Complete the following steps to interpret an expanded gage R&R study. Key output includes variability estimates, and graphs of the measurements and measurement variability.

Use the ANOVA table to identify which sources of variability are significant. The ANOVA table includes the following terms in the Source column:

- Part: The variation that is from the parts.
- Operator: The variation that is from the operators.
- Nested factors: The variation that is from nested factors. Two factors are nested when each level of one factor occurs with only one level of the other factor. For example, if two operators measure two different, but similar, sets of parts, parts are nested under operator, and is indicated by Part (Operator). In this case, if the average measurement of different parts by each operator varies greatly, then Part (Operator) will be a significant source of variability.
- Interaction terms, such as Part*Operator: The variation that is from an interaction. For example, an interaction exists when an operator measures different parts differently.
- Error or repeatability: The variation that is not explained by part, operator, or other terms in the model.

If the p-value for an interaction is 0.05 or higher, Minitab omits the interaction because it is not significant and generates a second ANOVA table without the insignificant interactions.

Use the variance components (VarComp) and %Contribution to assess the variation for each source of measurement error. The sources are as follows:

- Total Gage R&R: The sum of the repeatability and the reproducibility variance components.
- Repeatability: The variability in measurements when the same operator measures the same part multiple times.
- Reproducibility: The variability in measurements when different operators measure the same part at the various conditions defined by the other factors in the model. The Reproducibility term can be divided further into Operator, Operator*Part, and other main effects and interaction effects.
- Part-to-Part: The variability in measurements due to different parts. In addition to Part, other factors might be used to calculate part-to-part variation.

Ideally, very little of the variability should be due to repeatability and reproducibility. Differences between parts (Part-to-Part) should account for most of the variability.

The gage R&R graphs provide information about the measurement system.

- Components of variation graph
- Shows whether the largest of component of variation is part-to-part variation.
- R chart by operator
- Shows whether any points fall above the upper control limit.
- Xbar chart by operator
- Shows whether most points fall beyond the control limits.
- Measurements by a single factor
- Shows all measurements, arranged by one factor. This graph helps you visualize the differences between factor levels.
- Interaction plots
- Shows the interaction between two factors. An interaction occurs when the effect of one factor is dependent upon a second factor. This plot is the graphical analog of the F-test for an interaction term in the ANOVA table.