Measuring variability of procedure progression in proceduralized scenarios

Various performance shaping factors (PSFs) have been presented to explain the contributors to unsafe acts in a human failure event or predict a human error probability of new human performance. However, because most of these parameters of an HRA depend on the subjective knowledge and experience of HRA analyzers, the results of an HRA insufficiently provide unbiased standards to explain human performance variations or compare collected data with other data from different analyzers. To secure the validity of the HRA results, we propose a quantitative measure, which represents the variability of procedure progression (VPP) in proceduralized scenarios. A VPP measure shows how differently the operators follow the steps of the procedures. This paper introduces the sources of the VPP measure and relevance to PSFs. The assessment method of the VPP measure is also proposed, and the application examples are shown with a comparison of the performance time. Although more empirical studies should be conducted to reveal the relationship between the VPP measure and other PSFs, it is believed that the VPP measure provides evidence to quantitatively evaluate human performance variations and to cross-culturally compare the collected data.

► The VPP measure was developed to quantify how differently operators follow the procedures.
► Sources that cause variability of ways to follow a given procedure were identified.
► The VPP values for the scenarios are positively related to the scenario performance time.
► The VPP measure is meaningful for explaining characteristics of several PSFs.