iSixSigma

K of Cpk

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  • #32771

    Kidy Chou
    Participant

    To whom may concern/ help,
    Can you advice me a explanation or definition about K of Cpk?Thank you a lot.
    Best regards,Kidy Chou

    0
    #87906

    David Oakley
    Participant

    Kidy
    My instructor said that it was “corrected” and that the reason that it was k instead of c was because engineers couldn’t spell. I don’t remember having ever heard any other explanation.
     
    David

    0
    #87908

    Loehr
    Member

    Hi Kidy,
    The “k” reportedly stands for the Japanese word “katayori,” which means difference or deviation. There is a relationship between Cpk and Cp, as follows:
    Cpk = Cp (1 – k)
    where k = ( | M – mu | ) / [( USL – LSL) / 2]
    M is the middle of the tolerance and mu is the process average
    As you can see from the above, k is a measure of how far mu deviates from the middle of the tolerance, which is often the target for the process average.
    k (which is only a function of mu) indicates the accuracy of the process aim, whereas Cp (which is only a function of the standard deviation) indicates the process precision.
    I hope this helps.

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