Magnum Opus finds two forms of association: rules and itemsets. A Magnum Opus itemset is a set of attribute values or items. The search options enable the user to control the types of itemset that are found. By default, Magnum Opus finds itemsets that maximize leverage.
A number of measures are listed with each itemset:
| Coverage | The proportion of examples covered by the itemset. |
| Leverage | The proportion of examples covered by the itemset in excess of the maximum that can be explained by assuming independence between any subsets of the itemset. |
| Significance | The largest p value for tests for improvement relative to each partition of the itemset. A small p value indicates that the itemset probably represents a real improvement upon all of its subsets. |
Magnum Opus supports two itemset formats. The detailed format
incorporates a brief description of each measure and is recommended for first-time users.
The concise format provides a more concise description of each itemset and is intended
for experienced users.