to be assessed. Following Pratt et al. (1995), we define risk assessment as a decision-making technique that incorporates objective and subjective estimates of the probability of uncertain factors and identifies preferred actions with respect to multiple objectives (see Box 9.1).

BOX 9.1
Glossary of Risk Analysis Terms

Bayes theorem: a statistical rule for combining relative frequencies and subjective probabilities or prior information about the likelihood of certain future conditions.

Conditional costs and benefits: outcomes that can be expected given the occurrence of specific management actions or particular stochastic events.

Decision: an active or passive choice.

Harm: costs incurred as a consequence of specific hazards; a conditional payoff. For example, some Chesapeake Bay stakeholders would construe the establishment of a self-sustaining population of nonnative oysters as a harm related to exposure to the hazard of reversion.

Hazard: an action or event that has the potential to result in an undesired outcome. In the context of this study, a hazard occasioned by open-water aquaculture of triploid nonnative oysters is that reproductively competent oysters are released and the undesired outcome is that the nonnative oysters become invasive.

Likelihood: the probability that an outcome will occur given exposure to a hazard.

Multiple criteria decision analysis: procedures for evaluating alternative outcomes with respect to multiple objectives.

Objectives: goals of stakeholders.

Payoffs: conditional outcomes evaluated in terms of management objectives.

Probability and probability distributions: statistical descriptions of relative frequencies, often expressed in terms of expected value, variance, skewness, and kurtosis.

Relative frequency: the frequency of particular outcomes relative to the frequency of observed outcomes

Risk: the possibility of undesired outcomes being realized as a result of management action or natural variability. In the context of this study, a risk associated with openwater aquaculture of triploid nonnative oysters could be defined as the joint probability that some oysters might revert and that their progeny might become established in the Chesapeake Bay.

Risk analysis: synonymous with risk assessment.

Risk assessment: a decision-making technique that incorporates relative frequencies and subjective probabilities of uncertain factors and identifies preferred actions with respect to one or more objectives.

Risk management: the avoidance, mitigation, reduction, shifting, pooling, or buffering of risk.

Risk preferences: faced with a choice between an action that leads to a guaranteed payoff and an action that leads to an equal but uncertain payoff, the selection of a particular payoff by a decision maker. Most decision makers in most circumstances will select the certain payoff; they are said to be risk averse.

Stakeholder: any person, group, or organization interested in the management decision.

Subjective probabilities: estimates of the likelihood of events and their distribution based on expert judgment with limited historical or experimental observations.



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