Relation Between Individual and Racial Variability

Abstract

MR. BREWSTER'S memoir refers to “allied races” without defining that phrase, but apparently basing it on the idea of divergent races sprung from a common source. The mean (or typical) characters of these races differing from one another, as individuals of the same race differ among themselves, two systems of variables exist in respect to each and every character: (1) a single system, referring to the means of the different races; (2) several separate systems, referring alike to the individual values of the same character; in each and every race. He supposes the ordinary law of frequency to be approximately applicable to both systems, so that the peculiarities of every series admit of being roughly expressed by its own mean and quartile (= probable error). In order to reduce the variability of each series to a common scale, he works, not with the observed quartiles, but with what may be called reduced quartiles, namely the indices formed by dividing each quartile by its corresponding mean. These being comparable on equal terms, are his “measures of variability.”