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8. Samples of n=6 items each are taken from a process at regular intervals. A quality characteristic is measured, and X and R values are calculated for each sample. After 50 samples, we have: 50 50 EX, = 2000 and ER, = 200 Assume that the quality characteristic is normally distributed. a. Compute control limits for the X and R control charts. (10 pts.) b. All points on both control charts fall between the control limits on part (a). What are the natural tolerance limits of the process? (5 pts.) c. The specifications limits for this process are 41.0 1 5.0. Assuming that if an item exceeds the upper specification limit it can be reworked and if it is below the lower specification limit it must be scrapped, what percent scrap and what percent rework is the process producing? (10 pts.) d. Make suggestions as to how process performance could be improved. (5 pts.)