Northwest Airlines wants to determine if the number of no-shows for flights originating from Detroit is higher than in Minneapolis. A sample of twenty flights from each city is taken and the number of no-shows is determined for each flight. Which nonparametric test would you use to determine whether the number of no-shows is greater in Detroit?
A. Wald-Wolfowitz test.
B. Wilcoxon signed rank test.
C. Mann-Whitney test.
D. Kruskal-Wallis test.