Group sequential procedures for repeated events data with frailty

W. Jiang*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

8 Scopus citations


In this article we consider the design aspects of group sequential trials with recurrent study endpoints, where the subjects are from a heterogeneous population. The usual procedures of sequential analysis based on the 'independent increments' property are no longer valid due to the heterogeneity of the study subjects, as pointed out by Cook and Lawless (1). We focus on the aspect of study planning and consider a special model (Poisson process with frailty) to investigate the effects of frailty (or subject heterogeneity). We prescribe the valid procedures and provide convenient tables for computing stopping boundaries and sample sizes. The methodology is illustrated through an example of an animal experiment with recurrent tumors, using procedures such as group sequential tests and repeated confidence intervals. Minimal cost analysis is considered for determining the optimal combination of study duration and sample size.

Original languageEnglish (US)
Pages (from-to)379-399
Number of pages21
JournalJournal of Biopharmaceutical Statistics
Issue number3
StatePublished - 1999


  • Frailty
  • Independent increments
  • Interim analyses
  • Minimal cost analysis
  • Multiplicative intensity model
  • Poisson process
  • Recurrent events

ASJC Scopus subject areas

  • Statistics and Probability
  • Pharmacology
  • Pharmacology (medical)


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