is the number of elements in tie g.
A Monte Carlo value based on the given number of random permutations (default 9999) is also given
– the purpose of this is mainly as a control on the asymptotic value.
<=30 (e.g. 15 values in each group), an exact p value is given, based on all possible group
assignments. If available, always use this exact value. For larger samples, the asymptotic
approximation is quite accurate.
Mood’s median test for equal medians
The median test is an alternative to the Mann-Whitney test for equal medians. The median test has
low power, and the Mann-Whitney test is therefore usually preferable. However, there may be cases
with strong outliers where the Mood͛s test may perform better.
The test simply counts the number of values in each sample that are above or below the pooled
median, producing a 2x2 contingency table that is tested with a standard chi-squared test with two
degrees of freedom, without Yate͛s correction.
Kolmogorov-Smirnov test for equal distributions
The Kolmogorov-Smirnov test is a nonparametric test for overall equal distribution of two univariate
samples. In other words, it does not test specifically for equality of mean, variance or any other
parameter. The null hypothesis is H
: The two samples are taken from populations with equal