title: Power dressing and meta-analysis: incorporating power analysis into meta-analysis.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Applied Psychology, Durham University SC, University Boulevard, Thornaby, Stockton on Tees, UK. j.j.muncer@durham.ac.uk
authors.forename: Steven
authors.initials: S
authors.lastname: Muncer
authors.forename: Shirley
authors.initials: S
authors.lastname: Taylor
authors.forename: Mark
authors.initials: M
authors.lastname: Craigie
mesh_terms: D015982:Bias; D003627:Data Interpretation, Statistical; D015987:Effect Modifier, Epidemiologic; D019317:Evidence-Based Medicine; D006801:Humans; D007262:Infusions, Intravenous; D008274:Magnesium / Q000627:therapeutic use; D015201:Meta-Analysis as Topic; D009203:Myocardial Infarction / Q000188:drug therapy / Q000401:mortality; D015203:Reproducibility of Results; D012107:Research Design / Q000592:standards*; D018401:Sample Size; D016896:Treatment Outcome
chemical_list: D008274:Magnesium