1) You measure the height of 11 oak trees and 9 maple trees. Is there a difference in height? Use a MannWhitney U test (do NOT use R):

Oak trees: 55 74 60 29 37 106 63 57 50 68 110

Maple trees: 70 98 96 68 86 108 86 86 100

Note: this should be two sided - why??