Power dressing and meta-analysis: incorporating power analysis into meta-analysis

J Adv Nurs. 2002 May;38(3):274-80. doi: 10.1046/j.1365-2648.2002.02177.x.


Aims: This paper highlights the lack of consideration that is given to power in the health and social sciences, which is a continuing problem with both single study research and more importantly for meta-analysis.

Background: The power of a study is the probability that it will lead to a statistically significant result. By ignoring power the single study researcher makes it difficult to get negative results published and therefore affects meta-analysis through publication bias. Researchers using meta-analysis, who also ignore power, then compound the problem by including studies with low power that are more likely to show significant effects.

Method: A simple means of calculating an easily understood measure of effect size from a contingency table is demonstrated in this paper. A computer programme for determining the power of a study is recommended and a method of reflecting the adequacy of the power of the studies in a meta-analysis is suggested. An example of this calculation from a meta-analytic study on intravenous magnesium, which produced inaccurate results, is provided.

Conclusion: It is demonstrated that incorporating power analysis into this meta-analysis would have prevented misleading conclusions being reached. Some suggestions are made for changes in the protocol of meta-analytic studies, which highlight the importance of power analysis.

Publication types

  • Review

MeSH terms

  • Bias
  • Data Interpretation, Statistical*
  • Effect Modifier, Epidemiologic
  • Evidence-Based Medicine
  • Humans
  • Infusions, Intravenous
  • Magnesium / therapeutic use
  • Meta-Analysis as Topic*
  • Myocardial Infarction / drug therapy
  • Myocardial Infarction / mortality
  • Reproducibility of Results
  • Research Design / standards*
  • Sample Size
  • Treatment Outcome


  • Magnesium