Incomplete probability assessments in decision analysis

In analysing a decision problem, in a situation of partial knowledge, a decision maker may be reluctant to assign a complete probability distribution on the relevant states of nature. In order to face this difficulty, several methods, based on indeterminate probabilities or probability intervals, have been proposed in the literature. In this paper, arguing that it is meaningless to judge probabilistic assessments as correct or wrong, it is maintained that only coherence has an objective and significant role. Then to overcome practical difficulties, an approach based on the subjective methodology and on the use of numerical and qualitative probabilities, is outlined.