| The Kruskal-Wallis
test is a distribution free (nonparametric)
alternative to ANOVA.
It compares several samples and tests
the
hypothesis:
H0 the samples are all drawn
from populations that have equal means
H1 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:
| Ri |
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
|
