of Polychlorinated Biphenyls (independent variables) on the liver enzyme, alanine aminotransferase ALT (outcome), with chromosomal telomere length as a potential mediator.

1:00 p.m.
One Capitol Square
12th Floor Conference Room

Apr 14, 2017 Lukasz Kurgan, Ph.D.

Department of Computer Science
Virginia Commonwealth University

One Capitol Square
Room 305

Apr 28, 2017 Snigdhanshu Chatterjee, Ph.D.

Associate Professor
Department of Statistics
University of Minnesota

One Capitol Square
Room 305

Previous Seminars

Mar 24, 2017 Stacia M. DeSantis, Ph.D.
Mar 10, 2017 Casey S. Greene, Ph.D.
Mar 3, 2017 POSTPONED: Tingting Zhang, Ph.D.
Feb 24, 2017 Montserrat Fuentes, Ph.D.
Feb 17, 2017 Samiran Sinha, Ph.D.
Feb 10, 2017 Xin (Cynthia) Tong, Ph.D.
Jan 27, 2017 Codruta Chiuzan, Ph.D.
Dec 2, 2016 Chao Du, Ph.D.
Nov 18, 2016 Hongkun Wang, Ph.D.
Nov 16, 2016 Kyle L. Ferber
Nov 11, 2016 Yanxun Xu, Ph.D.
Nov 10, 2016 Emily V. Dressler, Ph.D.
Nov 4, 2016 Mikhail Dozmorov, Ph.D.
Nov 3, 2016 Arindam RoyChoudhury, Ph.D.
Oct 28, 2016 Aaron Quinlan, Ph.D.
Oct 21, 2016 Bruce Swihart, Ph.D.
Oct 14, 2016 Bo Cai, Ph.D.
Oct 7, 2016 Helen Wang, M.S.
Sep 23, 2016 Cheng Ly, Ph.D.
Sep 16, 2016 Xiaowei Wu, Ph.D.
Sep 9, 2016 Brian J. Reich, Ph.D.
Aug 25, 2016 Vanda Inacio, Ph.D.
Aug 22, 2016 Hui Wang
Aug 18, 2016 Student Research Symposium
Jul 29, 2016 Kabita Joshi, MPH, M.S.
Jul 22, 2016 Edmund R. Glass
May 6, 2016 Jianlin Cheng, Ph.D.
May 4, 2016 Jenna N. Czarnota
Apr 29, 2016 Eric Vance, Ph.D.
Apr 28, 2016 Lauren P. Grant
Apr 27, 2016 Aobo Wang
Apr 26, 2016 Qing Zhou
Apr 22, 2016 Jenise L. Swall, Ph.D.
Apr 15, 2016 Jay Mandrekar, Ph.D.
Apr 8, 2016 Tom Arodz, Ph.D.
Apr 1, 2016 Jacob Wegelin, Ph.D.
Mar 25, 2016 Frank W. Rockhold, Ph.D.
Feb 12, 2016 Linda Corey, Ph.D.
Jan 29, 2016 Mikhail Dozmorov, Ph.D.
Dec 4, 2015 Timothy York, Ph.D.
Dec 2, 2015 Uma Siangphoe
Nov 20, 2015 Tamas S. Gal, Ph.D.
Nov 13, 2015 Dongjun Chung, Ph.D.
Nov 9, 2015 Andrey Afanasyev
Nov 5, 2015 Frank Harrell, Ph.D.
Oct 28, 2015 Helen Wang, M.S.
Oct 23, 2015 Andrey Rzhetsky, Ph.D.
Oct 9, 2015 Dong-Yun Kim, Ph.D.
Oct 2, 2015 CANCELLED: Helen Wang, M.S.
Sep 18, 2015 Rui Feng, Ph.D.
Aug 21, 2015 Student Research Symposium
Jul 22, 2015 Mateusz Makowski
May 27, 2015 Shanshan Chen, Ph.D.
Apr 24, 2015 Hadiza I. Galadima
Apr 17, 2015 Alicia Y. Toledano, Sc.D.
Apr 10, 2015 CANCELLED: Gregory Buck, Ph.D.
Apr 3, 2015 Julian Rosenman, Ph.D., M.D.
Mar 27, 2015 Dipankar Bandyopadhyay, Ph.D.
Mar 20, 2015 Bridget Thomson-McInnes, Ph.D.
Mar 13, 2015 Chi Song, Ph.D.
Mar 6, 2015 Guofen Yan, Ph.D.
Feb 27, 2015 Michael R. Kosorok, Ph.D.
Feb 13, 2015 Minsun Song, Ph.D.
Feb 6, 2015 Hua He, Ph.D.
Dec 5, 2014 Levent Dumenci, Ph.D.
Nov 25, 2014 Paul T. Manser, M.S.
Nov 21, 2014 Andriy Bandos, Ph.D.
Nov 14, 2014 RESCHEDULED – Levent Dumenci, Ph.D.
Oct 30, 2014 Mary E. Haynes
Oct 10, 2014 Wei Zhang, Ph.D.
Sep 26, 2014 Max Kuhn, Ph.D.
Sep 12, 2014 Frank Samuelson, Ph.D. and David Brown, Ph.D.
Sep 5, 2014 Biostatistics Student Research Symposium Program
Aug 29, 2014 Biostatistics Student Research Symposium Program
Jul 24, 2014 Xiangrong Kong, Ph.D.
Jul 18, 2014 Ying Liu, Ph.D.
Jul 14, 2014 Bo Zhang, Ph.D.
Jun 2, 2014 Chunfeng Ren, M.S., M.P.H.
Apr 30, 2014 Department Graduation Ceremony
Apr 25, 2014 Joan E. Bailey-Wilson, Ph.D.
Apr 21, 2014 Ghalib Bello
Apr 18, 2014 Pam R. Factor-Litvak, Ph.D.
Naha Farhat
Apr 11, 2014 Capt. Katherine A. Batterton
Apr 4, 2014 Scarlett L. Bellamy, Sc.D.
Mar 21, 2014 Yang Feng, Ph.D.
Mar 7, 2014 Qingguo Wang, Ph.D.
Feb 28, 2014 Mikhail Dozmorov, Ph.D.
Feb 21, 2014 Justine Shults, Ph.D.
Feb 14, 2014 Summer Student Training Program Presentations
Feb 7, 2014 Zhe Zhang
Jan 27, 2014 David Fenstermacher, Ph.D.
Jan 24, 2014 CANCELLED: Susan Parker, Ph.D.
Jan 17, 2014 Mark Reimers, Ph.D.
Nov 25, 2013 Jiayi Hou
Nov 22, 2013 Hanan Hammouri, M.S.
Nov 18, 2013 Shuxian Sinks
Nov 15, 2013 George Ostrouchov, Ph.D.
Nov 8, 2013 Qin Wang, Ph.D.
Oct 25, 2013 CANCELLED: Shanna Swan, Ph.D.
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