Mounting-hole distances. Figure 27.10 (page 27-23) displays a record sheet for 18 samples of distances between mounting holes in an electrical meter. The data file adds  and s for each sample. In Exercise 27.16, you found that Sample 5 was out of control on the process-monitoring s chart. The special cause responsible was found and removed. Based on the 17 samples that were in control, what are the natural tolerances for the distance between the holes?

Exercise 27.16:

Mounting-hole distances. Figure 27.10 reproduces a data sheet from the floor of a factory that makes electrical meters.8 The sheet shows measurements on the distance between two mounting holes for 18 samples of size 5. The heading informs us that the measurements are in multiples of 0.0001 inch above 0.6000 inch. That is, the first measurement, 44, stands for 0.6044 inch. All the measurements end in 4. Although we don't know why this is true, it is clear that in effect the measurements were made to the nearest 0.001 inch, not to the nearest 0.0001 inch. Calculate  and s for the first two samples. The data file contains  and s for all 18 samples. Based on long experience with this process, you are keeping control charts based on µ= 43 and σ= 12.74. Make s and  charts for the data in Figure 27.10 and describe the state of the process.

FIGURE 27.10: