The file P20_10.xlsx contains the breaking strengths (measured in pounds) of randomly selected pieces of a certain welded material. In particular, these data consist of 25 subsamples of 5 observed breaking strengths each. The target breaking strength of this welded material is 300 pounds.

a. Generate and interpret X and R charts for the given data. Does this production process appear to be in control?

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

c. If the process is out of control, which subsamples could be eliminated to achieve in-control behavior in the R chart? Why might it be legitimate to eliminate these subsamples?