Control charts for x and R are maintained for an important quality characteristic. The sample size is n= 7; x and R are computed for each sample. After 35 samples we have found that

(a) Set up x and R charts using these data.
(b) Assuming that both charts exhibit control, estimate the process mean and standard deviation.
(c) If the quality characteristic is normally distributed and if the specifications are 220  35, can the process meet the specifications? Estimate the fraction nonconforming.
(d) Assuming the variance to remain constant, state where the process mean should be located to minimize the fraction nonconforming. What would be the value of the fraction nonconforming under these conditions?

35 35 =7,805 and R = 1,200