21. The apparatus as defined in claim 17 , wherein the classification is at least one of a positive classification, a negative classification, a mixed classification or a no opinion classification.
17. An apparatus to analyze a set of electronic messages, the apparatus comprising: a statistics generator to generate a set of probabilities that the set of messages belong to a first classification; a tangible memory; and an index generator to sort the set of messages based on a set of probabilities, assign a first subset of first consecutive ones of the sorted set of messages to a first bucket, assign a second subset of second consecutive ones of the sorted set of messages to a second bucket, a first message of the second bucket being consecutive to a last message of the first bucket with reference to the set of probabilities, determine a mean of probabilities of the first subset of messages assigned to the first bucket, store the mean in the tangible memory, and store, for each one of the messages assigned to the first bucket, an indication that the respective message is assigned to the first bucket in the tangible memory, the index generator is further to move a boundary between the first bucket and the second bucket, recalculate the mean of probabilities of messages assigned to the first bucket in response to moving the boundary, repeatedly (1) move the boundary and (2) recalculate the mean until deviations of the probabilities within the first bucket with respect to the mean are equal to or less than a threshold, and store a last recalculated mean as a representative of the first bucket.