In the field of Safety Engineering, probabilistic and deterministic mathematical representations are used to calculate how likely an event may occur, which could lead to a major hazard. Although there are several different interpretations, probability theory treats the concept in a rigorous mathematical manner, by expressing it through a set of axioms. Typically these axioms formalise probability in terms of a probability space, which assigns a measure taking values between 0 and 1, termed the probability measure, to a set of outcomes called the sample space. Any specified subset of these outcomes is called an event.