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Biometrics. 1999 Dec;55(4):1286-90.

Adaptive sample size calculations in group sequential trials.

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Institut für Medizinische Statistik, Informatik und Epidemiologie, Universität zu Köln, Germany.


A method for group sequential trials that is based on the inverse normal method for combining the results of the separate stages is proposed. Without exaggerating the Type I error rate, this method enables data-driven sample size reassessments during the course of the study. It uses the stopping boundaries of the classical group sequential tests. Furthermore, exact test procedures may be derived for a wide range of applications. The procedure is compared with the classical designs in terms of power and expected sample size.

[Indexed for MEDLINE]

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