Group Decision Making: How to Obtain Representative Group Judgments from Individual Judgments

Introduction

Decision making is not like measuring something on a scale because it involves human values that are intangible. We make judgments about these intangibles in two ways. One is intuitive and spontaneous and may be the result of long and profound experience. The other is reasoned and deliberative. It relies on both intelligence and the ability to think logically about the many factors that are involved in a decision and the outcome of the interaction and feedback among these factors. It is known that intelligence is not the only factor that determines whether a person is a good thinker and decision maker. Either way by itself may lead to wrong estimates of relations, but usually we use them together to synthesize a richer judgment that is likely to be the wiser way to make a decision. We cannot make a decision without knowing how important each person’s value is in each particular decision and how to combine them all in the appropriate way to get the best decision. How to measure and prioritize these values and trade them off is a primary concern of decision making. In this chapter we delve into the details of the Analytic Hierarchy Process (AHP), including a validation example, and alerting the reader about the stimulus-response derivation of the 1–9 scale, why we should only compare a few elements at a time and the role of inconsistency in that determination. Finally, why the geometric mean, not the arithmetic mean is the only way to combine individual judgments into a group judgment is discussed along with how, when necessary, to include the priorities of the individuals because of their power and expert knowledge.