JSM 2012 Home

JSM 2012 Online Program

The views expressed here are those of the individual authors and not necessarily those of the JSM sponsors, their officers, or their staff.

Online Program Home

Abstract Details

Activity Number: 469
Type: Contributed
Date/Time: Wednesday, August 1, 2012 : 8:30 AM to 10:20 AM
Sponsor: Biometrics Section
Abstract - #306383
Title: Models for a Longitudinal Quantitative Outcome with Multivariate Normal (MVN) Distribution Censored by Therapeutic Intervention
Author(s): Wanjie Sun*+ and Michael D. Larsen and John M. Lachin
Companies: The George Washington University and The George Washington University and The George Washington University
Address: 6110 Executive Blvd, Rockville, MD, 20852-3903, United States
Keywords: Multiple imputation ; Monte Carlo EM ; Censored Normal Regression ; Truncated MVN

In longitudinal clinical trials, epidemiologic, or genetic studies, a quantitative outcome may be altered by the administration of a non-randomized, non-trial intervention during follow up. The re- sulting effect of the non-trial intervention may seriously bias the study results, including treatment or exposure effects or associations. Current methods to address this issue including multilevel models (White et al 2001) or multiple imputation (MI) (Cook 1997, Cook 2006), are either restricted to a specific longitudinal data structure or are valid only under special circumstances. We propose two new methods for general longitudinal data - a modified Expectation-Maximization (EM)-type model and a modified Monte Carlo EM-MI model. These combine Monte Carlo EM (Wei and Tanner 1990) and MI, and are extensions of Censored Normal Regression (Tobin et al 2005) to longitudinal data. These replace the intractable calculation of a multi-dimensionally truncated MVN posterior distribution with a simplified but sufficiently accurate approximation. Simulation shows that the two proposed methods have the least biased treatment effect estimate in a majority of simulated scenarios amongst six methods applied.

The address information is for the authors that have a + after their name.
Authors who are presenting talks have a * after their name.

Back to the full JSM 2012 program

2012 JSM Online Program Home

For information, contact jsm@amstat.org or phone (888) 231-3473.

If you have questions about the Continuing Education program, please contact the Education Department.