Samples of I1 = 6 items are taken from a process at regular intervals. A normally distributed Quality characteristic is measured and I" and R values are calculated for each sample. After 50 subgroups have bean analyzed, we have: d) 1531 xi = 2:00" and 1531 R: = 20*] Compute the control limits for the f and R control charts. (Hint: f'nst compute the grand mean f and the average range 1?} Assume that all points on both charts plot within the control limits {i.e. the f and R charts are in stat'??cal control]1 give an estimate of the {unknown} process mean pt and an estimate of the {unknown} process standard deviation tr. If the speci?cation limits on this product are 41 :I: 5.0. what are your conclusions regarding the ability of the process to produce items conforming to specifications? That is, estimate the potential capabilityr of the process CF, and the actual process capabilityr CM. Assuming that if an item exceeds the upper speci?cation limit it can be reworked, and if it is below the lower speci?cation limit it must scrapped, what percentage scrap and rework is the process now producing? (Hint: Use the normal distribution and the normal curve areas to compute this percentage). Make suggestions as to how the process performance could be improved.

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