A method and apparatus for finding the best or near best binary classification of a set of observed events, according to a predictor feature X so as to minimize the uncertainty in the value of a category feature Y. Each feature has three or more possible values. First, the predictor feature value and the category feature value of each event is measured. From the measured predictor feature values, the joint probabilities of each category feature value and each predictor feature value are estimated. The events are then split, arbitrarily, into two sets of predictor feature values. From the estimated joint probabilities, the conditional probability of an event falling into one set of predictor feature values is calculated for each category feature value. A number of pairs of sets of category feature values are then defined where each set SYj contains only those category feature values having the j lowest values of the conditional probability. From among these pairs of sets, an optimum pair is found having the lowest uncertainty in the value of the predictor feature. From the optimum sets of category feature values, the conditional probability that an event falls within one set of category feature values; is calculated for each predictor feature value. A number of pairs of sets of predictor feature values are defined where each set SXi(t + 1) contains only those predictor feature values having the i lowest values of the conditional probability. From among the sets SXi a pair of sets is found having the lowest uncertainty in the value of the category feature. An event is then classified according to whether its predictor feature value is a member of the set of optimal predictor feature values.