The “beer and diapers” rule has acquired legendary status among data miners…
— From The Master Algorithm – How the Quest for the ultimate learning machine will remake our world by Pedro Domingos P. 70
Sets of rules are popular with retailers who are deciding which goods to stock. Walmart was a pioneer in this area. One of their early findings was that if you buy diapers you are also likely to buy beer. Huh?
One interpretation of this is that Mom sends Dad to the supermarket to buy diapers, and as emotional compensation, Dad buys a case of beer to go with them. Knowing this, the supermarket can now sell more beer by putting it next to the diapers, which would have never occurred to it without rule mining.”