Department of Pure Mathematics and Mathematical Statistics
Centre for Mathematical Sciences
University of Cambridge
Wilberforce Road
Cambridge CB3 0WB
Professor Donald B. Rubin (Harvard).
Stratification for Causal Inference with Extended Partial Compliance
Wolfson Room (MR 2) Tuesday 20 November 2007, 17:00-18:00
Many double-blind placebo-controlled randomized experiments with active
drugs suffer from complications beyond simple noncompliance. First, the
compliance with assigned dose is often partial, with patients taking only
part of the assigned dose, whether active or placebo. Second, the blinding
may be imperfect in the sense that there may be detectable positive or
negative side-effects of the active drug, and consequently, simple
compliance has to be extended to allow different compliances to active
drug and placebo. Efron and Feldman presented an analysis of such a
situation and discussed inference for dose-response from the non-
randomized data in the active treatment arm, which stimulated active
discussion, including concerning the role of the intention-to-treat
principle in such studies. Here, we formulate the problem within the
principal stratification framework of Frangakis and Rubin, which adheres
to the intention-to-treat principle, and we present a new analysis of the
Efron-Feldman data within this framework. Moreover, we describe precise
assumptions under which dose-response can be inferred from such non-
randomized data, which seem debatable in the setting of this example.
Although this article only deals in detail with the specific Efron-Feldman
data, the same framework can be applied to various circumstances in both
natural science and social science.
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