A rule of thumb is a homemade recipe for making a guess. It is an easy-to-remember guide that falls somewhere between a mathematical formula and a shot in the dark. A farmer, for inÂstance, knows to plant his corn when oak leaves are the size of squirrels’ ears. An economics profesÂsor knows from sad experience that inviting more than 25 percent of the guests for a univerÂsity dinner party from the economics departÂment ruins the conversation. Rules of thumb are a kind of tool. They help you appraise a problem or situation. They make it easier to consider the subtleties of the topic at hand; they give you a feel for a subject.
via Boing Boing