We study the problem of obtaining an expected utility representation for a potentially incomplete preference relation over lotteries by means of a set of von Neumann-Morgenstern utility functions. It is shown that, when the prize space is a compact metric space, a preference relation admits such a multi-utility representation provided that it satisfies the standard axioms of expected utility theory. Moreover, the representing set of utilities is unique in a welldefined sense. r

We conduct two experiements of the claim that people are overcon…dent. We develop new tests of overplacement which are based on a formal Bayesian model. Our two experiments, on easy quizzes, …nd overplacement. More precisely, we …nd apparently overcon…dent data that cannot be accounted for by a rational population of expected utility maximizers with a good understanding of the nature of the quizzes they took.

We introduce a procedural model of risky choice in which an individual is endowed with a core preference relation that may be highly incomplete. She can, however, derive further rankings of alternatives from her core preferences by means of a procedure based on the independence axiom. We find that the preferences that are generated from an initial set of rankings according to this procedure can be represented by means of a set of von Neumann-Morgenstern utility functions, thereby allowing for incompleteness of preference relations. The proposed theory also yields new characterizations of the stochastic dominance orderings.

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We conduct two experiements of the claim that people are overcon…dent. We develop new tests of overplacement which are based on a formal Bayesian model. Our two experiments, on easy quizzes, …nd overplacement. More precisely, we …nd apparently overcon…dent data that cannot be accounted for by a rational population of expected utility maximizers with a good understanding of the nature of the quizzes they took.