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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. E-mail:
umokeh1@yahoo.com. Tel: +2348034304278.
Accepted
11 December, 2009 |
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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. |
