# Formula of X-bar R chart

Six Sigma – iSixSigma Forums Old Forums General Formula of X-bar R chart

Viewing 8 posts - 1 through 8 (of 8 total)
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• #40398

lin
Participant

does someone has a knowledge how do we get the general formulae we are using in calculating UCL & LCL
Thanks

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#125210

Ken Feldman
Participant

Show a little initiative and use the search capabilities of the Internet.  Maybe you would have found this site among thousands of others.
http://www.sytsma.com/tqmtools/xbar-r.html

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#125212

Whitehurst
Participant

UCL / LCL = X bar +- 3 sigma / Root N
where sigma is R / D2 so ( x bar + – 3 (R bar / D2) / root N))
= (x bar +- A2 Rbar)
Darth correct me if I have recollected it correctly !!!

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#125214

Akram
Participant
#125222

Ken Feldman
Participant

Joe, you know that I am never one for being picky BUT, it would be X double bar plus/minus Asub2 Rbar.

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#125404

AK
Participant

How did we calculate A2 (in case of X-baar) and D3 & D4 (in case of R-bar).
Regards

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#125412

Joe BB
Participant

You are asking a very easy question. Why don’t you google it?
You have been given two links that answer your question, show some effort try the links. People like you make me (unfortunately) sometimes wonder if all-knowing, almighty Stan is not sometimes right.
No he cannot be right, he is too obnoxious and arrogant and ignorant and dumb to be right.
Stan can you name one living soul besides you who knows anything about 6 sigma or statistics?
I am sure that you can’t.

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#125424

Ken Feldman
Participant

Ak, I apologize for Joe BB’s rude response.  I don’t know what has gotten into him.  Here is a link that will answer your question.  Read the response from Gabriel, an infrequent but very bright poster.
https://www.isixsigma.com/forum/showmessage.asp?messageID=35638

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