Biotechnology and Molecular Biology Reviews

  • Abbreviation: Biotechnol. Mol. Biol. Rev.
  • Language: English
  • ISSN: 1538-2273
  • DOI: 10.5897/BMBR
  • Start Year: 2006
  • Published Articles: 102


Statistical analysis of the application of Wilcoxon and Mann-Whitney U test in medical research studies

U. M. Okeh
Department of Industrial Mathematics and Applied Statistics, Ebonyi State University, Abakaliki Nigeria
Email: [email protected]

  •  Accepted: 11 December 2009
  •  Published: 31 December 2009


Although non-normal data are widespread in biomedical research, parametric tests unnecessarily, predominate in statistical analyses. Five biomedical journals were surveyed and for all studies which contain at least the unpaired t-test or the non-parametric Wilcoxon and Mann-Whitney U test - investigated the relationship between the choice of a statistical test and other variables such as type of journal, sample size, randomization, sponsoring etc. The non-parametric Wilcoxon and Mann-Whitney U were 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.


Key words: Wilcoxon and Mann-Whitney U test, univariate analyses, non-parametric test, logistic regression.