Endgames Statistical Question

Convenience sampling

BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f6304 (Published 25 October 2013) Cite this as: BMJ 2013;347:f6304
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers assessed the efficacy, acceptability, and safety of a topical alkane vapocoolant spray in reducing pain during intravenous cannulation in adults. A randomised double blind placebo controlled trial study design was used. The intervention was a blend of propane, butane, and pentane, which was sprayed less than 15 seconds before cannulation on to the relevant area of skin from a distance of 12 cm for two seconds. The control treatment was a water spray. The primary outcome measure was pain during cannulation, measured with a 100 mm visual analogue scale. Secondary outcome measures included discomfort during administration of the spray, success rate of cannulation, and side effects of treatment.1

Participants were adults who required intravenous cannulation in the emergency department of a metropolitan teaching hospital. In total, 201 adult patients were recruited using convenience sampling. The intervention group consisted of 109 (54%) men, who had a mean (standard deviation) age of 58.2 (19.5) years. The researchers concluded that topical alkane vapocoolant spray was effective, acceptable, and safe in reducing pain during peripheral intravenous cannulation in adults in the emergency department.

Which of the following statements, if …

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