rank sum test

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rank sum test

a nonparametric statistical test for ordinal data, testing the null hypothesis that two samples are drawn from the same population against the alternative hypothesis that the two samples are drawn from two populations having probability distributions of the same shape but different locations. It is based on the value of the rank sum statistic, which is calculated as the sum of the ranks of each sample after the observations in both samples are jointly ranked in ascending order; if and only if the null hypothesis is true, the average ranks of the two samples will be similar. Also called Mann-Whitney test, Mann-Whitney U test.

Mann-Whitney test

A statistical test of the probability that two independent sets of observations come from the same population. The Mann-Whitney test is independent of distribution and can be used when the t test is inappropriate.


the place in a series occupied by a value when the series has been set in order according to a particular trait, usually size. Called also order statistic.

rank sum test
nonparametrical statistical test used to compare two methods by seeing if one method contributes more to the higher ranked values.
References in periodicals archive ?
Ao aplicar Mann-Whitney Rank Sum Test observou-se que nao ha diferenca estatisticamente significativa entre as idades, pois os grupos sao iguais entre si, tabela 2.
000572 60 442-526 84 M54894 60 336-414 78 M11167 Table 2 Results of ANOVA and non-parametric Friedman rank sum test for gene expression.
harrisii individuals whose CWs were not significantly different, ranging from 10-13 mm (Wilcoxon's rank sum test, P < 0.
Due to the small sample size and apparent non-normality of many of the response variables, all biological measures were tested using the one-sample exact Wilcoxon rank sum test under the null hypothesis that no change occurred over the time period.
A one-tailed Mann-Whitney Rank Sum test was performed at a 5% level of significance.
The Wilcoxon rank sum test [13] gives us a measure for the statistical significance of the differences between the groups of incipits.
Therefore the next step is to use the Wilcoxon Rank Sum Test of differences of medians.
Pre- and post-lesion turn amplitudes from each animal were compared using the Mann-Whitney rank sum test (SigmaStat, Jandel Scientific).
05 [8]) and then for equal variances before testing either parametrically, by an unpaired t-test, or nonparametrically, by the Mann-Whitney rank sum test.
Using as scores the ranks themselves, leads to a widely known non-parametric statistical procedure, the Wilcoxon (1945) rank sum test.
We examined temporal variation at each site by conducting either a Wilcoxon [TABULAR DATA FOR TABLE 3 OMITTED] rank sum test (for populations with two years of data) or a Kruskal-Wallis test (for populations with three years of data).
We used the two-sided Wilcoxon rank sum test to test the hypothesis that the event R values predicted according to equation [11] are not different from the event R values computed according to Wischmeier and Smith[26], for all erosive events from September through December 1986.