Question: A machine produces metal rods used in an automobile suspension system. A random sample of 15 rods is selected, and the diameter is measured. The resulting data (in millimeters) are as follows:

8.24 8.25 8.20 8.23 8.24

8.21 8.26 8.26 8.20 8.25

8.23 8.23 8.19 8.28 8.24

(a) Check the assumption of normality for rod diameter

(b) Calculate the 95% two-sided confidence interval on mean rod diameter

(c) Calculate a 95% upper confidence bound on the mean. Compare this bound with the upper bound of the two-sided confidence interval.