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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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E Uncertainty, Sensitivity, and Bayesian Methods
Pages 194-198

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From page 194...
... Uncertainties exist for many reasons, including randomness, incomplete knowledge with regard to phenomena, inaccuracies in determination of the values of quantities and parameters (e.g., a probability value) , high sensitivities of system performance to specific conditions, and omission of important factors (e.g., a basic event)
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From page 195...
... ; or • Repeated trials of an idealized thought experiment will lead to a distribution of outcomes for the variable, and thus this distribution is a measure of the aleatory uncertainties in the variable. The uncertainty is epistemic if • One is dealing with uncertainties in a deterministic variable whose true value is unknown; • Repeated trials of a thought experiment involving the variable will result in a single outcome, the true value of the variable; or • It is reducible (at least in principle)
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From page 196...
... For this reason and with clear documentation, the analysis or elicitation can be well defended. The implications of the different values the uncertain variable might take and their corresponding probabilities of being true can be propagated to the ultimate answer obtained concerning the risk level (see the discussion of uncertainty propagation below)
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From page 197...
... . BAYESIAN STATISTICAL ANALYSIS For risk assessment, the Bayesian approach offers important advantages: all kinds of evidence are used, uncertainty bands are narrower, and evaluating data with zero occurrences of events in N trials is straightforward.
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From page 198...
... Generalized forms of Bayesian inference developed in recent years provide ways of using such information in developing epistemic uncertainty distributions for risk model parameters. REFERENCES Apostolakis, G
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Key Terms

  • repeated trials
  • uncertainty propagation
  • risk analysis
  • uncertain variable
  • epistemic uncertainty

  • sensitivity analyses
  • ultimate answers
  • thought experiment
  • bayesian statistical
  • approximate estimate

  • true value
  • model parameters
  • particular measure
  • idealized thought
  • relative abundance

  • monte carlo
  • getting evidence
  • bayesian inference
  • treating uncertainty
  • carlo technique

  • ultimate risk
  • individual values
  • propagation below
  • developing epistemic
  • careful thinking

  • epistemic uncertainties
  • inverse probability
  • measure values
  • tive framework
  • tain factors


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