“Transmuting” Women into Men

The first two regression lines, and the first correlations, were calculated by Francis Galton, in his work on heredity in sweet peas and in humans. When “regressing” the heights of adult children on those of their parents, Galton had to deal with the fact that men are generally taller than women—but without modern-day statistical tools such as multiple regression and partial correlation. This article uses the family data on stature, which we obtained directly from Galton's notebooks, to (a) compare the sharpness of his methods, relative to modern-day ones, for dealing with this complication; and (b) estimate the additional familial component of variance in stature beyond that contributed by the parental heights. In keeping with Galton's plea for “a manuscript library of original data,” these historical and pedagogically valuable data are now available to the statistical community as digital photographs and as a dataset ready for further analyses.