Lift for AR Rules

Both support (Support for AR Rules) and confidence (Confidence for AR Rules) must be used to determine if a rule is valid. However, there are times when both of these measures may be high, and yet still produce a rule that is not useful.

Lift indicates the strength of a rule over the random co-occurrence of the antecedent and the consequent, given their individual support. It provides information about the improvement, the increase in probability of the consequent given the antecedent. Lift is defined as follows.

(Rule Support) /(Support(Antecedent) * Support(Consequent))

Lift can also be defined as the confidence of the combination of items divided by the support of the consequent.