Part 2: Wilcoxon Rank-Sum Test Let us consider another hypothetical situation. The WHO wants to compare the mortality rates of children under the age of five years of underdeveloped and developed regions of the world. There were two independent samples of ten countries from each of the groups drawn at the same time, and the yearly mortality rates of children under the age of five years (per 100,000) inhabitants were reported. Table 2: Mortality Rates of Children Country Underdeveloped Developed 1 120 11 2 110 9 3 105 13 61 11 45 14 114 11 7 118 10 138 85 10 70