It is often assumed that measurements are exact, and frequently the analysis and conclusions are based upon this assumption. An individual may fail to realize there is variation in the measurement system which affects the individual measurements, and subsequently, the decisions based upon the data. Measurement system error can be classified into five categories: bias, repeatability, reproducibility, stability and linearity.
One of the objectives of a measurement system study is to obtain information relative to the amount and types of measurement variation associated with a measurement system when it interacts with its environment. This information is valuable, since for the average production process, it is far more practical to recognize repeatability and calibration bias and establish reasonable limits for these, than to provide extremely accurate gages with very high repeatability. Applications of such a study provide the following:
A criterion to accept new measuring equipment
A comparison of one measuring device against another
A basis for evaluating a gage suspected of being deficient
A comparison for measuring equipment before and after repair
A required component for calculating process variation, and the acceptability level for a production process
Information necessary to develop a Gage Performance Curve
source of Measurement System Variation: Analysis of measurement systems
