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Table 5 Approach to multiplicity due to interim analyses

From: Approaches to multiplicity in publicly funded pragmatic randomised controlled trials: a survey of clinical trials units and a rapid review of published trials

a) Review: approach taken to multiplicity
  Formal adjustment Hierarchical testing Other approach None
Interim analyses 26/41a (63%) 0/41 (0%) 2/41b (5%) 13/41c (32%)
b) Survey: responses to posed scenarios
  Always Sometimes Never Unsure
Would you adjust for multiplicity if interim analysis(es) were pre-specified in the study protocol? 8/27 (30%) 12/27 (44%) 3/27 (11%) 4/27 (15%)
  1. Notes: a Eight trials used the Haybittle-Peto procedure, eight used O’Brien-Fleming, seven partitioned the significance level between final and interim analyses (with no further details given), one used Pocock, one used Lan DeMets and one did not give details.
  2. bOne trial used a group sequential design and one used a conditional rejection probability approach.
  3. cOf these, three trials stated a pre-specified significance level for stopping the trial.