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Accounting for informative non‐compliance with a bivariate exponential model in the design of endpoint trials
Author(s) -
Jiang Qi,
Snapinn Steven,
Iglewicz Boris
Publication year - 2005
Publication title -
pharmaceutical statistics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.421
H-Index - 38
eISSN - 1539-1612
pISSN - 1539-1604
DOI - 10.1002/pst.173
Subject(s) - bivariate analysis , sample size determination , econometrics , statistics , equating , compliance (psychology) , range (aeronautics) , sample (material) , computer science , mathematics , psychology , engineering , social psychology , chemistry , chromatography , rasch model , aerospace engineering
Failure to adjust for informative non‐compliance, a common phenomenon in endpoint trials, can lead to a considerably underpowered study. However, standard methods for sample size calculation assume that non‐compliance is non‐informative. One existing method to account for informative non‐compliance, based on a two‐subpopulation model, is limited with respect to the degree of association between the risk of non‐compliance and the risk of a study endpoint that can be modelled, and with respect to the maximum allowable rates of non‐compliance and endpoints. In this paper, we introduce a new method that largely overcomes these limitations. This method is based on a model in which time to non‐compliance and time to endpoint are assumed to follow a bivariate exponential distribution. Parameters of the distribution are obtained by equating them with the study design parameters. The impact of informative non‐compliance is investigated across a wide range of conditions, and the method is illustrated by recalculating the sample size of a published clinical trial. Copyright © 2005 John Wiley & Sons, Ltd.