1、模型变换法 (3)f(xa)=ro+rx Var(s)-o;-o'(ro+rix) bo +bix ro+rix ro+rix:ro+rx i ro+riXi o+1X, ( ) ( ) ( )         2 0 1 0 1 2 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 2 2 1 ( ) = + + = + =         + + + + + + = + = = + r r x r r x r r x r r x r r x r r x b x r r x b r r x y r r x i i i i i i i i i i i i i i i i Var Var Var ( xi ) r r xi f 0 1 (3) = + 1、模型变换法