Endgames Statistical question

Response rates to surveys

BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a3094 (Published 30 December 2008) Cite this as: BMJ 2008;337:a3094
  1. John Fletcher, clinical epidemiologist
  1. 1BMJ, London WC1H 9JR
  1. jfletcher@bmj.com

    A survey was conducted in a maternity unit to estimate the prevalence of the use of marijuana during pregnancy. Five hundred women were surveyed and questionnaires were received back from 250. Which, if any, of these statements are true?

    • a Selection bias may be reduced by increasing the sample size

    • b If women answer truthfully then the results will not be biased

    • c If women …

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