How does WIV (Within Part Variation) affect Gage R&R?



Please tell me about the formulation of WIV(Within Part Variation)when the within part variation affect the calculation of G R&R
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Al Dyer

Could you further define "Within Part Variation"?

Gage R&R measures equipment variation (repeatability) and appraiser variation (reproducibility) and i don't see how part variation works into the equation.

Part to part, there will always be some measure of variation when performing Gage R&R.




Pardon me dear aldyr, my target of this question was the base of calculating WIV which is porpused in qs9000 MSA manual (1995


Pardon me dear aldyr, my target of this question was the base of calculating WIV which is purposed in qs9000 MSA manual (1995 edition) page 66 figure 17 .can you introduce to me a reference about the theory of this formula
Alita, let me take a stab at this.
On page 45 of the MSA it describes the steps for conducting a study. Step 1 is to "obtain a sample . . . From this point we follow the rest of the steps to conduct and record the results of the study.
On page 64 it atates "where there is significant with-in-part variation . . .

This tells me that in the first study you cannot be absolutly sure your results are correct. After all the sample is taken from a production run.
The second study is needed to take into consideration the variation of the sample itself.
This is all JMHO

PS: You may get more feedback if you register.


dear friends , I think that you didn't pay attantion my exact question .in fact I know that the WIV is about the within part variation , but my exact question is about the base of the formula of this term.pardon me but i think that you don't want to answer an appropriate reply to my question untill I register!!!!


Not so Alita - The people here have nothing to gain by you registering. They are all giving their time to discuss questions in this forum in hopes of sharing and exchanging some quality knowledge.
I think the problem is intrepetation of the question. We come from many different backgrounds and some of us from different countries. It is sometimes difficult to get our thoughts on the same page.
I too am a little confused, but will offer the following:

Page 34 of the MSA Reference Manual outlines the way to compute the part variation in Gage R&R. The formulas used on this page are the same ones I put into my Excel program and they work fine. Maybe this is also off the question you post, but I am keying on the word "formula" in hopes of helping you.

If this is still off subject, please try to be patient with us and try to express the question in another way.

Alita, Refer to the "Juran's Quality Control Handbook" starting on page 22.44 also check out references that are noted. At some point you should be able to resolve your question.

Rick Goodson


You request information on the basis of the formula for calculating the Within-Part variation on page 66 of the 2nd edition of the Measurement System Analysis (MSA) manual from the Automotive Industry Action Group (AIAG). Within-Part variation was contributed by the General Motors Corporate Statistical Review Committee. I do not know how to contact the committee directly, but you could start by contacting AIAG in Michigan. Try through their website or telephone them at 1 810 358 3570.

Dear Alita,

The base of calculating the Within- Part Variation is being explained in MSA Ref. Manual at page 89.
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