Question

. Control charts for r and s are maintained on a process. After 25 preliminary subgroups each of size 3 are evaluated, you have the following data: į ; = 55.45 Įs; = 28.67 il i=1 (a) Set up the control charts using these data. (b) Assume that the process exhibits statistical con- trol. Estimate the process mean and standard deviation. (c) Suppose that the quality characteristic is nor- mally distributed with specifications at 2.25 4. 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?