EXPRESSING AND INTERPRETING THE RESULTS OF QUANTITATIVE RISK ANALYSES- REVIEW AND DISCUSSION

One of the most fundamental problems when using quantitative risk anal yses is related to the way the results of the analyses are expressed a nd interpreted. Should we restrict our attention to unobservable quant ities such as hazard rates and statistically expected values (frequenc ies), or should we focus on the prediction of observable quantities su ch as the occurrence of an accidental, event, the time to a specific e vent occurs, etc.? In this article we review the alternative approache s and discuss the implications concerning e.g. the meaning of 'uncerta inty' of the risk numbers generated. We conclude that in practice ther e is no alternative but adopting the latter approach, focusing on obse rvable quantities and using 'subjective probabilities'. The subjectivi stic (Bayesian) theory of probability provides the framework for the c oherent use of judgement, which constitutes a significant (sometimes t he only) part of the information that is available to us. However, it is not clear to most risk analysts what the Bayesian approach really m eans. There is a strong need for a more attractive presentation of the Bayesian approach. This article intends to contribute to such a prese ntation. (C) 1998 Elsevier Science Limited.