Unbiased estimation of selected treatment means in two-stage trials

Jack Bowden*, Ekkehard Glimm

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

68 Citations (Scopus)


Straightforward estimation of a treatment's effect in an adaptive clinical trial can be severely hindered when it has been chosen from a larger group of potential candidates. This is because selection mechanisms that condition on the rank order of treatment statistics introduce bias. Nevertheless, designs of this sort are seen as a practical and efficient way to fast track the most promising compounds in drug development. In this paper we extend the method of Cohen and Sackrowitz (1989) who proposed a two-stage unbiased estimate for the best performing treatment at interim. This enables their estimate to work for unequal stage one and two sample sizes, and also when the quantity of interest is the best, second best, or j-th best treatment out of k. The implications of this new flexibility are explored via simulation.

Original languageEnglish
Pages (from-to)515-527
Number of pages13
JournalBiometrical Journal
Issue number4
Publication statusPublished - 1 Aug 2008


  • Adaptive trial
  • Point estimation
  • Selection bias


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