Understanding Gage RR

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• #41560

RonJ
Member

If a gage study gives 10% Total Gage R&R, can it be said that when using that measurement system to estimate standard deviation, 10% of the estimate is due to the measurement system?
I suspect things aren’t that simple. Thanks for any help.

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#130761

sumpat
Member

yes you are right

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#130784

Anuragi Raman
Participant

It is not standard deviation but variace (square of standard deviation).
In the example given, the interpretation will be: 10% of the observed variation is contributed by the measurement system. Minitab should give 10% contribution (of VarComp).

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#130791

AB
Participant

Standard deviation would be calculated and not estimated using a measurement system.

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#130819

Hola
Participant

If I understand your question right, then the anser is – NO!
If you use the measurement system to measure a bunch of parts to get the standarddeviation for the process, then the contribution from the measurement system is much smaller! First when the Gage R&R gets up in the area of >25% you can say that it has a significant effect on the standard deviation.
It’s late now. I will get back to you tomorrow.

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#130857

RonJ
Member

Thanks Hola,
Yes, I’m measuring a bunch of part to estimate the stddev of the process. If the stddev is 10 and the gage R&R is 10% then 0.1 of the stddev is due to the measurement system?

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#130859

RonJ
Member

Sorry, it should read: “If the stddev is 10 and the gage R&R is 10% then 1.0 of the stddev is due to the measurement system?”

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#130928

Hola
Participant

If gage R&R is 10%, and your standard deviation from the process is 10, then the standard deviation from the gage is approx 3,16.
Use the formula for adding standard deviations:
Observed standarddeviation * observed standard deviation = (R&R standard deviation * R&R standard deviation) + (real process standard deviation * real process standard deviation)
3,16*3,16 + 9,48 * 9,48 = 10*10
Best regards,Hola

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#130936

RonJ
Member

Great, that is exactly what I’m looking for.
Thanks again

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