Abstract
Three explanations have been advanced to explain the most popular error on probabilistic inference word problems, which is the use of the reliability of the evidence p(E/H) as the response when p(H/E) is requested. Production system simulations of each explanation are applied to data from a study in which 265 subjects judged the probability of an hypothesis after receiving each of three pertinent pieces of information—the evidence, the baserate, and the reliability of the evidence—in all possible combinations. The explanation that subjects consider the baserate to be irrelevant is rejected. Data are consistent with both the explanation that 265 subjects confuse p(E/H) with p(H/E) and the explanation that they interpolate between the baserate probability and 1.0 and then select their response from among nearby numbers that are available in the word problem.
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