2.42. Let X1,X2, . . . ,Xn be i.i.d. random variables with (unknown) mean u and variance 02. We want to estimate [1 and 02. Show that 53,, d=ef (X 1 + - - - + Xn) has expectation p. and 2:: 1 (X ,- 3J2 has expectation 02. (Note: an 1, not n.) These are called unbiased estimates of u and 02, resPectively