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Risk of Vessel Accidents and Spills in the Aleutian Islands Designing a Comprehensive Risk Assessment - Special Report 293 (2009) / Chapter Skim
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C Expert Judgment
Pages 182-188

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From page 182...
... Expert opinion, in contrast to factual information, is a judgment or a belief that, at least in the mind of the receiver of the opinion, is based on uncertain information or limited knowledge. The primary reason for eliciting expert opinion is to deal with uncertainty with regard to selected technical issues.
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From page 183...
... • Aggregating the opinions of multiple experts tends to yield more accurate results than using the opinion of a single expert. • Mathematical methods of aggregation are generally preferable to behavioral methods for reaching consensus.
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From page 184...
... A facilitator can directly address any biases. For example, representativeness bias involves replacing a careful evaluation of the available information with quick conclusions based on partial information or allowing irrelevant information to affect one's conclusions.
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From page 185...
... CONTROLLING UNINTENTIONAL BIAS IN USING EXPERT OPINION One of the most important concerns associated with the use of a consensus expert judgment process is that of unintentional bias. In the subjective process of developing probability distributions, strong controls are needed to prevent bias from distorting the results (i.e., to prevent derivation of results that fail to reflect the team's state of knowledge)
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From page 186...
... • They have a need to structure the situation, which leads them to imagine patterns even when none exist. • They are fairly accurate at judging central tendency, especially the mode, but may significantly underestimate the range of uncer tainty (e.g., in half the cases, people's estimates of 98 percent intervals fail to include the true values)
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From page 187...
... A number of studies have shown that normative experts (whose domain knowledge is critical) can generate appropriate probability distributions but that substantive experts require significant training and experience or assistance (such as that provided by a facilitator)
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From page 188...
... 1988. A Critique of Current Practice for the Use of Expert Opinions in Probabilistic Risk Assessment.
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Key Terms

  • probability distributions
  • expert judgment
  • subjective probability
  • potential biases
  • expert judgments

  • expert opinions
  • normative experts
  • unintentional bias
  • central tendency
  • allowing irrelevant

  • bias involves
  • technique found
  • multiple expert
  • analysis team
  • expertise refers

  • substantially improved
  • subjective estimation
  • simple models
  • developing probability
  • experts require

  • ignores prior
  • prevent bias
  • widely documented
  • opinion involve
  • generate appropriate

  • evidence considered
  • substantial evidence
  • careful evaluation
  • concerns associated
  • estimating probability


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