Aleatory and epistemic uncertainty in probability elicitation with an example from hazardous waste management

The quantification of a risk assessment model often requires the elicitation of expert judgments about quantities that cannot be precisely measured. The aims of the model being quantified provide important guidance as to the types of questions that should be asked of the experts. The uncertainties underlying a quantity may be classified as aleatory or epistemic according to the goals of the risk process. This paper discusses the nature of such a classification and how it affects the probability elicitation process and implementation of the resulting judgments. Examples from various areas of risk assessment are used to show the practical implications of how uncertainties are treated. An extended example from hazardous waste disposal is given.