Refer to Problem 15.
a. Find the margin of error, E.
b. Explain the meaning of E as far as the accuracy of the estimate is concerned.
c. Determine the sample size required to have a margin of error of 0.1 mm and a 90% confidence level.
d. Find a 90% confidence interval for μ if a sample of the size determined in part (c) yields a mean of 12.0 mm.