Measurement System Analysis
Average & Range method
Quality assurance teams must prove their measurement equipment is reliable before trusting the data it produces. A Gage R&R (Measurement System Analysis) calculator evaluates repeatability and reproducibility using the average and range method. By determining the percentage of study variation and the number of distinct categories, engineers can confidently validate whether a testing instrument is adequate for production control.
Repeatability is the variation observed when one operator measures the same part multiple times with the same gage. Reproducibility is the variation observed when different operators measure the same part using the same gage.
According to AIAG standards, a total Gage R&R variation under 10% is considered excellent. Between 10% and 30% may be acceptable depending on the application and cost. Above 30% means the measurement system is unacceptable and needs improvement.
The ndc indicates how many non-overlapping groups the measurement system can distinguish within the process variation. A reliable measurement system requires an ndc of 5 or greater.
Evaluating against tolerance (%Tolerance) is critical when the gage is used for final inspection (sorting good parts from bad). Evaluating against total variation (%Study) is used when the gage is for process control.