Intended for healthcare professionals

Endgames Statistical Question

Random allocation III

BMJ 2009; 339 doi: (Published 03 December 2009) Cite this as: BMJ 2009;339:b5072
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London SW17 0RE
  1. p.sedgwick{at}

    A randomised controlled trial investigated the effectiveness of immobilisation after intrauterine insemination.1 Couples were recruited if the woman needed intrauterine insemination for unexplained subfertility or for subfertility related to cervical factors or male subfertility. A total of 391 couples were recruited from seven teaching hospitals in Holland. Couples were then categorised according to the age of the woman (18-34 or 35-43 years). For each age category at each hospital, couples were randomly allocated either to 15 minutes of immobilisation or immediate mobilisation (control intervention) after intrauterine insemination.


    Which of the following statements, if any, are true?

    • a) Couples were allocated to treatment using stratified random allocation

    • b) Couples were allocated to …

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