Computer upgrades have a nominal time of 80 minutes. Samples of 5 observations each have been taken, and the results are listed below. Determine the upper and lower control limits for mean and range charts, and decide if the process is in control.
SAMPLE
1 2 3 4 5 6
79.2 80.5 79.8 78.9 80.5 79.7
78.8 78.7 79.4 79.4 79.6 80.6
80.0 81.0 80.4 79.7 80.4 80.5
78.4 80.4 80.3 79.4 80.8 80.0
81.0 80.1 80.8 80.6 78.8 81.1