Question

We have two independent populations A and B, with means ji and p2 and variances o and ož, respectively. Parameter of interest is difference 0 = M1 – M2. To estimate the difference 0, we use Ô = X - Y, where X and Y are the sample means from the respective populations, based on samples of sizes ni, n2, respectively. Which of the following statements is true? A. E[@] = 0 and Var[@] = 0;/nı + o2/n2 B. E[O] # 0 and Var[@] = oỉ/nı tož/n2 C. ETÔ) = 0 and Var[@] = 01/nı - 02/12 D. E[0] # 0 and Var[@] = o{/nı - 02/12 E. none of the preceding

Answer 1

Note-for the variance part... covariance term is zero..hence the formula

Here two independent poolen Independent A T h = (x) E (2) = E(X74) ZEC) - E(T) di - M2 772 And rco) Žvcx-7) = v(7) + (7) म - Artha ootels in ni nz Itence (A) 28 the answer

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