A common and deceptively simple step in research is making group comparisons in terms of some ordered characteristic such as age, income, occupational prestige, and the like. Ideally these comparisons are best made graphically, with the entire frequency distribution presented for each group. However, summary measures are generally used because it is impractical to present a large number of graphs and because quantitative measures allow the results to be correlated with other attributes of the groups. Thus researchers usually turn to such well-known measures of central tendency as arithmetic means and medians or to such dis-The author wishes to thank Leo A. Goodman, Donnell M. Pappenfort, and Otis Dudley Duncan for helpful suggestions and Guy Dalto for his as-sistance in the computations for this chapter. The figures were prepared by John Pershing. This chapter is a by-product of research conducted under a grant from the National Science Foundation and a fellowship from the Guggenheim Foundation.