The confidence of an association rule is a percentage
value that shows how frequently the rule head occurs among all the
groups containing the rule body. The confidence value indicates how
reliable this rule is. The higher the value, the more likely the head
items occur in a group if it is known that all body items are contained
in that group.
Thus, the confidence of a rule is the percentage equivalent of
m/
n,
where the values are:
- m
- The number of groups containing the joined rule head and rule
body
- n
- The number of groups containing the rule body
As in the case of the support factor, you can specify that only
rules that achieve a certain minimum level of confidence are included
in your mining model. This ensures a definitive result, and it is,
again, one of the ways in which you can control the number of rules
that are created.
You set minimum confidence as part of defining mining settings.