Abstract
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).
Original language | English (US) |
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Pages (from-to) | 211-221 |
Number of pages | 11 |
Journal | Journal of the Royal Statistical Society. Series C: Applied Statistics |
Volume | 56 |
Issue number | 2 |
DOIs | |
State | Published - Mar 2007 |
Keywords
- Causal inference
- Potential outcomes
- Principal stratification
ASJC Scopus subject areas
- Statistics and Probability
- Statistics, Probability and Uncertainty