Intended for healthcare professionals

Endgames Statistical Question

Multistage sampling

BMJ 2015; 351 doi: (Published 31 July 2015) Cite this as: BMJ 2015;351:h4155
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Institute for Medical and Biomedical Education, St George’s, University of London, London, UK
  1. Correspondence to: P Sedgwick p.sedgwick{at}

Researchers investigated the views of the British public on the National Cancer Registry’s use of personal medical data for public health research and surveillance without individual consent. A cross sectional study with a face to face survey was performed by the Office for National Statistics. Participants were selected using multistage sampling of adults in the United Kingdom during March and April 2015. In each month a sample of postal districts was selected at random, with the probability of selection proportionate to size. Within each district, a sample of private households was chosen at random. During March 2762 households were selected with a further 1819 households in April. At the start of the interview, the interviewer determined the household composition and selected the respondent from among all those aged 16 or more. In households with more than one adult, one person was selected at random. If the person selected was unavailable or declined to be interviewed it was recorded as a non-response. Face to face interviews were carried out with 1703 (62%) adults in March and 1252 (69%) adults in April. The data were combined for analysis.1

Of the 2955 respondents, 72% (95% confidence interval 70% to 74%) did not consider any of the following to be an invasion of their privacy by the National Cancer Registry: inclusion of postcode, inclusion of name and address, and the receipt of a letter inviting them to a research study …

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