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
