Piston Rings for an Automotive Engine Are Produced by a Forging

Multiple Choice

Piston rings for an automotive engine are produced by a forging process.We monitor the inside diameter of the rings manufactured by this process using an and an s control chart.Samples of size 4 are taken at regular intervals,and the sample means and standard deviations are computed and plotted on the charts in time order.The overall mean of the sample means is 73.812 millimeters,and the mean of the sample standard deviations is 0.022 millimeters.The control chart constants are (partially) reproduced below. What is the lower control limit for the s chart?

A) -0.066 millimeters
B) 0 millimeters
C) 0.020 millimeters
D) 0.022 millimeters