(20 points) Suppose a machine is manufacturing nails. As a quality control test, a random sample of 100 nails from the machine is selected. The mean length of the nails is found to be 9.1 inches and the standard deviation of the length of the nails is 0.19 inches. a. What must be assumed about the distribution of the length of the nails in order to be able to construct a confidence interval for the standard deviation of the length of the nails? b. Assume that we can construct a confidence interval for the standard deviation of the length of the nails. Construct and interpret a confidence interval for the standard deviation of the length of the nails at a 90% confidence level.
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In order to construct a confidence interval for the standard deviation of the length of the nails, we must assume that the distribution of the length of the nails is normally distributed. Show more…
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