Endgames Statistical Question

Proportional quota sampling

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e6336 (Published 26 September 2012) Cite this as: BMJ 2012;345:e6336
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers assessed the psychological and behavioural reactions of Londoners to the bombings in London on 7 July 2005. A cross sectional telephone survey that used random digit dialling of all London telephone numbers was conducted. Respondents were asked to participate in an interview about current levels of stress and travel intentions. In total, 1010 participants completed the interview. Proportional quota sampling was used to recruit respondents, with quotas based on sex, age, working status, residential location, housing tenure, and ethnicity.1

The main outcome measures were presence of substantial stress and an intention to travel less on public transport once the transport network had returned to normal. The researchers reported that the bombings resulted in substantial stress among 31% of London’s population and altered travel intentions in 32%. Muslims had disproportionately greater levels of stress than respondents from other faiths.

Which of the following does proportional quota sampling represent?

  • a) Non-probability sampling.

  • b) Non-random sampling.

  • c) Probability sampling.

  • d) Random sampling.


Proportional quota sampling is a type of non-random sampling (answer b), sometimes referred to as a non-probability sampling method (answer a).

Proportional quota sampling is often used in …

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