5. Rank-Sum Test: Apple Trees Commercial apple trees usually consist of two parts grafted together. The upper part, or graft, determines the character of the fruit, while the root stock determines the size of the tree. (Reference: East Malling Research Station, England.) The following data are from two root stocks A and B. The data represent total extension growth (in meters) of the grafts after 4 years.

Stock A 2.81 2.26 1.94 2.37 3.11 2.58 2.74 2.10 3.41 2.94 2.88 Stock B 2.52 3.02 2.86 2.91 2.78 2.71 1.96 2.44 2.13 1.58 2.77 Use a 1% level of significance and the rank-sum test to test the claim that the distributions of growths are different for root stocks A and B. Interpret the results.