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Estimating Efficacy in a Proposed Randomized Trial with Initial and Later Non-Compliance
Stuart G. Baker, Constantine Frangakis and Karen S. Lindeman
Journal of the Royal Statistical Society. Series C (Applied Statistics)
Vol. 56, No. 2 (2007), pp. 211-221
Stable URL: http://www.jstor.org/stable/4626762
Page Count: 11
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A controversial topic in obstetrics is the effect of walking on the probability of Caesarean section among women in labour. A major reason for the controversy is the presence of non-compliance that complicates the estimation of efficacy, the effect of treatment received on outcome. The intent-to-treat method does not estimate efficacy, and estimates of efficacy that are based directly on treatment received may be biased because they are not protected by randomization. However, when non-compliance occurs immediately after randomization, the use of a potential outcomes model with reasonable assumptions has made it possible to estimate efficacy and still to retain the benefits of randomization to avoid selection bias. In this obstetrics application, non-compliance occurs initially and later in one arm. Consequently some parameters cannot be uniquely estimated without making strong assumptions. This difficulty is circumvented by a new study design involving an additional randomization group and a novel potential outcomes model (principal stratification).
Journal of the Royal Statistical Society. Series C (Applied Statistics) © 2007 Royal Statistical Society