ABSTRACT
Galton made important contributions to statistics and genetics, but he was also one of the first proponents of eugenics, a scientifically flawed philosophical movement favored by many biologists of Galton’s time but with horrific historical consequences. In this chapter, the authors explain that the line averages follow is what the people call the regression line, which improves the precision of their estimates. However, it is not always appropriate to estimate conditional expectations with the regression line so the people also describe Galton's theoretical justification for using the regression line. Galton used mathematical statistics to demonstrate that, when two variables follow a bivariate normal distribution, computing the regression line is equivalent to computing conditional expectations. Therefore, the people can obtain a much more stable estimate of the conditional expectation by finding the regression line and using it to predict.
