Northern White Metals Corp. uses an extrusion process to produce various kinds of aluminum brackets. Raw aluminum ingots are forced under pressure through steel dies to produce long sections of a desired cross-sectional shape. These sections are then fed through an automatic saw, where they are cut into brackets of the desired length. NWMC operates for three shifts of 4 hours each day, and the saw is recalibrated at the beginning of each shift. This week NWMC is producing #409 brackets with a specifi ed cut length of 4 inches. Silvia Serrano, NWMC’s quality specialist, has recorded the lengths of 15 randomly chosen brackets during each half hour of today’s three shifts to get the following data:
| Batch | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| Hour | Bearing Diameters (mm) | ||||||||||||||
| 1 | 5.03 | 5.06 | 4.86 | 4.90 | 4.95 | ||||||||||
| 2 | 4.97 | 4.94 | 5.09 | 4.78 | 4.88 | ||||||||||
| 3 | 5.02 | 4.98 | 4.94 | 4.95 | 4.80 | ||||||||||
| 4 | 4.92 | 4.93 | 4.90 | 4.92 | 4.96 | ||||||||||
| 5 | 5.01 | 4.99 | 4.93 | 5.06 | 5.01 | ||||||||||
| 6 | 5.00 | 4.95 | 5.10 | 4.85 | 4.91 | ||||||||||
| 7 | 4.94 | 4.91 | 5.05 | 5.07 | 4.88 | ||||||||||
| 8 | 5.00 | 4.98 | 5.05 | 4.96 | 4.97 | ||||||||||
| 9 | 4.99 | 5.01 | 4.93 | 5.10 | 4.98 | ||||||||||
| 10 | 5.03 | 4.96 | 4.92 | 5.01 | 4.93 | ||||||||||
| 11 | 5.02 | 4.88 | 5.00 | 4.98 | 5.09 | ||||||||||
| 12 | 5.09 | 5.01 | 5.13 | 4.89 | 5.02 | ||||||||||
| 13 | 4.90 | 4.93 | 4.97 | 4.98 | 5.12 | ||||||||||
| 14 | 5.04 | 4.96 | 5.15 | 5.04 | 5.02 | ||||||||||
| 15 | 5.09 | 4.90 | 5.04 | 5.19 | 5.03 | ||||||||||
| 16 | 5.10 | 5.01 | 5.04 | 5.05 | 5.02 | ||||||||||
| 17 | 4.97 | 5.10 | 5.12 | 4.92 | 5.04 | ||||||||||
| 18 | 5.01 | 4.99 | 5.06 | 5.04 | 5.12 | ||||||||||
- (a) Construct an x chart to help Seth determine whether the production of 5-mm bearings is
in-control.
- Should Seth conclude that the process is in-control? Explain.
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