Six samples of five observations each have been taken of 80 kg concrete slabs produced by a machine, and the results are displayed below.
a. Using factors from Table 10-2, determine the upper and lower control limits for sample mean and range, and decide if the process is in control.
b. A new sample results in the following slab weights: 81.0, 81.0, 80.8, 80.6, and 80.5. Use the control limits determined in part a to decide if the process is still in control.