Gage Repeatability and Reproducibility (R&R)
Gage R&R is a statistical tool that measures the amount of variation in the measurement system arising from the measurement device and the operators.
%GRR = (σ_GRR / σ_Total) × 100
Where:
- Repeatability - Variation from the measurement device (same operator, same part)
- Reproducibility - Variation from different operators (different operators, same part)
- Total GRR - Combined repeatability and reproducibility variation
- Part Variation - Variation between different parts being measured
Study Setup
Gage R&R Results
Repeatability (EV)
Equipment Variation
Reproducibility (AV)
Appraiser Variation
Total GRR
Combined Variation
Part Variation (PV)
Part-to-Part Variation
Percentage of Variation
| Source | % Contribution | % Tolerance (if provided) |
|---|---|---|
| Repeatability (EV) | ||
| Reproducibility (AV) | ||
| GRR (EV + AV) | ||
| Part Variation (PV) | ||
| Total Variation | 100% |
Interpretation Guidelines
| %GRR | Measurement System Evaluation |
|---|---|
| < 10% | Excellent - Measurement system is acceptable |
| 10% - 30% | Marginal - May be acceptable based on importance of application |
| > 30% | Unacceptable - Needs improvement |
Practical Examples
Example 1: Excellent Measurement System
%GRR = 8%, %Tolerance = 15%
This measurement system is excellent and more than adequate for process control and analysis.
Example 2: Marginal Measurement System
%GRR = 22%, %Tolerance = 45%
This system may be acceptable for some applications but should be improved where possible.
Example 3: Unacceptable Measurement System
%GRR = 42%, %Tolerance = 85%
This system needs immediate improvement before it can be used for process control.