A group sequential t-test with updating of sample size

Jonathan S. Denne, Christopher Jennison

Research output: Contribution to journalArticlepeer-review

32 Citations (SciVal)


If the maximum sample size for a group sequential t-test is calculated on the basis of a prior estimate of the variance, power at a fixed distance from the null hypothesis is not robust to misspecification of the variance. We propose a new group sequential t-test, based on Stein's (1945) two-stage test, in which we use internal estimates of the variance to update the maximum sample size, and allow early stopping to reject the null hypothesis through a Lan & DeMets (1983) error-spending function. We evaluate our procedure's performance and show that it closely controls the type I and II error rates.

Original languageEnglish
Pages (from-to)125-134
Number of pages10
Issue number1
Publication statusPublished - 2000

Bibliographical note

Copyright 2017 Elsevier B.V., All rights reserved.


  • Clinical trial
  • Error-spending function
  • Group sequential test
  • Interim monitoring
  • Internal pilot
  • Resizing
  • Sample size calculation
  • T-test
  • Unknown variance

ASJC Scopus subject areas

  • Statistics and Probability
  • General Mathematics
  • Agricultural and Biological Sciences (miscellaneous)
  • General Agricultural and Biological Sciences
  • Statistics, Probability and Uncertainty
  • Applied Mathematics


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