The data in HW $(4)$ Data Excel file list electrical resistance measure values for $30$ samples of size $4$ that were

taken from ABC Chips, Inc.$$s computer chip$-$making process over a $15-$hour period.

a$)$ Compute the mean and range of each sample.

b$)$ Calculate the control limits and construct the X$-$Bar and R control charts, using the $30$ samples.

c$)$ Does the process appear to be in statistical control? Why or why not? What should be done if it is not

under control?