Association Rules are measurements on groups of observations or transactions that contain items of some kind. These measurements seek to describe the relationships between the items in the groups, such as the frequency of occurrence of items together in a group or the probability that items occur in a group given that other specific items are in that group. The nature of items and groups in association analysis and the meaning of the relationships between items in a group will depend on the nature of the data being studied. For example, the items may be products purchased and the groups the market baskets in which they were purchased. (This is generally called market basket analysis). Another example is that items may be accounts opened and the groups the customers that opened the accounts. This type of association analysis is useful in a cross-sell application to determine what products and services to sell with other products and services. Obviously the possibilities are endless when it comes to the assignment of meaning to items and groups in business and scientific transactions or observations.