15.16 Consider a problem with three subgroups with the ranks in each subgroup shown as follows. Complete the Kruskal-Wallis test and test the null hypothesis to determine whether the subgroups have equal mean at 10% significance level.

Sample 1 rankings: 7, 2.5, 9.5, 6, 4, 12, 19 Sample 2 rankings: 1, 8, 18, 9.5, 15, 5, 13, 20 Sample 3 rankings: 16, 14, 2.5, 17, 11