For example, several operators measure the diameter of screws to ensure that they meet specifications. A gage R&R study (
) indicates whether the inspectors are consistent in their measurements of the same part (repeatability) and whether the variation between inspectors is consistent (reproducibility).Percentage of process variation | Acceptability |
---|---|
Less than 10% | The measurement system is acceptable. |
Between 10% and 30% | The measurement system is acceptable depending on the application, the cost of the measurement device, cost of repair, or other factors. |
Greater than 30% | The measurement system is not acceptable and should be improved. |
Reference: Automotive Industry Action Group (AIAG) (2010). Measurement Systems Analysis Reference Manual, 4th edition.
Percentage of variance components | Acceptability |
---|---|
Less than 1% | The measurement system is acceptable. |
Between 1% and 9% | The measurement system is acceptable depending on the application, the cost of the measurement device, cost of repair, or other factors. |
Greater than 9% | The measurement system is not acceptable and should be improved. |
AIAG also states that the number of distinct categories into which the measurement system divides process output should be greater than or equal to 5.