Endgames Statistical Question

Reference and normal ranges

BMJ 2010; 341 doi: https://doi.org/10.1136/bmj.c6666 (Published 24 November 2010) Cite this as: BMJ 2010;341:c6666
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Section of Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers recorded the forehead temperature of 1000 apparently healthy subjects aged between 18 and 65 years using a handheld infrared thermometer.1 The sample mean forehead temperature was 33.3°C, with a standard deviation of 1.18°C. The normal range for forehead temperature, calculated as 1.96 standard deviations either side of the sample mean, was reported as 31.0-35.6°C.

A separate study measured a series of immunohaematological variables in 150 healthy adults to establish haematological reference ranges for HIV negative adults from the Central African Republic.2 Ranges for each variable were derived as the interval from the 2.5th to 97.5th centile of the sample measurements. The reference range for erythrocyte counts was reported to be 4.50-6.10×1012/l for men and 3.42-5.44×1012/l for women.

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

  • a) People with a forehead temperature outside the …

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