# Measurement System Analysis (MSA) Key Terms & Definitions

Written by

Gauge R & R Study: Measurement System Analysis (MSA) of the Gage R&R variety is used to assess how well a variable (continuous) measurement system is performing.

Resolution (or discrimination):  The smallest division on the gauge’s scale or the smallest difference in reading that can be displayed on a measuring instrument’s display is called resolution (or discrimination). The smaller measurement it can record, the higher the resolution.

Bias or accuracy: The variance between the average of the observed values and the standard deviation is known as bias or accuracy or actual value.

Linearity: The gauge must be consistent over its whole range to be considered linear.

Stability: Stability is the gauge’s continued constancy throughout time. When the same operator measures the same unit with the same measuring tools over a prolonged period of time, stability is seen if the observed values remain the same.

Precision: The variance between repeated observations of the same unit that is either caused by the operator (Reproducibility) or by the equipment is known as precision (Repeatability).

Reference Value: The theoretically or agreed upon correct value of the characteristic being measured, traceable to some standard

Repeatability: Repeatability is the variation between successive measurements of the same part, same characteristic, by the same person using the same gauge.

Reproducibility: Reproducibility is the difference in the average of the measurements made by different people using the same instrument when measuring the identical characteristic on the same pieces.