Confidence and risk

The concepts of confidence and risk are discussed with regard to the epistemological (philosophical) basis of risk assessment, and the uncertainty associated with the estimation and quantification of risks. Noting divergent views of the nature of knowledge and science, it is concluded that epistemological issues cannot be objectively resolved or quarantined to protect the ‘objectivity’ of a risk assessment process, and risk communicators should take account of epistemological issues that affect the way communicated results are interpreted and also affect public trust and confidence. In relation to the treatment of uncertain probabilities of failure, a new measure of ‘probabilistic confidence’ is proposed to account for the concern that something may be unsafe (in relation to a target level of safety) and may subsequently fail. This measure of ‘probabilistic confidence’ provides a rational basis for the determination of an appropriate characteristic value for an uncertain probability of failure.