# Expected Values for EV, AV etc in a GRR Study

#### Howard Atkins

Staff member
Values for EV, AV

I cannot find or in the MSA book or here or there any explanation of the values required or interpretation of the values for EV, AV, PV and TV.
What numbers are we looking for .
Can any one help.

Best wishes for the season to you all

#### Marc

##### Hunkered Down for the Duration with a Mask on...
Staff member
EV Rings a Bell

EV rings a bell, but of course, at two letters and that those letters are what they are and their sequence, a search would be - well, interesting to say the least.... I know this search engine here won't even take 2 lone letters - 3 is the minimum.

What context? Where did you get the initials to begin with?

#### Howard Atkins

Staff member
Sorry if I was not clear but these are the terms in the MSA book for the calculation of Gauge R&R
EV=Equipment Variation
AV= Appraiser Variation.

#### Marc

##### Hunkered Down for the Duration with a Mask on...
Staff member
Ah! So PV = Part Variation and might TV = Test Variation?

I knew I had heard the initials but couldn't remember where from.

#### Howard Atkins

Staff member
TV= Total Variation
You pasted info about EV at my other post
Thats why you remembered.

Seriously does anyone know the answer.

#### Marc

##### Hunkered Down for the Duration with a Mask on...
Staff member
> explanation of the values required or interpretation of
> the values for EV, AV, PV and TV

Yes - I'm that stupid. OK - We're talking Gage R&R where EV + AV + PV = TV, right?

I'm sorry I don't have the equations at hand (I think that's what you're asking) - I don't do R&Rs regularly - well, it's been some years in fact. I used to use a spreadsheet with pre-defined formula - and I know you know there are a lot of examples of R&R spreadsheets here. You might want to look at the calculations in a spreadsheet or two.

Have you looked through MSA_Guide_M.ppt in http://Elsmar.com/Cove_Premium/MSA_Mains/ ? Most of the formula are in there. Or am I missing something in your question? (I do remember the Ideal Gas equation! pv=nrt )

Or... maybe one of the wizards who visit that really know R&R can give some detailed info.

#### Howard Atkins

Staff member
Ok maybe I have not been as explicit as I meant to be.
%R&R needs to be below 10% for the gauge to be usable.
The calculations I know and have speadsheets to do them , what I want to know is:
what values are expected for EV and AV and how does one evaluate the results?
This is not in the MSA book and I cannot find the answer on the net.
I hope that this is now clear.
Thanks Marc

A

#### Atul Khandekar

AV,EV,PV,TV....

As far as I know there are no 'expected' values for AV and EV. Only they should be as low as possible. You could look at the 'contribution' of each error or variation in the Toal Variation. The contribution of PV (part-to-part variation) should be maximum because that's what a measurement system is supposed to do : detect part-to-part variation.

Apparaiser Variation can be easily detected if you do graphical analysis using control charts. You can find out thing like whether a certain operator requires more training, whether you need better methods/fixuring etc. Typically each operator's Range chart would show you repeatability of that operator, X-Bar chart will show you the ability to detect part-to-oart variation. You could compare charts for different operators to know more about reproducibility. If you compare charts, any need for improvement will also become apparent.

Hope this helps.

-Atul.

#### Howard Atkins

Staff member
Thank you Atul ,

Can you give me some imput on these numbers or do you need more information
measured 24.80±0.08
EV = 0.012 % EV = 7.37
AV= 0.010 % AV = 6.27
PV= 0.040 % PV = 24.98
TV= 0.043
R&R= 0.015 % R&R =9.68
measured 0.8+0.3
EV= 0.10 %EV= 21.67
AV= 0.042343873 %AV= 9.58
R&R= 0.10 %R&R= 23.69
PV= 0.43 %PV= 97.15
TV= 0.44

Am I just looking for something that is not there?
Thanks

Staff member