The confidence of an [[Association Rules|association rule]] $A \rightarrow C$ is a [[Error Metrics|metric]] measuring the [[Probability|probability]] of seeing the consequent in a transaction where the antecedent appears. It lies in the range $[0,1]$ and can be defined using the [[Support of an Item Set|support]] as: $ \text{confidence}(A \rightarrow C) = \frac{ \text{support}(A \rightarrow C) }{ \text{support}(A) } $