## Overview of the Decision Analytic Process

Decision analysis is a process in which a decision analyst and domain experts work together to construct a mathematical model of a decision. The model is called a decision model. A decision analyst, who is in some ways a psychoanalyst for people with decision problems, uses a set of techniques to assist an organization or an individual to construct the decision model. The decision analyst and the experts build a decision model and then use it to compute the expected utilities of the choices (two or more) that are available to the decision maker.

A decision analysis in biosurveillance or any domain is based on substantial information about the domain that can only be obtained from experts or literature review. In biosurveillance, the information basis of a decision analysis comprises knowledge about diseases, epidemics, and costs of treatments. The decision analyst must elicit this knowledge from experts and from published sources.

Figure 29.2 depicts the steps that a decision maker and a decision analyst follow to construct a decision model and then to analyze the model to produce insight about the decision.

Spike in Antidiarrheal Sales

Spike in Antidiarrheal Sales

Time

FIGURE 29.1 Rising sales of diarrhea remedies that triggered an alert (detection threshold set to one false-alarm per year).

Time

FIGURE 29.1 Rising sales of diarrhea remedies that triggered an alert (detection threshold set to one false-alarm per year).

1 Experts on decision theory know that dollar amounts do not map linearly onto a utility scale. For small dollar amounts such as a \$10 bet with a \$20 payout, however, they often do.

Building a decision model is an iterative process. The analyst and experts construct a first draft, examine it, and then refine it based on new insights about the factors influencing the decision. Usually, regular, short consultations work best. Between these consultations, the decision analyst refines the model and prepares questions for the decision maker. The decision analyst may read textbooks to become familiar with the terminology and the important factors relevant to the decision. A decision analyst may tape record the sessions with the decision maker because it is often hard to process all the knowledge that the decision maker provides during a meeting. The decision analyst may organize brainstorming sessions with experts who are not directly involved in building the model to confirm that no aspect of the decision problem has been overlooked.

The products of a decision analysis are (1) a base-case analysis, which is the decision model configured using the best estimates of the various parameters that go into the model, and (2) a sensitivity analysis of the effects of varying parameters over a range that spans the uncertainty that the decision maker has about the exact values of those parameters. The sensitivity analysis demonstrates how robust (or fragile) the decision recommended by the model is to the imprecision of knowledge about the domain (e.g., the uncertainty about the cost of a boil-water advisory).

 Identify the problem