Rule strength (confidence)

The strength of a rule is the proportion of examples covered by the LHS of the rule that are also covered by the RHS.  It indicates the probability that a case will satisfy the RHS if it satisfies the LHS.

For example, suppose that the LHS covers 200 examples and the RHS covers 50 of the examples covered by the LHS. The strength is 50/200 = 0.25.

Note, when m-estimates are used, a strength estimate is displayed in place of the strength of the rule on the data.

Note that strength is often called confidence.