Gage R&R Study

Use a gage R&R study to assess the repeatability and reproducibility of a measurement system.

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In This Topic

Crossed gage R&R study
Nested gage R&R study

Crossed gage R&R study

Use a crossed gage R&R study to assess the variation in your measurement system when every operator measures every part in the study. To perform this study, you must have a balanced design with random factors.

For example, an engineer selects 10 parts that represent the expected range of the process variation. For the study, 3 operators measure the 10 parts, 3 times per part, in random order. To see an example, go to Minitab Help: Example of Crossed Gage R&R Study.

Data considerations

Select parts from the entire range of your process to increase the likelihood of having a good estimate of the part-to-part variation. For example, do not measure consecutive parts, parts from a single shift or a single production line, or parts from the reject pile.

Operator and Part factors must be crossed. Two factors are crossed when each level of one factor occurs in combination with each level of the other factor. For example, if the Operator and Part factors are crossed, every operator must evaluate every part. For details, go to Minitab Help: Data considerations for Crossed Gage R&R Study.

Nested gage R&R study

Use a nested gage R&R study to assess the variation in your measurement system when every operator cannot measure all parts.

For example, you have 3 operators and 15 parts. Operator A measures parts 1-5 twice, Operator B measures parts 6-10 twice, and Operator C measures parts 11-15 twice. Each part is unique to each operator; therefore, no operators measure the same part. To see an example, go to Minitab Help: Example of Nested Gage R&R Study.

Data considerations

Part is nested in Operator. 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). For details, go to Minitab Help: Data considerations for Nested Gage R&R Study.