Showing papers by "Simon French published in 1997"

Decision Support Issues in RODOS: The Needs of Decision Makers

Abstract: RODOS will be used by a great variety of different decision makers from different backgrounds and with different skills and knowledge bases. In the early hours the users will be the plant management and local emergency planners; later, regional and national politicians and government officials will become involved. In addition, a great number of technical experts and advisors will interact with RODOS. In recent years, the CEC has sponsored a number of investigations and exercises to identify the support that the decision makers perceive that they need. The results of these are reported.

Uncertainty modelling, data assimilation and decision support for management of off-site nuclear emergencies

Abstract: Decision support systems for off-site nuclear emergency management must address the inherent uncertainty in an evolving and effectively unique accident sequence. From the earliest moments when an accidental release threatens, through any release, to the long term consequences arising from the resulting contamination, there are many uncertainties to be weighed in selecting countermeasure strategies. Many of these uncertainties can be reduced through the careful collection and analysis of variety of data. The ways in which data can and should be analysed to achieve this are discussed. It is argued that there is no place for ad hoc approaches in designing a complex decision support system to underpin emergency management. The analyses must fit together so that data and assessments of uncertainty can be passed from module to module in a seamless fashion.

Sensitivity analysis in statistical decision theory: A decision analytic view

Abstract: Sensitivity analysis provides a way to mitigate traditional criticisms of Bayesian statistical decision theory, concerning dependence on subjective inputs. We suggest a general framework for sensitivity analysis allowing for perturbations in both the utility function and the prior distribution. Perturbations are constrained to classes modelling imprecision in judgements The framework discards first definitely bad alternatives; then, identifies alternatives that may share optimality with a current one; and, finally, detects least changes in the inputs leading to changes in ranking. The associated computational problems and their implementation are discussed.

Probabilistic Data Assimilation within RODOS

Abstract: An outline of the uncertainty handling and data assimilation framework within a Bayesian frame is given, illustrated by its use within RODOS. Particular emphasis is paid to the need for compatible methodologies and data structures to hold uncertainty assessments throughout all the modules of a decision support system. Progress at developing techniques and modules is described: (i) to use belief nets to predict the source term when an accidental release threatens; (ii) to estimate the source term using a ring of gamma monitors at the periphery of the plant; and (iii) to estimate the source term from both near and more distant measurements. The management of uncertainties in the food chain modelling is briefly indicated. Finally, the issue of moving the basis of prediction from modelling approaches to databases of environmental measurements is discussed.

Issues In Supporting Intertemporal Choice

Abstract: Intertemporal decision making refers to contexts in which the consequences accumulate in stages over time. Attention is confined to cases in which the stages are discrete. The purpose of this paper is to highlight some of the anomalies between how people‘ should’ make and how they ‘do’ make intertemporal decisions: i.e. between findings in the normative and descriptive literatures. The paper indicates some of the framing issues which must be considered when trying to obtain a decision maker’s preferences, especially with respect to the way the questions are posed. The intention is to identify some of the bridges which need to be built between descriptive and normative ideas if decision makers are to be supported effectively in making intertemporal decisions.

Equity and MCDA in the Event of a Nuclear Accident

Abstract: Decision making on countermeasures in the event of a nuclear accident such as Chernobyl is complex. Many criteria are involved. Aside from obvious ones related to the direct effects of radiation, there are issues relating to psychological stress, public acceptability and the need to consider the longer term economics of the affected regions. Thus there are many ways in which multi-criteria decision analysis (MCDA) can provide insights and support to the decision makers. Decisions on countermeasures will be made, at least initially, in the face of considerable uncertainty and the interplay between equity and uncertainty in the evaluation of different countermeasure strategies is far from straightforward. Apparently reasonable approaches, which appear to treat different population groups equitably, can, on closer examination, have unreasonable effects. The paper describes the MCDA components in relation to equity judgements of a decision support system (RODOS) for such emergencies being built by a consortium of institutes within the European Union, Eastern Europe and the former Soviet Union.

Towards a constructive approach to act-conditional subjective expected utility models

Abstract: In structuring a decision problem under uncertainty, the uncertain environment may be affected by the choice of an act. In decision analysis, the decision maker provides subjective probabilities and utilities through separate elicitation processes, and then both components are combined together to give an index of his preference over decision alternatives. Based upon this conceptualisation of decision analysis, a constructive approach to act-conditional subjective expected utility theory is proposed. Two utility models have been addressed: the linear utility model and the weighted utility model.