On the Importance of Random Error in the Study of Probability Judgment. Part I: New Theoretical Developments

Erev, Wallsten, and Budescu (1994) demonstrated that over- and underconfidence can be observed simultaneously in judgment studies, as a function of the method used to analyze the data. They proposed a general model to account for this apparent paradox, which assumes that overt responses represent true judgments perturbed by random error. To illustrate that the model reproduces the pattern of results, they assumed perfectly calibrated true opinions and a particular form (log-odds plus normally distributed error) of the model to simulate data from the full-range paradigm. In this paper we generalize these results by showing that they can be obtained with other instantiations of the same general model (using the binomial error distribution), and that they apply to the half-range paradigm as well. These results illustrate the robustness and generality of the model. They emphasize the need for new methodological approaches to determine whether observed patterns of over- or underconfidence represent real eAects or are primarily statistical artifacts. #1997 by John Wiley & Sons, Ltd.

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