Human Cognitive Reliability Correlation - Disadvantages of HCR

Disadvantages of HCR

• The HEP produced by HCR is not complete; it calculates the probability that a system operator will fail to diagnose and process information, make a decision and act within the time available. It does not give any regard to misdiagnoses or rule violations.
• The same probability curves are used to model non-detection and slow response failures. These are very different processes, and it is unlikely that identical curves could model their behaviour. Furthermore, it is uncertain as to whether such curves could be applied to situations in which detection failures or processing difficulties are the primary dominating factors of influence.
• The rules for judging Knowledge-based, Skill-based and Rule-based behaviour are not exhaustive. Assigning the wrong behaviour to a task can mean differences of up to two orders of magnitude in the HEP.
• The method is very sensitive to changes in the estimate of the median time. Therefore, this estimate requires to be very accurate otherwise the estimation in the HEP will suffer as a consequence.
• It is highly resource intensive to collect all the required data for the HCR methodology, particularly due to the necessity of evaluation for all new situations which require an assessment.
• There is no sense of output from the model that indicates in any way of how human reliability could be adjusted to allow for improvement or optimisation to meet required goals of performance.
• Only three PSFs are included in the methodology; there are several other PSF’s that could affect performance which are unaccounted for.
• The model is relatively insensitive to PSF changes as opposed to, for example, time parameter changes.
• As the HCR correlation was originally developed for use within the nuclear industry, it is not possible to use the methodology for applications out-with this domain.