Quality and Reliability Methods - SAS

Chapter 8 Assess Measurement Systems 131
Measurement Systems Analysis Platform Options
Classes of Process Monitors
In order to understand the System and Classification parameters, you must first understand the Monitor
Classification Legend.
Figure 8.6 Monitor Classification Legend
This legend describes the following classifications: First, Second, Third, and Fourth Class. Each
classification indicates the following:
• the corresponding Intraclass Correlation values
• the amount of process signal attenuation (decrease)
• the chance of detecting a 3 standard error shift within 10 subgroups, using Wheeler’s test one or all four
tests
Wheeler (2006) identifies four detection tests known as the Western Electric Zone Tests. Within the Shift
Detection Profiler, there are eight tests that you can select from. The tests that correspond to the Wheeler
tests are the first, second, fifth, and sixth tests.
Effective Resolution
The Effective Resolution report helps you determine how well your measurement increments are working.
You might find that you need to add or drop digits when recording your measurements, or your current
increments might be effective as is. Note the following:
• The Probable Error calculates the minimum value of the median error of a measurement.
• The Current Measurement Increment reflects how many digits you are currently rounding to and is
taken from the data as the nearest power of ten. This number is compared to the Smallest Effective
Increment, Lower Bound Increment, and Largest Effective Increment. Based on that comparison, a
recommendation is made.
• Large measurement increments have less uncertainty in the last digit, but large median errors. Small
measurement increments have small median errors, but more uncertainty in the last digit.