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Formula of X-bar R chart

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

This topic contains 7 replies, has 6 voices, and was last updated by  Darth 13 years, 11 months ago.

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

    Darth
    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

    Darth
    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

    Darth
    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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