Control charts for x and R are maintained on the tensile strength of a metal fastener. After 30 samples of size n= 6 are analyzed, we find that

(a) Compute control limits on the R chart.
(b) Assuming that the R chart exhibits control, estimate the parameters µ and σ.
(c) If the process output is normally distributed, and if the specifications are 440 + €“ 40, can the process meet the specifications? Estimate the fraction nonconforming.
(d) If the variance remains constant, where should the mean be located to minimize the fraction nonconforming?

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ΣΧ, 12, 870 and Σ R 1350