Any time you measure the results of a process, you will see some variation. This variation comes from several sources:

·    Differences between parts - there are always differences between parts made by any process.

·    Measurement system variability - any method of taking measurements is imperfect; thus, measuring the same part repeatedly does not result in identical measurements.

·    Other factors - can influence measurements.

Use Gage R&R Study (Expanded) to determine what portion of the variability in measurements may be due to the measurement system versus part-to-part variation. Measurement system variability includes variation due to the gage, operator (optional), and a maximum of eight additional factors (optional). All factors can be fixed or random, and crossed or nested. The design can be balanced or unbalanced.

In a Gage R&R study, it is important that the measurements are done in a random order and that the parts selected provide a representative sample across the possible range of responses.

Three operators each measured the refractive properties of 22 different glass parts at two different stations. Analysts want to look at the variability due to part, operator, and station.

Data: Refraction.MTW (available in the Sample Data folder).