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Endgames Statistical Question

Study design

BMJ 2009; 339 doi: (Published 05 November 2009) Cite this as: BMJ 2009;339:b4458
  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}

    To investigate whether physical activity in preschool children (under 5 years) reduced obesity, researchers recruited 545 children from 36 preschool nurseries. Each nursery was randomly allocated to an enhanced physical activity programme plus health education or no intervention (control group). The body mass, physical activity, and sedentary behaviour of each child in each nursery was recorded at regular intervals for 12 months.1

    Which one of the following study designs best describes that used in the above study?

    • a) Case-control study

    • b) Double blind randomised controlled trial

    • c) Cluster randomised controlled trial

    • d) Nested case-control study


    c—In a cluster randomised …

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