Influence Diagrams

The medical profession leads physicians and, in general, healthcare personnel to frequently face delicate situations that require accurate and careful decision making. The utilization of decision-support models is necessary to improve the decision-making process and to identify the optimal policy. The models allow unveiling of the decisions to be taken, their consequences, and the uncertain events that are involved in the problem. Influence diagrams are graphical tools for the representation and solution of decision-making problems. By representation, one means the identification of the decision-making problem elements. In particular, an influence diagram reveals the probabilistic dependences among the uncertain quantities and the state of information at each decision stage. By solution, one means the determination of the preferred alternative (best strategy selection) given the state of information. Influence diagrams grant decision makers the possibility of representing complex decision-making problems in a thorough albeit compact fashion. It is this strength over other representation techniques that has made the use of influence diagrams widespread in medical applications. This entry is organized as follows. It provides a description of influence diagrams by means of a sample medical example. The analysis of nodes and arcs of influence diagram follows. The discussion of the properties and levels of influence diagrams is offered next. The discussion is a prelude to a synthetic description of influence diagram solution algorithms. The relationship between influence diagrams and decision trees, and a brief mention about other graphical representation techniques, concludes the entry.