RAND Statistics Seminar Series

Improving Efficiency of Inferences in Randomized Clinical Trials Using Auxiliary Covariates

Presented by Dr. Marie Davidian, North Carolina State University
Thursday, May 17, 2007
1:30 P.M. EDT
Conference Room 6202
RAND Corporation, Pittsburgh, PA
Please contact Denise Miller if you would like to attend this seminar.


The primary goal of a randomized clinical trial is to make comparisons among two or more treatments. For example, in a two-arm trial with continuous response, the focus may be on the difference in treatment means; with more than two treatments, the comparison may be based on pairwise differences. With binary outcomes, pairwise odds-ratios or log-odds ratios may be used. In general, comparisons may be based on meaningful parameters in a relevant statistical model. Standard analyses for estimation and testing in this context typically are based on the data collected on response and treatment assignment only. In many trials, auxiliary baseline covariate information may also be available, and there has been considerable debate regarding whether and how these data should be used to improve the efficiency of inferences. Taking a semiparametric theory perspective, we propose a broadly-applicable approach to achieving more efficient estimators and tests in the analysis of randomized clinical trials, where “adjustment” for auxiliary covariates is carried out in such a way that concerns over the potential for bias and subjectivity often raised for other covariate adjustment methods may be obviated. Simulations and applications demonstrate the performance of the methods. This is joint work with Anastasios Tsiatis, Min Zhang, and Xiaomin Lu.

Speaker Bio

Dr. Davidian is the William Neal Reynolds Distinguished Professor of Statistics at NCSU and the Executive Editor of the journal Biometrics. She has served in leadership roles in the ASA and the International Biometric Society and on advisory committees for the Food and Drug Administration and the National Institutes of Health. http://www4.stat.ncsu.edu/~davidian/

Attending a Seminar

Other Locations/Times: Washington, D.C. Conf. Rm. 7401: 1:30 p.m. ET
Santa Monica Conf. Rm. 1226 and 1228: 10:30 a.m. PT

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