Adaptive Sample Size Calculations in Group Sequential Trials

Authors

  • Walter Lehmacher,

    Corresponding author
    1. Institut für Medizinische Statistik, Informatik und Epidemiologie, Universität zu Köln, Joseph-Stelzmann-Str. 9, D-5Q931 Köln, Germany
    Search for more papers by this author
  • Gernot Wassmer

    1. Institut für Medizinische Statistik, Informatik und Epidemiologie, Universität zu Köln, Joseph-Stelzmann-Str. 9, D-5Q931 Köln, Germany
    Search for more papers by this author

*email:walter.lehmacher@medizin.uni-koeln.de

Abstract

Summary. 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.

Ancillary