Domain experts were asked to give judgments about the fuzzy probabilities regarding all the nodes. They use linguistic terms to describe the fuzzy probabilities and then refine them with membership functions. The assignment of linguistic terms with associated fuzzy membership functions is case-dependent and expert-dependent (a detailed description of the linguistic variables can be seen in Appendix 2 and demonstrated in Table 8). For example, linguistic term “Quite unlikely to happen” was assigned to node “Human Errors” and then defined by fuzzy membership function (0.39,0.40,0.41). Without loss of generality, in this case study triangle (a, b, c) is used although other forms of fuzzy membership function could be employed.