Home > Publications . Search All . Browse All . Country . Browse PSC Pubs . PSC Report Series

PSC In The News

RSS Feed icon

Buchmueller says employee wages are hit harder than corporate profits by rising health insurance costs

Davis-Kean et al. link children's self-perceptions to their math and reading achievement

Yang and Mahajan examine how hurricanes impact migration to the US

More News


Pamela Smock elected to PAA Committee on Publications

Viewing the eclipse from ISR-Thompson

Paula Fomby to succeed Jennifer Barber as Associate Director of PSC

PSC community celebrates Violet Elder's retirement from PSC

More Highlights

Next Brown Bag

Mon, Sept 11, 2017, noon:
Welcoming of Postdoctoral Fellows: Angela Bruns, Karra Greenberg, Sarah Seelye and Emily Treleaven

Mediation analysis with principal stratification

Publication Abstract

Gallop, Robert, Dylan S. Small, Julia Y. Lin, Michael R. Elliott, Marshall Joffe, and Thomas R. Ten Have. 2009. "Mediation analysis with principal stratification." Statistics in Medicine, 28(7): 1108-1130.

In assessing the mechanism of treatment efficacy in randomized clinical trials, investigators often perform mediation analyses by analyzing if the significant intent-to-treat treatment effect on outcome occurs through or around a third intermediate or mediating variable: indirect and direct effects, respectively. Standard mediation analyses assume sequential ignorability, i.e. conditional on covariates the intermediate or mediating factor is randomly assigned, as is the treatment in a randomized clinical trial. This research focuses on the application of the principal stratification (PS) approach for estimating the direct effect of a randomized treatment but without the standard sequential ignorability assumption. This approach is used to estimate the direct effect of treatment as a difference between expectations of potential outcomes within latent subgroups of participants for whom the intermediate variable behavior would be constant, regardless of the randomized treatment assignment. Using a Bayesian estimation procedure, we also assess the sensitivity of results based on the PS approach to heterogeneity of the variances among these principal strata. We assess this approach with simulations and apply it to two psychiatric examples. Both examples and the simulations indicated robustness of our findings to the homogeneous variance assumption. However, simulations showed that the magnitude of treatment effects derived under the PS approach were sensitive to model mis-specification.

DOI:10.1002/sim.3533 (Full Text)

PMCID: PMC2669107. (Pub Med Central)

Browse | Search : All Pubs | Next