I have a terrible teacher and have to teach myself out of the book and don't understand this. 1. The problem statement, all variables and given/known data Male verbal IQs 117 103 121 112 120 132 113 117 132 149 125 131 136 107 108 113 136 114 Female Verbal IQs 114 102 113 131 124 117 120 90 114 109 102 114 127 127 103 Denote the male values by X1, X2...Xm and female values by Y1, Y2...Yn. Suppose that the Xi's constitute a random sample froma distribution with mean mu_1 and standard deviation sigma_1 and the Yi's form a random sample distribution (independent from the Xi's) with mean mu_2 and standard deviation sigma_2. a.) Use rules of expected vale to show that Xbar - Ybar is an unbiased estimator of mu_1 - mu_2. 3. The attempt at a solution I know that bias is the difference between the Expected value of the estimator and the value of the parameter. However, I am completely lost on how I can figure this out if I don't know the true means of the IQs. E(Xbar - Ybar) = E(Xbar) - E(Ybar) = (1/m)(X1+X2+...Xm) - (1/n)(Y1+Y2+...Yn) I have no idea what this means or where to go.