4.6 In the notation of the previous exercise, assume that 1r1, . . . , sir\" are independent random variables with common mean 7r and com mon variance 72w(1 7r). Show that, unconditionally, E(Y) = m,7r var(Y) = m,7r(1 7r){1 + (m 1)72} Deduce that 0 g T2 S 1, so that var(Y) 2 m,1r(1 7r)