Show that the estimator given by (13.104) is design-unbiased for 2 i ; that is, Ed(2 i

Show that the estimator given by (13.104) is design-unbiased for μ2 i ; that is, Ed(ˆμ2 i ) = μ2 i . [Hint: Use the index set Ii ; see a derivation below (13.103).]