Why Every Clinician Should Know Bayes’ Rule

We argue that knowledge about the rationale for Bayes' rule and about its proper application is a crucial tool for every clinician. We explain why such probabilistic reasoning is so important. We then acknowledge that the rule is quite abstract and may be difficult to use, and we offer a guideline to overcome this difficulty. We illustrate our text with an example from the mental health domain, but indicate that the same reasoning applies to every clinical area. Finally, we give a five-step recipe for interpreting test results properly.