A machine produces metal rods used in an automobile suspension system. A random sample of 15 rods

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:

(a) Check the assumption of normality for rod diameter.
(b) Find a 95% two-sided confidence interval on mean rod diameter.