Blinded sample size recalculation for clinical trials with normal data and baseline adjusted analysis
Version of Record online: 26 NOV 2009
Copyright © 2009 John Wiley & Sons, Ltd.
Volume 10, Issue 1, pages 8–13, January/February 2011
How to Cite
Friede, T. and Kieser, M. (2011), Blinded sample size recalculation for clinical trials with normal data and baseline adjusted analysis. Pharmaceut. Statist., 10: 8–13. doi: 10.1002/pst.398
- Issue online: 26 NOV 2009
- Version of Record online: 26 NOV 2009
- analysis of covariance;
- baseline variables;
- clinical trials;
- baseline adjustment;
- internal pilot study;
- sample size recalculation
Baseline adjusted analyses are commonly encountered in practice, and regulatory guidelines endorse this practice. Sample size calculations for this kind of analyses require knowledge of the magnitude of nuisance parameters that are usually not given when the results of clinical trials are reported in the literature. It is therefore quite natural to start with a preliminary calculated sample size based on the sparse information available in the planning phase and to re-estimate the value of the nuisance parameters (and with it the sample size) when a portion of the planned number of patients have completed the study. We investigate the characteristics of this internal pilot study design when an analysis of covariance with normally distributed outcome and one random covariate is applied. For this purpose we first assess the accuracy of four approximate sample size formulae within the fixed sample size design. Then the performance of the recalculation procedure with respect to its actual Type I error rate and power characteristics is examined. The results of simulation studies show that this approach has favorable properties with respect to the Type I error rate and power. Together with its simplicity, these features should make it attractive for practical application. Copyright © 2009 John Wiley & Sons, Ltd.