Continuing the previous problem, managers have made an adjustment that they hope will improve the functioning of this process. The file P20_07.xlsx contains 25 subsamples of 4 observations each on selected bolt lengths, taken after the production process was modified.

a. Generate and interpret X and R charts for the given data. Which control limits do you believe are most appropriate? Explain. Does this production process appear to be in control now?

b. Are there any other indications that the given process may be out of control now? If so, explain

c. What advice would you give to the operators of this production process based on your analysis of the latest sample information?