Multiple Choice Question A random sample of size n1 = 16 is selected from a normal population with mean 75 and variance 288. A second random sample of size n2 = 9 is selected from a normal population with mean 80 and variance 162. Assume that the random samples are independent. Let X, and X2 be the respective sample means. Find the probability that X1 + X2 is larger than 156.5. A. 0.5987 B. 0.4013 C. 0.6231 D. 0.4235 E. none of the preceding Multiple Choice Question Let X1, ..., X7 be a random sample from a population with mean / and variance o Consider the following estimators for /: Xit . . . + XT 2X1 - X6 . . . + X4 7 - 2 2 Are these estimators unbiased (i.e. is their expectation equal to #)? A. Both estimators are unbiased. B. Both estimators are biased. C. Only the second is unbiased. D. Only the first is unbiased. E. Insufficient information