Gage R&R is one of the primary tools to estimate the variance in the measurements. As described in the previous table, it basically calculates repeatability and reproducibility. This combined value can then be used as an indication of the variation due to the measurement system. Mathematically, Gage R&R is represented as:

percent R&R = (σ Measurement system / σ Total) X 100

σ Measurement system = (σ2 repeatability+ σ2 reproducibility)1/2

The discrimination ratio refers to the number of distinct categories or classes that the measurement equipment can discern. A value of 2, for example, implies that the measurement system can be used only for attribute analysis where parts can be categorized into one group or the other. This can also be seen as the measure of the resolution of the measuring equipment. Resolution refers to the smallest change in a measured value that the measuring equipment can detect. For example, a digital stopwatch has two digits beyond the seconds...