Study design

doi:10.1136/bmj.b2381

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Philip Sedgwick, senior lecturer in medical statistics

¹Centre for Medical and Healthcare Education, St George’s, University of London, London SW17 0RE

p.sedgwick{at}sgul.ac.uk

A clinical trial investigated the effectiveness of topical versus oral ibuprofen for chronic knee pain in people over 50. In designing a trial to decide the best treatment approach, which answer best describes how confounding could be minimised?