Summary

Of the investigations described in this book, 4 show that trained experts perform better in their area of expertise than do ordinary respondents, who are usually untrained students. Another 4 investigations show that statistically trained students perform better on tests of probability than do statistically naive students. In addition, 6 investigations show that a relatively brief training in the laboratory can improve untrained people's dealing with probabilities.

Training improves dealing with probabilities

The results reported in this book demonstrate that many untrained people fail to deal with probabilities correctly, and that they can be trained to perform better. The picture is fairly typical of the literature on dealing with probabilities (Edwards, 1983, p. 508; Phillips, 1983 p. 526). However, the results do not abolish the need to investigate the effects of training. In everyday life novel tasks often have to be performed without special training. It is important to find out what heuristics untrained people use, how quickly they learn the normative rules, and how successfully they then apply them.

Experts

Entry 1.1 A in Table 15.1 (Lichtenstein and Fischhoff, 1980a, Table 1; see Chapter 3, Employ trained experts) describes the performance of 8 experts in subjective probability. The experts do not show apparent overconfidence in their answers to 2-choice general knowledge questions, when using a one-sided rating scale with probabilities ranging only from .5 through 1.0.