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The Theory of Rational Choice. The Theory of Rational Choice. A rational decision-maker chooses the best action according to her preferences, among the actions available to her. Set of available actions Preferences Complete Consistent (transitive) Rational Selfish.
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The Theory of Rational Choice A rational decision-maker chooses the best action according to her preferences, among the actions available to her. Set of available actions Preferences Complete Consistent (transitive) Rational Selfish
The Theory of Rational Choice Payoff function: associates a number with each action in such a way that actions with the higher number are preferred. a and bA u(a) > u(b) if and only if the decision-maker prefers a to b
The Theory of Rational Choice Example: A = {Coke, Pepsi, Sprite} = {C, P, S} Decision-maker prefers C to P and P to S • u(C)=3, u(P)=2, u(S)=1 Or • u(C)=10, u(P)=0, u(S)=-2
The Theory of Rational Choice Preferences Ordinal information v is another payoff function that represents the same preferences as u if v(c) > v(p) u(c) > u(p) Any monotonically increasing function of u represents the same preferences
The Theory of Rational Choice Example: u(C)=3, u(P)=2, u(S)=1 u(C)=3 > u(P)=2 > u(S)=1 f(x)=2*x v(x) = f(u(x)) v(C) = f(u(C)) = f(3)=6, v(P)=4, v(S)=2 v(C)=6 > v(P)=4 > v(S)=2
The Theory of Rational Choice The action chosen by a decision-maker is at least as good, according to her preferences, as every other available action. Example: If A={P,C} and she always chooses C If A’={P,C,S} and she chooses P • Inconsistent with the Theory of Rational Choice To be consistent she must choose C or S - See the Weak Axiom of Revealed Preference (WARP)