Endgames Statistical Question

What is sampling error?

BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e4285 (Published 27 June 2012) Cite this as: BMJ 2012;344:e4285
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers evaluated the effectiveness of a newly developed behavioural intervention designed to prevent weight gain and improve health related behaviours in women with young children. A cluster randomised controlled trial was used. The intervention group received four interactive group sessions that involved simple health messages, strategies to change behaviour, and group discussion, in addition to monthly support using mobile telephone text messages for 12 months. The control group received one non-interactive information session based on population guidelines on diet and physical activity.1

In total, 250 women aged 25-51 years with a child attending one of 12 primary schools were recruited and randomised as school clusters to the intervention group (n=127) or control group (n=123). The main outcome was weight change from baseline at 12 months. After one year, women in the intervention group had lost on average 0.20 kg (standard deviation 3.66 kg, standard error 0.35 kg), compared to an average weight gain of 0.83 kg (3.69 kg, 0.36 kg) for women in the control group. The researchers reported …

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