title: A note on the use of the non-parametric Wilcoxon-Mann-Whitney test in the analysis of medical studies.
abstract: BACKGROUND
  Although non-normal data are widespread in biomedical research, parametric tests unnecessarily predominate in statistical analyses.
  
  
  METHODS
  We surveyed five biomedical journals and - for all studies which contain at least the unpaired t-test or the non-parametric Wilcoxon-Mann-Whitney test - investigated the relationship between the choice of a statistical test and other variables such as type of journal, sample size, randomization, sponsoring etc.
  
  
  RESULTS
  The non-parametric Wilcoxon-Mann-Whitney was used in 30% of the studies. In a multivariable logistic regression the type of journal, the test object, the scale of measurement and the statistical software were significant. The non-parametric test was more common in case of non-continuous data, in high-impact journals, in studies in humans, and when the statistical software is specified, in particular when SPSS was used.
authors.affiliation: Institute for Medical Informatics, Biometry and Epidemiology, University of Duisburg-Essen, Essen, Germany. imibe@uk-essen.de
authors.forename: Corinna
authors.initials: C
authors.lastname: Kühnast
authors.forename: Markus
authors.initials: M
authors.lastname: Neuhäuser
references.citation: Stat Methods Med Res. 2003 Jan;12(1):73-84
references.pmid: 12617509
references.citation: Scand J Caring Sci. 2004 Dec;18(4):437-40
references.pmid: 15598252
references.citation: Fundam Clin Pharmacol. 2006 Dec;20(6):515-23
references.pmid: 17109645