Gage R&R is used to study the precision of a measurement system and it can quantify the repeatability and reproducibility components of the measurement variation. A typical Gage R&R study generally involves 2-3 operators, taking measurements on 5-10 samples for 2-3 trials each.

Repeatability is the inherent variability of the measurement equipment. It is the variation across multiple trials, by the same operator, on the same part, using same measurement equipment. It is an assessment of the ability to get the same measurements repeatedly.

Reproducibility is the variation across different operators, on the same part, using the same equipment. It is an assessment of the ability to reproduce the measurement of another operator.

Interpretation
Gage R&R studies generally produce both numerical and graphical outputs. The following are guidelines on how to interpret those results.

Part sum of squares and P-value - If the variation for part is high and P-value is low, this indicates that variation is due to part differences and parts are distinctly distinguishable by operators.

Operator sum of squares and P-value - If the variation for (between) operator is low and P-value is high, this indicates high repeatability.

Interaction sum of squares and P-value - If there is low interaction between operator & part and P-value high, this indicates that different operators measure each part similarly.

Repeatability sum of squares - If the variation for (within) operator is low, this indicates low variation between operators and high reproducibility.

Total Gage R&R in %VarComp column
• > 9%, gage is not acceptable
• <= 9%, gage is acceptable
• <= 1%, gage is good

Total Gage R&R in %Study Var column
• > 30%, gage is not acceptable
• <= 30%, gage is acceptable
• <= 10%, gage is good

Number of distinctive categories - Must be at least 2 distinctive categories

Components of Variation Chart - Part-to-Part should contribute most to the total variation.

R chart by operator - An in-control chart indicates high repeatability.

Xbar Charts by operator - An out-of-control chart indicates part-to-part variation and low measurement system variation.

By Part Chart - A non-constant line indicates part-to-part variation.

By Operator - A flat line indicates reproducibility.

Operator*Part Interaction - Parallel lines indicate low operator*part interaction.