Other than normal control chart analyses, there is no specific numerical analysis or index for stability.
If the measurement process is stable, the data can be used to determine the bias of the measurement system.Also, the standard deviation of the measurements can be used as an approximation for the measurement system’s repeatability. This can be compared with that of the process to determine if the measurement system repeatability is suitable for the application.
Design of Experiments or other analytical problem solving techniques may be required to determine the prime contributors to the lack of measurement system stability.
Example – index for stability
To determine if the stability of a new measurement instrument was acceptable, the process team selected a part near the middle of the range of the production process. This part was sent to the measurement lab to determine the reference value which is 6.01. The team measured this part 5 times once a shift for four weeks (20 subgroups). After all the data were collected, X & R charts were developed
Analysis of the control charts indicates that the measurement process is stable since there are no obvious special cause effects visible
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source : Analysis of measurement systems
