Measurement System Analysis is the most fundamental step for use of other methods like DOE, SPC, etc.

Some definitions:

Measurement - is the assignment of values to material things to represent the relations among them with respect to particular properties.

Gage = any device used to obtain measurements.

Measurement System - is then the collection of instruments , gages, standards, methods, fixtures, software, personnel, environment and assumptions used to quantify a unit of measure.

GRR or Gage R&R - the combined estimate of measurement system repeatability and reproducibility.


During analysis we calculate many items like linearity, bias, repetability, reproducibility, provide graphical analysis...The most common index number for measurement system capability is so called GRR.

When GRR > 30% of tolerance or process variability, the gage must not be used!!!