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Ethnicity and analgesia in accident departments

BMJ 2000; 321 doi: (Published 19 August 2000) Cite this as: BMJ 2000;321:513

Authors did not exclude type II error or perform power calculation

  1. Peter Leman (, accident and emergency consultant
  1. St Thomas's Hospital, London SE1 7EH
  2. Barts and the London NHS Trust, Department of Anaesthetics, Royal London Hospital, London E1 1BB
  3. Clinical Effectiveness Unit, Royal London Hospital
  4. St Bartholomew's and the Royal London School of Medicine and Dentistry, Department of Environmental and Preventive Medicine, London E1 2AD

    EDITOR—Choi et al investigated whether ethnicity had any bearing on the prescription of analgesia in their accident and emergency department.1 Unfortunately, they have failed to answer the question adequately. By failing to reject the null hypothesis (that ethnicity has no effect on prescribing of analgesia in accident and emergency departments) they allow the possibility of a type II error. They did not perform a power calculation, and hence their conclusion that ethnicity is not a risk factor lacks validity.

    To detect a difference of 10% (say 80% v 70%) in prescribing rates between two groups, with a ratio of 5:1 recruitment to the study, the significance level set at 5%, and power of 90%, they would need 255 patients in the Bangladeshi group to show such a …

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