title: Adaptive sample size calculations in group sequential trials.
abstract: 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.
authors: Institut für Medizinische Statistik, Informatik und Epidemiologie, Universität zu Köln, Germany. walter.lehmacher@medizin.uni-koeln.de
authors: W
authors: W
authors: Lehmacher
authors: G
authors: G
authors: Wassmer
mesh_terms: D000152:Acne Vulgaris / Q000188:drug therapy / Q000382:microbiology; D001699:Biometry; D002701:Chloramphenicol / Q000008:administration & dosage; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data*; D015169:Colony Count, Microbial; D016001:Confidence Intervals; D006801:Humans; D015233:Models, Statistical; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D018401:Sample Size
chemical_list: D002701:Chloramphenicol