The graphic representation of the alternatives in a decision making problem which summarizes all the possibilities foreseen by the decision maker. For instance, suppose we are given the below written problem.
A physician should choose between two treatments. The patient is known to have one of the two diseases but the diagnosis is not very certain. A thorough examination of the patient was not able to resolve the diagnostic uncertainty. The best which can be said is that the probability which the patient has disease A is p. An easy decision tree for the problem is shown in the figure drawn below.