# Gage R&R sheets - What do EV & AV mean?

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#### Star18

Someone can help and gives some light about the GRR shhet?

EV - The Equipment Variation used for repetability. What does this coefficient mean?

AV - Appraiser Variation used for the reproductibility. Does Appraiser means men who (the operator) measure parts on the control mean because for calcultating it we need the number of operators? or the appraiser means the appartus itself? So the AV value will mean the Variation on the appraiser.

Thanks in advance.

#### Jim Wynne

Leader
Admin
Star18 said:
Someone can help and gives some light about the GRR shhet?

EV - The Equipment Variation used for repetability. What does this coefficient mean?

AV - Appraiser Variation used for the reproductibility. Does Appraiser means men who (the operator) measure parts on the control mean because for calcultating it we need the number of operators? or the appraiser means the appartus itself? So the AV value will mean the Variation on the appraiser.

Thanks in advance.

GR&R represents an attempt to predict A) the amount of variation contributed to a process as a result of measurement error, and B) the sources (different types) of measurement error. EV (equipment variation) is error attibuted to a device without regard for other factors (such as who is operating it)--the device may be expected to evince the same level of bias with all operators. AV, or appraiser variation, is the variation that emanates from the (usually human) operators of the gage, again independent of other factors.

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#### Star18

AV meaning.

Thanks for your answers.
But I'm still a little confused about the AV - Appraiser variation. I mean that in a french translation, The 'Appraiser Variation' translated in an official document (the provider of our company in term of QS9000 standards) with: 'Variation de l'estimation' and as you can understand, in english it means: 'Estimation Variation'.
Thanks in advance for your help.

#### Jim Wynne

Leader
Admin
Star18 said:
Thanks for your answers.
But I'm still a little confused about the AV - Appraiser variation. I mean that in a french translation, The 'Appraiser Variation' translated in an official document (the provider of our company in term of QS9000 standards) with: 'Variation de l'estimation' and as you can understand, in english it means: 'Estimation Variation'.
Thanks in advance for your help.

Theortically speaking, appraiser variation is intended to account for differences in operators' use of the device. For example, if operators A and B are using a device one way, and operator C is using it differently, such that the measurement results are affected, the result is appraiser variation. It's important to understand though, that it's not a democratic process. Just because results from two of three operators agree doesn't mean that they're "correct." The idea is to isolate operators as a source of variation. Once you've done that, you still have to investigate and determine (and verify) what's actually going on.

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#### Star18

Appraiser meaning.

Thanks Wynne for tips you brought me.
Just one more thing, I looked for translation in french of the word "Appraiser" but I failed. Does the meaning: "Operator"?
Thanks in advance.

#### Jim Wynne

Leader
Admin
Star18 said:
Thanks Wynne for tips you brought me.
You're welcome.

Star18 said:
Just one more thing, I looked for translation in french of the word "Appraiser" but I failed. Does the meaning: "Operator"?
Yes. In English the verb "to appraise" means to evaluate or judge the quality or value of something. The not-always-reliable Babelfish translator gives the French equivalent of "appraiser" as priseur.

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#### Star18

Appraiser meaning.

Thanks for your quick reply.
Yeah, in fact I found this word after translation (priseur) but in french this word means another thing.
Anyway, explanations you gave me are enough for me to understand the meaning.
Thanks.
Dida.

M

#### mustafa siddiqui

Guage R&R

Gauge R&R
I would go and talk to the manager manufacturing, and request 2/3 good appraisers and about 10 samples. Now ask each appraiser to measure the sample 2/3 times and note down the readings in the Gauge R&R chart. Once all the readings are noted, feed the same into the chart.
After calculations we get the results after feeding in the LSL and USL. Since the number of samples being taken are less than 7 the LCL will be zero.
The following are the formulae to be used while calculating the values to be judgmental

EV = r Rbar bar

EV= equipment variation
r = 4.56 for 2 trials, 3.05 for 3 trials
Rbar bar = range between max sampling value and min sampling value

AV = appraiser variation
K = constant = 3.65 for 2 appraisers, 2.7 for 3 appraisers
n = number of samples
r = 4.56 for 2 trials and 3.05 for 3 trials
Xdiff = max(x1,x2,x3) – min (x1,x2,x3)

Repeatability and Reproducibility

R&R = SQRT (EV2 + AV2)

PV = j * Rp

PV = part variation
J = constant dependent on the number of parts =
Rp = Range of part averages

Part 2 3 4 5 6 7 8 9 10
j 3.65 2.7 2.3 2.08 1.93 1.82 1.74 1.67 1.62

TV = SQRT (R&R2 + PV2)

TV = Total variation

Percentages of total variations can be calculated as following.
% EV = (EV/TV)*100
% AV = (AV/TV)*100
% R&R = (R&R/TV)*100
% PV = (PV/TV)*100

Result interpolation
If repeatability is greater than reproducibility (EV>AV), which means error of equipment is greater than the appraiser/ operator:
• Gauge instruments needs maintenance.
• Gauge need to be redesigned.
• Clamping locations need to be improved
• Excessive within - part variation.

If reproducibility is greater than repeatability, which means error of operator is greater than equipment:
• Operator needs to be better trained on how to use and read gauge.
• Calibrations on the gauge are not clear.
• Fixture required helping operator use gauge more consistently.

Gage system acceptability
% R&R < 10% gage system is OK (most of the variation is because of part)
% R&R < 30% may be acceptable depending on importance of application and cost
of gage or repair
% R&R > 30% Gage system needs improvement (people and gage responsible for
1/3 of the problems).

#### New to statistics

##### Involved In Discussions
Hello just a quick question
If you want to compare the above indicators with the minitab output you will check from gage Evaluation the Study Var right?
(note the output is not from the above data)

#### Miner

##### Forum Moderator
Leader
Admin
Focus on the results outlined in red. These are the basis for the numerator of all the metrics and are most likely to be calculated incorrectly by a spreadsheet. Then verify the Total %SV, Total %Tol and Total %Contribution to be safe. This is to verify that the denominators are correct.

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