Intended for healthcare professionals

Letters Sample size calculations

Neither off the peg nor made to measure calculations are fit for purpose

BMJ 2012; 345 doi: (Published 02 October 2012) Cite this as: BMJ 2012;345:e6585
  1. Paul D P Pharoah, public health doctor1
  1. 1Strangeways Research Laboratory, University of Cambridge, Cambridge CB1 8RN, UK
  1. paul.pharoah{at}

Norman and colleagues criticise “conventional sample size calculations, based on guesses about statistical parameters” because they “are subject to large uncertainties.” They then propose …

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