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The evaluation of risks provides a judgment concerning the acceptability or the need of mitigations, according to the comparison between the risk profile and the risk appetite. The stage is a decision-making process in which, if the risk is acceptable, the assessment can be terminated, otherwise it goes on to next stage of treatment and management. To verify the acceptability after the interventions, the results of the mitigations have to be iteratively compared to the expected targets. At this stage it is possible to use, with adaptation when necessary, methods and techniques widely tested in safety management:
- Event Tree Analysis (ETA) and Fault Tree Analysis (FTA): analysis of the cause-effect tree of the risk profile. The top event (an event that is at the end of the shaft) is usually a cause of loss of value in the organization, related to exclusionary or concurrent events of a lower-level type;
- Failure Modes Effects Analysis (FMEA) and Failure Modes Effects and Criticality Analysis (FMECA): FMEA is a technique that allows a qualitative analysis of a system, decomposing the problem in a hierarchy of functions up to a determined level of detail. For each of the constituents, possible "failure modes" (adverse events) are identified and actions to eliminate or reduce the effects can be considered. FMECA adds a quantitative assessment of the criticalities: for each mode, an index is calculated as the combination of the occurrence of the event, the severity of its effects and the detectability of the symptoms;
- Hazard and Operability (HAZOP) analysis: qualitative methodology that has both deductive (search for causes) and inductive (consequence analysis) aspects. The method seeks for the risks and operational problems that degrade system performances and then find solutions to the problems identified;
- Multi-criteria decision tools (i.e. Analytic Hierarchy Process and Analytic Network Process): decision support techniques for solving complex problems in which both qualitative and quantitative aspects have to be considered. Through a hierarchical or network modeling, the definition of a ranking of the critical aspects of the problem is enabled. Multi-criteria decision tools give an effective support mainly where the consequences of an event can be both positive and negative, applying cost-benefit analysis.
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