The following definitions describe the terms used in a gage R&R study.

Gage

any device used to obtain measurements, for example, a micrometer or a gasket thickness gage.

Condition

typically an operator, but can be thought of more generically as any condition affecting the measurements. For example, with an automated process, condition might be a set-up procedure or an environmental condition such as temperature. For the remainder of this appendix, condition is referred to as operator.

Trial

a set of measurements on all parts taken by one operator. Multiple trials help separate the gage variability (repeatability) from the variability contributed by operators (reproducibility).

Part

the item that is measured, for example, a gasket. The parts selected should represent the entire operating range (variability) of the process.

Measurement System

the complete process used to obtain measurements. This includes people, gages, operations, and procedures.

Repeatability

the variation resulting from repeated measurements taken on the same part with the same gage by the same operator. Repeatability is the gage or equipment variation.

Reproducibility

the variation in the average of the measurements resulting when different operators using the same gage take measurements on the same part. Reproducibility is the operator-to-operator variability.