1General principle
Rating a risk means assigning it a position on a matrix that generally combines severity level (the scale of consequences if the scenario occurs) with likelihood oroccurrence (the probability of occurrence). The resulting risk level guides prioritisation: address scenarios that are both severe and likely first.
Rating is always performed in two stages: before measures (inherent risk without protection), followed by after measures (residual risk after existing barriers are considered). The difference between the two measures the actual effectiveness of controls.
Page to be completed — matrix construction, ordinal versus quantified scales, collective-rating pitfalls and links with method-specific metrics for FMEA, PHA and LOPA.