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1. When and how will the device be calibrated?

Each operator must clearly understand and consistently apply the calibration procedure to the

measurement tool.

Ideally, the device should be calibrated before the study begins and not recalibrated until the

study has ended.

- If it is necessary to recalibrate after each measurement, then calibration variation and

repeatability are combined (compounded).

- If each operator must calibrate before beginning a trial, then calibration and reproducibility

variation are combined (compounded).

2. How many operators?Nop

If only one operator exists (e.g., automatic machine): Nop = 1 (it is not necessary to force Nop> 1).

In this case, R&R is just repeatability.

The minimum is: Nop = 2

If several exists, Nop

= 3 or 4 (it is not necessary to have more).

Should represent the skills of the operators that would utilize the measurement system.

3. How many samples? Nparts

If possible: Nparts= 10

General rule: Nparts*Nop> 15. If not possible, increase the number of trials.

Reference MaterialPlanning A Gage R&R Study 1

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Reference MaterialPlanning A Gage R&R Study 2

4. How should the samples be selected?

The sample should be representative of the actual family of parts.

If from this same family there are 2 or more distinct groups, it is best to form 2 or more groups of

samples for the Gage R&R study, with specific ranges of values.

5. How many trials should be run? Ntrials

A trial is one measurement on all the samples by each operator.

In the cases as noted:

Ntrials= 2 where Nop*Nparts

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Reference MaterialPlanning A Gage R&R Study 3

7. Do I use individual measurements or averages?

If the measurement in production is a single measure, then perform the gage study with a single

measurement.

If the measurement in production is the average of several measurements, then perform the

gage study with the average of several measurements.

Make sure all operators report the measurements in the same manner.

8. How do I analyze the results?

Use Minitab tables and graphs to compare operators, parts and operator*part interaction

9. What do we do about one-sided specification limits?

Use the discrimination ratio and % contribution; or calculate the standard deviation (= s) andconsider the tolerance = 6*s. Realize that each case is often a unique case. But each case is

often a particular case, so use sound judgment.

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Reference MaterialPlanning A Gage R&R Study

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10. How can we tell if there is inadequate instrument measurement discrimination

(resolution)?

If the ranges calculated on the R&R form have three or fewer possible values < UCL, or

If more than 25% of the ranges = 0

11. What can be done about inadequate measurement discrimination?

Measure and report as many decimal places as possible. Limit calculations to one decimal

place more than the measured values.

Look for a better measuring device that can measure smaller units.

12. What is an acceptable gage?

The Gage R&R study is designed for a project, not for an auditor. Establishing internal

guidelines requires judgment on the degree of precision required for that instrument.