Upon observing a signal, a Bayesian decision maker updates her probability distribution over the state space, chooses an action, and receives a payoff that depends on the state and the action taken. An information structure determines the set of possible signals and the probability of each...

In Ellsberg paradox, decision makers that are partially informed about the actual probability distribution violate the expected utility paradigm. This paper develops a theory of decision making with a partially specified probability. The paper takes an axiomatic approach using Anscombe-Aumann's...