A manufacturer produces piston rings for an automobile engine. It is known that ring diameter is normally distributed with σ = 0
.001 millimeters. A random sample of 15 rings has a mean diameter of x = 74.036 millimeters. (a) Construct a 99% two-sided confidence interval on the mean piston ring diameter.
(b) Construct a 99% lower-confidence bound on the mean piston ring diameter. Compare the lower bound of this confidence interval with the one in part (a).
