The X̅-R charts in Figure 9.38 show

The X̅-R charts in Figure 9.38 show that while both operators R- Charts are in control, Operator 2 shows substantially more repeatability variability,i.e., the Operator 2 R-chart has much greater rangcs (X̅ = 2.5) than does the Operator 1 R-chart, where X̅ =1.0. Operator 2 is clearly having more difficulty in making consistent measurements than is Operator 1. The ̅ X chart for Operator 1 appears to have at least half of its points beyond the control limits. However , this is not bad because it shows that Operator 1 has the ability to discriminate aming the products. Operator 2 does not show that kind of discriminatory power because its control limits are spread apart so far,due to the large R values for Operator 2. Note that this is a somewhat different interpretation of an X̅-chart than the shewhart interpretation. While the center lines of the X̅-chart are fairly close, indicating decent reproducibility between operator, the center lines of the R-charts are quite different, thus indicating that Operator 2 is exhibiting greater repeatability problems.