14.3 SUPPORT, CONFIDENCE, AND LIFT
Measures of goodness of an association rule include support, confidence, and lift. The support for a particular association rule A ⇒ B is the proportion of transactions in D that contain both A and B. That is,
![equation](https://static.packt-cdn.com/products/9781119526810/graphics/images/c14-disp-0002.png)
The confidence of the association rule A ⇒ B is a measure of the accuracy of the rule, as determined by the percentage of transactions in D containing A that also contain B. In other words,
![equation](https://static.packt-cdn.com/products/9781119526810/graphics/images/c14-disp-0003.png)
In the language of probability, confidence represents the conditional probability of B, given A.
For example, consider the association rule, “If buy squash, then buy beans,” where A represents squash and B represents beans...