Screening, sensitivity, and uncertainty for the CREAM method of human reliability analysis

Tim Bedford, Clare Bayley, Matthew Revie

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


This paper reports a sensitivity analysis of the Cognitive Reliability and Error Analysis Method for Human Reliability Analysis. We consider three different aspects: the difference between the outputs of the Basic and Extended methods, on the same HRA scenario; the variability in outputs through the choices made for common performance conditions (CPCs); the variability in outputs through the assignment of choices for cognitive function failures (CFFs). We discuss the problem of interpreting categories when applying the method, compare its quantitative structure to that of first generation methods and discuss also how dependence is modelled with the approach. We show that the control mode intervals used in the Basic method are too narrow to be consistent with the Extended method. This motivates a new screening method that gives improved accuracy with respect to the Basic method, in the sense that (on average) halves the uncertainty associated with the Basic method. We make some observations on the design of a screening method that are generally applicable in Risk Analysis. Finally we propose a new method of combining CPC weights with nominal probabilities so that the calculated probabilities are always in range (ie between 0 and 1), while satisfying sensible properties that are consistent with the overall CREAM method.
Original languageEnglish
Pages (from-to)100-110
Number of pages11
JournalReliability Engineering and System Safety
Early online date7 Mar 2013
Publication statusPublished - Jul 2013


  • human reliability analysis
  • error analysis
  • risk analysis


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