Rules

Magnum Opus finds two forms of association: rules and itemsets.  

A rule has two parts, a Left Hand Side (LHS) and a Right Hand Side (RHS). The LHS is a set of one or more attribute values or items. The RHS is a single attribute value or item. Each rule indicates the relationship in the data between examples that have the LHS attribute values or items and those that have the RHS attribute values or items.

A number of values are listed with each rule:

Coverage	The proportion of examples covered by the LHS.
RHS Coverage	The proportion of examples covered by the RHS. (By default this value is not displayed.)
Support	The proportion of examples jointly covered by the LHS and RHS.
Strength	The proportion of examples covered by the LHS that are also covered by the RHS.  Note, when m-estimates are used, a strength estimate is displayed in place of the strength of the rule on the data.
Lift	The strength divided by the proportion of all examples that are covered by the RHS.  Note, when m-estimates are used, a lift estimate is displayed in place of the lift of the rule on the data.
Leverage	The proportion of additional examples covered by both the LHS and RHS above those expected if the LHS and RHS were independent of each other.
Significance	The largest p value for tests for improvement relative to each generalization of the rule. A small p value indicates that the rule probably represents a real improvement upon all of its generalizations.

Magnum Opus supports two rule formats.  The detailed format incorporates a brief description of each value and is recommended for first-time users.   The concise format provides a more concise description of each rule and is intended for experienced users.

A Magnum Opus rule with leverage greater than 0.0 or lift greater than 1.0 identifies a combination of attribute values or items that occur together with greater frequency than might be expected if the values or items were independent of one-another.