On Probabilities in Bridge
Abstract In the game of bridge, the probability of a successful finesse, or a favorable “break” in a suit, depends not only upon the original deal, but also upon all the bids and plays which have been made by one's opponents. The widely quoted a priori probabilities, based solely upon the deal, are not generally correct, and are often misleading, after play has begun. This paper shows that the evaluation of probabilities during the course of play of bridge requires the use of the Bayes formula. Two examples are given to illustrate the proper application of that formula to the measurement of probabilities in typical situations arising in bridge.