Birthday of Francis Galton (1822) — Regression to the Mean

Francis Galton was born in Birmingham on February 16, 1822 — a half-cousin of Charles Darwin. Trying to understand heredity, he measured thousands of parents and children and made a discovery that troubled him: the children of very tall parents are, on average, shorter than their parents. The children of very short parents are, on average, taller. This 'regression to the mean' is a mathematical phenomenon, not a biological one — it appears whenever a variable is measured imperfectly and extreme values are partly due to chance. Galton invented correlation, the correlation coefficient r, and regression analysis. These are now the most widely used statistical tools in all of science.