ABSTRACT
Herbert Simon, one of the management scholars, considers Decision Making (DM) as the essence of management. In his opinion, management is nothing but a decision, and a successful manager can be a successful decision maker. Decisions can be divided into two main categories according to different criteria: planned and unplanned decisions, and individual and group decisions. The importance of group decision is mentioned for five reasons: the issue of legitimacy; the quality of the decision; innovation; the lack of information; and morale. Although group DM has many effects on the organization, it is more appropriate in some situations if decisions are taken individually. A model is a pattern taken from reality and shows the relationships between the variables and can be used to predict the decision. By a model, the effects of different changes can be measured quickly and accurately, and the decision maker will be informed of their outcomes without risk or with risk.
