Samples of rock taken from various places in a proposed mine have been analyzed. For each sample, a €œrate of return€ number has been computed that represents the profit obtained (by selling the refined metal at the current market price) as a percentage of the cost of extraction. This measure reflects the difficulty in removing the ore, the difficulty in processing it, and the yield of the finished product, all in meaningful economic terms. You may assume that the samples were drawn at random and represent the conditions under which actual production would take place, if it is economically viable. Economic viability will require that the return be high enough to justify the costs of operation. For the 13 samples obtained, the rates of return were as follows:

a. Find the summary statistics: n, the average, the standard deviation, and the standard error. Write
a brief paragraph describing the situation as if you were explaining it to the board of directors.
b. Identify the population and the population mean. Why is the population mean important to the management and owners of the proposed mine?
c. Find the appropriate one-sided 99% confidence interval. Write a brief paragraph summarizing its meaning.
d. Write a brief paragraph outlining the situation and making recommendations on possible action to top management.

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8.1%, 6.2%, 19.8%,-4.3%, 5.1%, 0.2%,-10.4%, 11.8%, 2.0%, 4.7%,-32%, 8.9%,-6.2%