# Question

Control chart for x and R are maintained on a process. After 20 preliminary subgroups each of size 3 are evaluated, you have the following data:
(a) Set up control charts using these data.
(b) Assume that the process exhibits statistical control. Estimate the process mean and standard deviation.
(c) Suppose that the quality characteristic is normally distributed with specifications at 275 = – 6. Estimate the fraction nonconforming produced by this process.
(d) How much reduction in process variability would be required to make this a Six Sigma process?

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