the probability that a certain event will occur given that other related events have been observed. For example, assume that Basket A contains 10 white cards and 20 red cards, while Basket B contains 20 white cards and 10 red cards. If one selects a card from a basket at random, without noting the color, the probability that it will be from Basket A is .5, since the only possibilities are A or B. If, however, the color of the card is noted, then one must take this additional information into account in determining the probability that the card came from Basket A. For example, the probability that a white card will be pulled from Basket A would be revised downward from .5 according to Bayes theorem: Since there are fewer white cards in A, a white card is more likely to be drawn from B instead. See also prior probability.