ABSTRACT
This chapter shows that the probability concept is an essential tool for measuring and describing risk, in particular how large or small the risks are. It discusses the probability concept, which gives a basis for introducing and discussing the risk characterizations. The chapter presents common risk metrics, such as expected values and value-at-risk. It also discusses the risk of getting a disease and the risk related to defective units in a production process. Probability models are commonly used in probability theory and statistics. Well-known types of probability models are binominal, Poisson and normal. A common approach is to use probability as the uncertainty description, but it should always be supplemented with judgments of the strength of the knowledge (SoK) supporting the probabilities. It is challenging to compare risk levels when using probability distributions and SoK judgments.
