Mean µ and standard deviation are s1 and s2 from the two normal population. Drawn from the random sample of size n. a) we have to prove that the estimator is an unbiased. that is E(wX1bar+(1-w)X2bar) = w E(X1bar) +(1-w) E(X2bar) = w µ+ (1-w) µ =µ the estimator is unbiased estimator.