Combining Expert Judgments for Environmental Risk Analysis

• Activity Number: 55
• Type: Invited
• Date/Time: Monday, August 12, 2002 : 8:30 AM to 10:20 AM
• Sponsor: Cmte on Energy Statistics
• Author(s): James Hammitt*+
• Affiliation(s): Harvard University

Abstract

Models used for estimating risks of environmental impact from energy systems and other technologies rely on parameter estimates obtained using either informal or formal expert judgments. Models using expert judgments can be sensitive to two problems: biases in experts coding their knowledge into probability distributions (such as overconfidence bias), and the typically uncertain degree of dependence in judgments between experts (e.g., each expert's judgment combines his reading of a common scientific literature and his own experience and interpretations). We analyze the properties of two state-of-the-art methods for combining expert judgments: the classical method developed by Roger Cooke and colleagues at Delft University of Technology and the copula method developed by Robert Clemen and colleagues at Duke University. We compare the methods mathematically and by evaluating their performance on synthetic and actual expert judgment data sets.