Endgames Statistical Question

Uncertainty in sample estimates: sampling error

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1914 (Published 10 April 2015) Cite this as: BMJ 2015;350:h1914
  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. p.sedgwick{at}sgul.ac.uk

The effects of a shared care obesity management programme on body mass index (BMI) and related outcomes in obese children were investigated using a randomised controlled trial. The intervention consisted of general practice surveillance for childhood obesity, followed by obesity management across primary and tertiary care settings using a shared care model. The intervention was delivered over one year. The control treatment consisted of “usual care.” Participants were children aged 3-10 years who had a BMI above the 95th centile for their age and sex. The setting was Melbourne, Australia. In total, 118 children were recruited through their general practice and randomised to the intervention (n=62) or control (n=56).1

The primary outcome was BMI. Measurements of BMI were transformed to z scores. At the end of follow-up, the intervention group had a smaller mean BMI z score than the control group, although the difference was not significant (2.0 (standard deviation 0.5) v 2.0 (0.4); adjusted mean difference −0.05, 95% confidence interval −0.14 to 0.03; P=0.2). No evidence of a significant difference was found for any secondary outcome, including body fat percentage, waist circumference, physical activity, quality of diet, and health related quality of life. It was concluded that the shared care model of primary and tertiary care management had no effect on BMI and related outcomes in obese children.

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

  • a) The sample estimates …

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