EXAMPLE 12.10 Capability of a Lab-Testing Process

CASE 12.1 In Examples 12.2 and 12.7 (pages 605–607 and 621), we found the estimates for the mean and standard deviation:

In this application, the upper specification limit was set to 50 minutes. We estimate the one-sided upper capability index to be

The estimated capability index is considerably less than 1. As can be seen from Figure 12.13 (page 620), this reflects the fact that the process mean is close enough to the upper specification limit to result in a high percent of unacceptable outcomes.