The KruskalWallis test is a distribution free (nonparametric) alternative to ANOVA. It compares several samples and tests the hypothesis:
H_{0} the samples are all drawn from populations that have equal means
H_{1} the mean of at least one of the populations is different
The test involves:
 sort the combined results into size order and allocate ranks
 form a table that contains the ranks, instead of the values
 calculate the test statistic 'K using the formula:
Where:
R_{i} 
sum of the ranks in row 'i' 
J 
number of values in row 'i' 
I 
number of rows 
N 
total number of values 
'K' has an approximately χ ^{2} distribution with degrees of freedom I  1
