The base rate fallacy in belief reasoning

The base rate fallacy is an error that occurs when the conditional probability of some hypothesis y given some evidence x is assessed without taking account of the ”base rate” of y, often as a result of wrongly assuming equality between the inverse conditionals, expressed as: p(y|x) = p(x|y). Because base rates and conditionals are not normally considered in traditional Dempster-Shafer belief reasoning there is a risk of falling victim to the base rate fallacy in practical applications. This paper describes the concept of the base rate fallacy, how it can emerge in belief reasoning and possible approaches for how it can be avoided.