Association Analysis Output Terms 

To configure association analysis in SAP BW and understand its output, one must first understand certain data mining terms:

    *  Support — This is a percentage of how often a collection of tem in an association appears. For example, five percent of the total purchases at an airport sundry shop support the sale of both toothbrush and toothpaste.

    *  Confidence — From a statistical perspective, confidence has a close association with conditional probability. It is the percentage likelihood that a dependent item occurs in a data set when a lead item has occurred. For the diapers (lead item) and beer (dependent item) association, confidence could be expressed as a 50 percent probability of beer being purchased given a sale of diapers. This number is observational rather than predictive.

    *  Lift — This is a measure of the effectiveness of an association analysis by taking the ratio of the results with and without the association rule. Lift can be used to eliminate records that do not have a true association but are picked up in the analysis because they appear frequently. More explicitly, lift is confidence divided by support for a given association. The actual mathematical formula the system applies is as follows: Lift is equal to the actual support of the lead and dependent items divided by the ratio of actual support for lead item to actual support of dependent item. Fractions are used in the equation rather than percentages.