10-15. Verify that if X1, . . . ,Xn depicts a random sample from a population for which both E(Xk) and V(Xk) exist, then 1n

ni

=1 Xk i is a consistent estimator of E(Xk). Use this result to demonstrate that S2 1

= 1n

ni

=1 (Xi − X)2 is a consistent estimator of σ2.