You have just installed a new system that uses an interferometer to measure the thickness of polystyrene film. To control the thickness, you plan to measure three film specimens every 10 minutes and keep and s charts. To establish control you measure 22 samples of three films each at 10-minute intervals. Table 12.11 gives and s for these samples. The units are millimeters . Exercises 12.55 through 12.57 are based on this process improvement setting.
12.56 chart.
Interviews with the operators reveal that in Samples 1 and 10, mistakes in operating the interferometer resulted in one high-outlier thickness reading that was clearly incorrect. Recalculate after removing Samples 1 and 10. Recalculate UCL for the chart and add the new UCL to your chart from the previous exercise. Control for the remaining samples is excellent. Now find the appropriate center line and control limits for an chart, make the chart, and comment on control.
| Sample | Sample | ||||
| 1 | 848 | 20.1 | 12 | 823 | 12.6 |
| 2 | 832 | 1.1 | 13 | 835 | 4.4 |
| 3 | 826 | 11.0 | 14 | 843 | 3.6 |
| 4 | 833 | 7.5 | 15 | 841 | 5.9 |
| 5 | 837 | 12.5 | 16 | 840 | 3.6 |
| 6 | 834 | 1.8 | 17 | 833 | 4.9 |
| 7 | 834 | 1.3 | 18 | 840 | 8.0 |
| 8 | 838 | 7.4 | 19 | 826 | 6.1 |
| 9 | 835 | 2.1 | 20 | 839 | 10.2 |
| 10 | 852 | 18.9 | 21 | 836 | 14.8 |
| 11 | 836 | 3.8 | 22 | 829 | 6.7 |
film