GR&R

ANOVA gauge R&R (or ANOVA gauge repeatability and reproducibility) is a measurement systems analysis technique that uses an analysis of variance (ANOVA)random effects model to assess a measurement system.

NOVA gauge R&R measures the amount of variability induced in measurements by the measurement system itself, and compares it to the total variability observed to determine the viability of the measurement system. There are several factors affecting a measurement system, including:

• Measuring instruments, the gauge or instrument itself and all mounting blocks, supports, fixtures, load cells, etc. The machine's ease of use, sloppiness among mating parts, and, "zero" blocks are examples of sources of variation in the measurement system. In systems making electrical measurements, sources of variation include electrical noise and analog-to-digital converter resolution.

• Operators (people), the ability and/or discipline of a person to follow the written or verbal instructions.

• Test methods, how the devices are set up, the test fixtures, how the data is recorded, etc.

• Specification, the measurement is reported against a specification or a reference value. The range or the engineering tolerance does not affect the measurement, but is an important factor in evaluating the viability of the measurement system.

• Parts or specimens (what is being measured), some items are easier to be measured than others. A measurement system may be good for measuring steel block length but not for measuring rubber pieces, for example.

There are two important aspects of a Gauge R&R:

• Repeatability: The variation in measurements taken by a single person or instrument on the same or replicate item and under the same conditions.^[1]
• Reproducibility: the variation induced when different operators, instruments, or laboratories measure the same or replicate specimen.^[1]