Sutton's law states that in attempting to diagnose a problem, one should first do the experiment that can confirm the most likely diagnosis. It is taught in medical schools to guide new doctors in ordering tests in a way that leads to faster treatment, while minimizing unnecessary costs. It is applicable to any process of diagnosis, in many disciplines, such as debugging computer programs. Computer-aided diagnosis provides a statistical and quantitative approach to these kinds of problems.
A more thorough analysis will consider the false positive rate of the test and the possibility that a less likely diagnosis might have more serious consequences.
The law is named after the bank robber Willie Sutton, who reputedly replied to a reporter's inquiry as to why he robbed banks by saying "because that's where the money is." He denied ever saying that in a 1976 book he co-authored, Where the Money Was.
A similar idea is contained in the physician's adage, "When you hear hoofbeats in Texas, think horses, not zebras."