The fence of a saw is set so that it automatically cuts 2-by-4 boards into 96-inch lengths needed to produce prefabricated homes. To ensure that the lumber is cut properly, three pieces of wood are measured after each 100 cuts are made. The measurements in inches for the last 40 samples were recorded.
a. Do these data indicate that the process is out of control?
b. If so, when did it go out of control? What is the likely cause: level shift, instability, trend, or cycle?
c. Speculate on how the problem could be corrected.