Evaluation of Selected Sensitivity Analysis Methods Based upon Applications to a Probabilistic Food Safety Process Risk Model: Case Study for Listeria monocytogenes
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Date
2003-12-01
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Abstract
With the emergence of large food safety risk models, there has also been a growing recognition of the need for sensitivity analysis of such models. Key questions that must be addressed in performing sensitivity analysis with food safety risk models include the following: What are the key criteria for sensitivity analysis methods applied to food safety risk assessment?; What sensitivity analysis methods are most promising for application to food safety and risk assessment?; and What are the key needs for implementation and demonstration of such methods?
Food safety risk assessment models are challenging because they typically include: (1) nonlinearities; (2) thresholds; (3) continuous, discrete, and categorical inputs; and (4) two-dimensional simulation of variability and uncertainty.
In June 2001, NCSU hosted a workshop on sensitivity analysis. Recommendations were made regarding a guideline document to assist practitioners in selecting, applying, interpreting, and reporting the results of sensitivity analysis. The workshop also supported the need for case studies with existing food safety risk models to demonstrate to practitioners how sensitivity analysis methods can be used and to evaluate various specific methods.
The two main purposes of this report are to: (1) evaluate sensitivity analysis methods; and (2) present an example of how sensitivity analysis can be applied to food safety risk assessment models and how the results can be presented and interpreted. This study included a review of existing methods, and a detailed series of quantitative case studies of multiple sensitivity analysis methods applied to Listeria monocytogenes model. Methods evaluated include local sensitivity analysis (e.g., nominal range sensitivity, differential sensitivity), global sensitivity analysis methods (e.g., linear regression, analysis of variance, and regression trees), and the graphical method of scatter plot. The report present example results and insights from the application of these methods of sensitivity analysis to the model.
The methods were compared and evaluated with regard to multiple criteria, including applicability, robustness of results, ability to rank and discriminate among inputs, and others. The guidance emerging from this research includes: (1) why and when to perform sensitivity analysis; (2) preparation of existing or new models to facilitate sensitivity analysis; (3) defining objectives and case study scenarios; (4) selection of methods; (5) general principles for application of methods; and (6) presentation and interpretation of results.
[This work was supported by a cooperative agreement with U.S. Department of Agriculture's Office of Risk Assessment and Cost-Benefit Analysis]
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Keywords
CART, food safety risk assessment, Listeria monocytogenes, Scatter Plots, sensitivity analysis, 2-D Monte Carlo anlysis, NRSA, DSA, ANOVA
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Degree
MS
Discipline
Civil Engineering
