Endgames

Statistical question

Matching

BMJ 2009; 339 doi: 10.1136/bmj.b4581 (Published 11 November 2009)
Cite this as: BMJ 2009;339:b4581

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  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}sgul.ac.uk

    Researchers used a matched case-control study design to investigate whether mobile phone use was associated with the development of glioma, a malignancy of the central nervous system.1 Cases and controls were matched for age and sex. Information about potential risk factors was collected using a self report questionnaire.

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

    • a) Matching reduces assessment bias of the potential risk factors

    • b) Matching adjusts for the effects of age and sex as confounding variables

    • c) Matching eliminates allocation bias

    • d) Matching reduces recall bias

    Answers

    b—In the above study, two groups of individuals were selected on the …

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