1. Samples of n = 4 items are taken from a manufacturing process at regular intervals. A normally distributed quality characteristics is measured and (Subgroup means) and s (Subgroup standard deviations) values are calculated for subgroup. After 50 sub groups havebeen analyzed, we have

1. Compute the control limit for the and s charts
2. Estimate the process standard deviation
3. Assume that all points on both charts plot within the control limits. What are the natural tolerance limits of the process?
4. It the specification limits are 19, what are your conclusion regarding the ability of the process to produce items conforming to specifications?
5. Assuming that if an item exceeds the upper specification limit it can be reworked and if it is below the lower limit it must be scrapped, what percent scrap and rework is the process now producing?
6. It the process were centered on at u = 19.0, what would be the effect on the percent scrap or rework?