Rules Tables

The rules tables display information for the top rules, with ranks based on the selected evaluation statistic. This example includes information for the top 10 rules ranked by confidence and ranked by rule support. Each table contains the values of all the evaluation statistics for each rule.

Confidence

Confidence is the percentage of correct rule predictions: the percentage of cases for which the predicted value is correct when the conditions of the rule are true.

Figure 1. Rules ranked by confidence
Rules ranked by confidence
  • The top rule, ranked by confidence, has a confidence value of 49.16%. When the conditions in the rule are true, the predicted value is correct almost half of the time.
  • The top six rules have fairly low lift values. Lift is a measure of how much the rule improves prediction compared to random chance. It is the ratio of correct predictions to the overall occurrence of the predicted value.
  • Rules 7 through 10 predict major theft rather than minor theft, and those roles also have higher lift values than the rules that predict minor theft.

Rule support

Rule support is the percentage of cases for which the rule is true. For example, if the rule is "If property value is less than x and population is greater than y, then type of crime is z," rule support is the actual percentage of census tracts for which the property value is less than x, the population is greater than y, and the most common (modal) crime is z.

Figure 2. Rules ranked by rule support
Rules ranked by rule support
  • The top four rules ranked by rule support are also in the top ten rules ranked by confidence. "Rule ID" is also the confidence ranks value.
  • Rules 16, 17, 18, and 19 (rule support ranks 5, 6, 8, and 10) have substantially higher lift values than the other top rules ranked by rule support. For those rules, the accurate prediction rate is approximately twice as good as random assignment.
  • The rules with better lift values also involve prediction of more serious crimes. Rule 16 (rule support rank 5) predicts violent crimes in areas with lower property values. The confidence of the rule is 20.46%, but the lift value of the rule is 2.05.