For comparing two small sets of observations, a direct method is quick, and gives insight into the meaning of the "U" statistic, which corresponds to the number of wins out of all pairwise contests (see the tortoise and hare example under Examples below). For each observation in one set, count the number of times this first value wins over any observations in the other set (the other value loses if this first is larger). Count 0.5 for any ties. The sum of wins and ties is "U" (i.e.: formula_7) for the first set. "U" for the other set is the converse (i.e.: formula_8).