Letters

Placebo controlled trials are needed to provide data on effectiveness of active treatment

BMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7063.1008b (Published 19 October 1996) Cite this as: BMJ 1996;313:1008
  1. D B Double, Consultant psychiatrist
  1. Southeast Sheffield Mental Health Services, Sheffield S12 4QN

    EDITOR,—Kenneth J Rothman questions whether there is any point in using a placebo group if blind assessment can be achieved in a comparative trial of two active treatments.1 He minimises both the practical advantages of placebo controlled trials and their advantages for hypothesis testing. The limitations of statistical hypothesis testing mean that the probability of an inferential error is known if one is rejecting the null hypothesis but not if one is accepting it.2 The probability of a type II error in equivalence …

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