Give an informal argument to show that if Y =

Xo'Y + e is a correct model, then the value of Cp should be around p.

Provide a formal argument for this fact. Show that if (n - s) > 2, then E(Cp ) = p + 2(s - p)/(n - s - 2). To do this you need to know that if W rv F(u,v,O), then E(W) = v/(v - 2) for v > 2. For large values of n

(relative to sand p), what is the approximate value of E(Cp )?