The article from which the data in Exercise 1 was extracted also gave the accompanying strength observations for cylinders:

6.1 5.8 7.8 7.1 7.2 9.2 6.6 8.3 7.0 8.3 7.8 8.1 7.4 8.5 8.9 9.8 9.7 14.1 12.6 11.2 Prior to obtaining data, denote the beam strengths by X1,..., Xm and the cylinder strengths by Y1, . . . , Yn. Suppose that the Xi

’s constitute a random sample from a distribution with mean 1 and standard deviation s1 and that the Yi

’s form a random sample (independent of the Xi

’s) from another distribution with mean m2 and standard deviation s2

a. Use rules of expected value to show that is an unbiased estimator of 1