Endgames Statistical Question

Independent samples t test

BMJ 2010; 340 doi: http://dx.doi.org/10.1136/bmj.c2673 (Published 02 June 2010) Cite this as: BMJ 2010;340:c2673
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, London
  1. p.sedgwick{at}sgul.ac.uk

A new programme of goal oriented visits from a rheumatologist was devised for patients in primary care with osteoarthritis of the knee.1 The new programme was assessed using a randomised controlled trial to ascertain whether it provided benefits in terms of weight management and physical activity. The control treatment was usual care. A total of 154 patients were randomised to the new programme (three goal oriented standardised consultations) and 182 to usual care.

At four months, the mean weight loss for patients who received standardised consultations was on average greater than for those receiving usual care (mean 1.11 (SD 2.49) kg v 0.37 (SD 2.39) kg; P=0.007). The two groups were statistically compared using a two sided, independent samples t test with a 0.05 (5%) critical level of significance (t=2.77, degrees of freedom=334).

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

  • a) Alternative hypothesis: in the total population of patients with knee osteoarthritis, standardised consultations will result in greater weight loss than will usual …

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