Suppose we have a randomly sampled (i.i.d.) dataset, a set of pairs (Wi , Di), i = 1, . . . n. Here, Di is a dummy (or "binary" or "indicator") variable such that Di = 1 if female, Di = 0 if male. Wi represents weight of the individual, in kg. The researcher uses this dataset to divide up (Wi , Di) into two subgroups: one where Di = 1 (the female group), and one where Di = 0 (and the male group). Let female and male be the true means of the female and male group weights. The researcher is interested in female male