U(W) U(W2) pU(W1)+(1-p)U(W2) U[pWi+(1-p)W2l U(W) d WI pWi+(1-p)W2 W2 W 风险爱好者的效用函数风险爱好者的效用函数 W1 pW1 +(1-p)W2 W2 U(W) O W U(W1 ) U(W2 ) U[ pW1 +(1-p)W2 ] pU(W1 )+ (1-p) U(W2 )