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What is a randomised controlled trial?
  1. Andrea Nelson
  1. Correspondence to Andrea Nelson
    School of Healthcare, University of Leeds, Woodhouse Lane, Baines Wing, Leeds LS2 9UT, UK; e.a.nelson{at}

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Randomised controlled trials (RCTs) answer questions about the effectiveness of different care options: ‘what effect does using treatment A or treatment B have on outcomes?’ RCTs are important to nursing as they are the best study design for answering the question ‘should I do this or that?’; nurses ask effectiveness questions frequently. Researchers refer to one treatment being tested as the ‘intervention’ (I) and another treatment (eg, one that would otherwise be used) as the ‘comparator’ (or control) (C). Examples of these effectiveness questions (as well as their interventions and comparators) include:

  1. ‘Should families of children with eczema install a home water softener?’ (I, water softener; C, …

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  • Competing interests None.