Abstract #301354

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JSM 2003 Abstract #301354
Activity Number: 133
Type: Contributed
Date/Time: Monday, August 4, 2003 : 12:00 PM to 1:50 PM
Sponsor: Biometrics Section
Abstract - #301354
Title: Estimating Causal Effects in Stratified Randomized Trials with Noncompliance
Author(s): Shigeyuki Matsui*+
Companies: Kyoto University School of Public Health
Address: Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
Keywords: causal effects ; randomization ; stratification ; noncompliance ; efficiency
Abstract:

This paper considers stratified-adjusted analysis in randomized trials with non-compliance. Under the assumption of constant causal effect over strata, an estimating equation is constructed by weighting an unbiased estimating function under randomization from each stratum. When the weights are known, the derived estimator is a natural extension of instrumental variables estimator (e.g., Angrist et al. 1996) to stratified analysis and test-based confidence limits are solutions of a quadratic equation on the causal parameter. The optimal weights which maximize asymptotic efficiency incorporate variability of compliance rates over strata. An assessment-based on asymptotic efficiency shows that analyses using weights that do not incorporate variability of compliance rates over strata, which includes a common intention-to-treat stratified-adjusted test, can incur substantial efficiency loss, compared with analyses with the optimal weights. Application to a field trial for coronary heart disease is given.

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