Compute the KruskalWallis Htest for independent samples
The KruskalWallis Htest tests the null hypothesis that the population median of all of the groups are equal. It is a nonparametric version of ANOVA. The test works on 2 or more independent samples, which may have different sizes. Note that rejecting the null hypothesis does not indicate which of the groups differs. Posthoc comparisons between groups are required to determine which groups are different.
Parameters :  sample1, sample2, ... : array_like


Returns :  Hstatistic : float
pvalue : float

Notes
Due to the assumption that H has a chi square distribution, the number of samples in each group must not be too small. A typical rule is that each sample must have at least 5 measurements.
References
[R142]  http://en.wikipedia.org/wiki/KruskalWallis_oneway_analysis_of_variance 