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BAYES, THOMAS

An English country clergyman, amateur mathematician, and inveterate gambler, Thomas Bayes (1702–1761) is remembered for his development of ideas and concepts in the theory of probability. These are described in his Essay Towards Solving a Problem in the Doctrine of Chances, published posthumously in 1763. Bayes was interested in the chances of drawing a winning hand in card games, throwing the right combination of numbers with a pair of dice, and picking the winner in a horse race. He expounded on the chance of events occurring on the basis of preexisting circumstances and after the occurrence of particular events, which he termed "prior odds" (or probability) and "posterior odds." His Essay was rediscovered in the twentieth century and was put to service in Bayesian statistics, a branch of stochastic mathematics that does not use statistical significance tests. It has proved very useful in decision analysis, clinical epidemiology, health-services research, and other applications of probability theory.

JOHN M. LAST

(SEE ALSO Bayes' Theorem; Probability Model; Statistics for Public Health)