iSixSigma

SPC Sigmas

This topic contains 4 replies, has 2 voices, and was last updated by  John Wick 1 year ago.

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  • #55931

    John Wick
    Participant

    So im reviewing the SPC rules (Nelson rules) and Im trying to figure it out how can i calculate the sigmas (1,2,3) can someone help ? Can you share the formula please.

    Please see attached document so you can understand what im talking about

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    #202212

    Chris Seider
    Participant

    Have you searched this site or used google? Lots of calculations out there for limits and as long as you can divide by 3….should answer your question.

    https://www.moresteam.com/toolbox/statistical-process-control-spc.cfm

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    #202214

    John Wick
    Participant

    I know how to calculate the UCL and LCL,

    so if im getting this correctly

    lets say i have an
    X (average); 7.967
    USL;9.3518
    LSL ; 6.5822

    so…

    USL – Xbar 3 ? thats how i get every sigma?
    9.3518-7.976 = 1.3848
    then divided by 3 is = 0.4616

    then 1σ is = 8.4286
    2σ = 8.8902
    3σ = 9.3518

    Am i right?

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    #202215

    Chris Seider
    Participant

    You mean UCL and LCL? if so….yes but follow the formulas to calculate the limits.

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    #202216

    John Wick
    Participant

    yeah sorry UCL and LCL
    Correct! , yeah the UCL and LCL were calculated with formulas.

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