English mathematician for whom Bayes' theorem is named (1702-1761)

(statistics) a theorem describing how the conditional probability of a set of possible causes for a given observed event can be computed from knowledge of the probability of each cause and the conditional probability of the outcome of each cause

(statistics) the difficulty of applying Bayes' theorem is that the probabilities of the different causes are seldom known, in which case it may be postulated that they are all equal (sometimes known as postulating the equidistribution of ignorance)