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6. Let X1, X2, . . . be a random sample of independent, identically distributed variables with Xi ~ Ber(0), where e E (0, 1). Suppose we are interested in parametric estimators of Var(Xi) = g(0) = 0(1 -0). Let Xn be the sample mean of the random sample. (a) Find E[Xn]. Is Xn an unbiased estimator of 0 ? (b) Find E[Xn(1 - Xn)]. Is Xn(1 - Xn) an unbiased estimator of g(0)