11.57. Whenever xi and X2 are uncorrelated, then R 2

for the model ^(y) = a + 0ixi + 02X2 satisfies

=

'yxj + r yx2' t

^'s casc' draw a figure that portrays the variability in y, the part of that variability explained by each ofxi and X2, and the total variability explained by both of them together.