Elicitation for food microbial risk assessment: a probabilistic approach extending Risk Ranger proposal

Résumé

Ross and Sumner (2002) proposed a convenient tool, Risk Ranger, for early-stage risk assessment of microbial hazards in food systems. The authors describe the tool as being a simple way of comparing and classifying food-related risks and highlighting main factors that contribute to food safety. The output of the tool is a risk score based on answers to 11 questions. The objective of this work was to extend Risk Ranger towards a probabilistic version, distinguishing uncertainty and variability. For each question, we propose an elicitation procedure where the expert is asked for two quantiles to assess variability. Experts are also asked on their degree of confidence for the given quantiles to incorporate an uncertainty level. The new tool, also an Excel worksheet, allows the expert to check graphically, almost instantly, the uncertainty and variability of the variable of interest from the elicited quantiles and then to interactively modify them according to his/her view.