Association Rules

The Apriori algorithm calculates rules that express probabilistic relationships between items in frequent itemsets For example, a rule derived from frequent itemsets containing A, B, and C might state that if A and B are included in a transaction, then C is likely to also be included.

An association rule is of the form IF antecedent THEN consequent. An association rule states that an item or group of items, the antecendent, implies the presence of another item, the consequent, with some probability. Unlike decision tree rules, which predict a target, association rules simply express correlation.

Association rules have confidence and support: