Webster Chemical Company produces mastics and caulking for the construction industry. The product is blended in large mixers and then pumped into tubes and capped. Management is concerned about whether the filling process for tubes of caulking is in statistical control. Several samples of eight tubes were taken, each tube was weighted, and the weights in the following table were obtained. Tube Number
Sample 1 2 3 4 5 6 7 8
1 7.98 8.34 8.02 7.94 8.44 7.68 7.81 8.11
2 8.33 8.22 8.08 8.51 8.41 8.28 8.09 8.16
3 7.89 7.77 7.91 8.04 8.00 7.89 7.93 8.09
4 8.24 8.18 7.83 8.05 7.90 8.16 7.97 8.07
5 7.87 8.13 7.92 7.99 8.10 7.81 8.14 7.88
6 8.13 8.14 8.11 8.13 8.14 8.12 8.13 8.14
a. Assume that only six samples are sufficient and develop the control charts for the mean and the range.
b. Plot the observations on the control chart and comment on your findings.