Question

1. Samples of n = 6 items each are taken from a process at regular intervals. A quality characteristic is measured, and x-bar and R values are calculated for each sample. After 50 samples, we have

1. Compute control limits for the x-bar and R control charts.
2. All points on both control charts fall between the control limits computed in part (a). What are the natural tolerance limits of the process?
3. If the specification limits are 41 ± 5.0, what are your conclusions regarding the ability of the process to produce items within these specifications?
4. Assume that an item can be reworked if it exceeds the upper specification limit, and must be scrapped if it is below the lower specification limit. What percent scrap and what percent rework is the process producing?
5. Make suggestions as to how the process performance could be improved.

Answer 1

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