Measurement Systems Analysis

typically an operator, but can be thought of more generically as any condition that could affect the measurements. For example, with an automated process, condition might be a set-up procedure or an environmental condition such as temperature. A condition represents a potential nuisance source of variation.

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

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

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

the variation resulting from repeated measurements taken on the same part with the same gauge by the same operator. Repeatability is the gauge or equipment variation. This is also called test-retest variation.

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

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