#37. a) Your first job is to determine all of the possible values for X-bar, and then calculate the probability for each value. For example, X-bar could be 25.0, but only if X1 = 25.0 and X2 = 25.0, and that happens with probability 0.04. so one value of X-bar is 25.0, with probability 0.04. X-bar could also be 32.5, but that only happens if X1 = 25.0 and X2 = 40.0, or X1 = 40.0 and X2 = 25.0. So the probability is 0.10 + 0.10 = 0.20. There are four more possible values for X-bar.
After you have all the values and probs for X-bar, then you can find the mean of the pdf by calculating E(X-bar) = Σ(X-bar)*Prob(X-bar)
#46. Remember that X-bar has a ?D(μpop, σ/sqrt(n)) distribution. Use that to answer the questions.
#47. Convert the problem to a z-score question, then use the z-table.
#49. The question is about the total time to sequentially grade 40 papers, i.e. ΣXi, where the Xi's refer to the times it takes to grade the individual papers. Translate that question to one about the the average time to grade 40 papers
#50. On your own on this one.
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