The following table shows the pesticide residue levels (ppb) in blood samples from four populations of human subjects. Use the Kruskal–Wallis test to test at the .05 level of significance the null hypothesis that there is no difference among the populations with respect to average level of pesticide residue.

Population Population A B C D A B CD 10 4 15 7 44 11 9 4 37 35 5 11 12 7 11 5 12 32 10 10 15 32 9 2 31 19 12 8 42 17 14 6 11 33 6 2 23 8 15 3 9 18 6 5