Interim analysis: the alpha spending function approach

Stat Med. 1994 Jul;13(13-14):1341-52; discussion 1353-6. doi: 10.1002/sim.4780131308.


Interim analysis of accumulating data in a clinical trial is now an established practice for ethical and scientific reasons. Repeatedly testing interim data can inflate false positive error rates if not handled appropriately. Group sequential methods are a commonly used frequentist approach to control this error rate. Motivated by experience of clinical trials, the alpha spending function is one way to implement group sequential boundaries that control the type I error rate while allowing flexibility in how many interim analyses are to be conducted and at what times. In this paper, we review the alpha spending function approach, and detail its applicability to a variety of commonly used statistical procedures, including survival and longitudinal methods.

MeSH terms

  • Bias
  • Clinical Trials as Topic / statistics & numerical data*
  • Data Interpretation, Statistical*
  • Double-Blind Method
  • Humans
  • Longitudinal Studies
  • Multicenter Studies as Topic
  • Myocardial Infarction / drug therapy
  • Myocardial Infarction / mortality
  • Propranolol / therapeutic use
  • Randomized Controlled Trials as Topic / statistics & numerical data
  • Survival Analysis


  • Propranolol