Endgames Statistical Question

What is intention to treat analysis?

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f3662 (Published 07 June 2013) Cite this as: BMJ 2013;346:f3662
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers investigated the effectiveness of a home based early intervention on children’s body mass index at age 2 years. A randomised controlled trial was used. The intervention consisted of eight home visits from specially trained community nurses in the first 24 months after birth. This intervention was in addition to the usual childhood nursing services from community health service nurses. The control group received the usual childhood nursing services alone. Participants were first time mothers and their infants.1

The primary outcome was the child’s body mass index at age 2. In total, 667 first time mothers and their infants were recruited to the trial; 337 were allocated to intervention and 330 to control. An intention to treat analysis showed that mean body mass index was significantly lower in the intervention group (16.53) than in the control group (16.82) (mean difference −0.29, 95% confidence interval −0.55 to −0.02; P=0.04).

Which of the following statements, if any, describe intention …

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