A cutting operation. A machine tool in your plant is cutting an outside diameter. A sample of 4 pieces is taken near the end of each hour of production. Table 27.7
gives 
and s for the first 21 samples, coded in units of 0.0001 inch from the center of the specifications. The specifications allow a range of 
0.0002 inch about the center (a range of -2 to 2 as coded).
(a) Make an s chart based on past data and comment on control of short-term process variation.
(b) Because the data are coded about the center of the specs, we have a given target µ= 0 (as coded) for the process mean. Make an chart and comment on control of long-term process variation. What special x-type cause probably explains the lack of control of ?