Supplementing quantitative risk assessments with a stage addressing the risk understanding of the decision maker

A quantitative probabilistic risk assessment produces a conditional risk description given the knowledge of the analysts (formulated to a large extent through assumptions). However, important aspects of the risk may be concealed in the background knowledge of the analyst and the assumptions. This paper discusses this issue, the main purpose being to present a two-stage risk assessment approach where the second stage addresses the risk understanding of the decision maker. This second-stage is to a large extent qualitative. The approach is novel with its separation between the analysts׳ conditional risk descriptions using probability judgments, and the decision maker׳s risk understanding. The approach aims at improving the use of risk assessment in practical decision making by ensuring that the results of the risk assessments are properly interpreted and the key aspects of risk, uncertainty and knowledge are brought to attention for the decision makers. Examples are used to illustrate the approach.