Psychology
787 strangers guessed an ox's weight. The crowd average missed it by 1 pound.
At a 1906 country fair, statistician Francis Galton collected 787 guesses of an ox's dressed weight from a crowd of butchers, farmers and passersby. No individual guess came close, but the average of all 787 guesses was 1,197 lbs against a true weight of 1,198 lbs. Galton, a skeptic of ordinary judgment, published the result anyway: a crowd's aggregated guess can beat almost every expert in it.