Healthy Skepticism Library item: 17263

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Publication type: Journal Article

Sleight P
Debate: Subgroup analyses in clinical trials: fun to look at - but don't believe them!
Current Controlled Trials in Cardiovascular Medicine 2000 July 31; 1:(1):25-27
http://trialsjournal.com/content/1/1/25

Abstract:

Analysis of subgroup results in a clinical trial is surprisingly unreliable, even in a large trial. This is the result of a combination of reduced statistical power, increased variance and the play of chance. Reliance on such analyses is likely to be more erroneous, and hence harmful, than application of the overall proportional (or relative) result in the whole trial to the estimate of absolute risk in that subgroup. Plausible explanations can usually be found for effects that are, in reality, simply due to the play of chance. When clinicians believe such subgroup analyses, there is a real danger of harm to the individual patient.

Keywords:
astrology, clinical trials, overview, play of chance, randomization