ABSTRACT
Within the context of performance assurance (i.e. the consideration of factors necessary to ensure system performance within acceptable tolerances), human error is of paramount importance, especially in safety-critical systems. Many analysis methods can be used to investigate the role of human fallibility in systems (e.g. SHERPA, human HAZOP; see Kirwan 1992a). Used as Human Error Identification (HEI) techniques, they are often applied within the framework of Probabilistic Risk Assessment (PRA), where the set of undesirable events that could occur within a system is defined, along with the paths that lead to them and the probability of their occurrence. The assessment and use of Human Error Probabilities (HEPs) has been criticized when applying absolute error probabilities (Hollnagel 1993). The authors
would argue that HEPs are more reliable when comparing relative error probabilities associated with different parts of a task than when used to give absolute error probabilities.
