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Z-Value (Sigma Capability)

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  • #39813

    Shad
    Member

    Could I get an entire derivation of Sigma capability viz., Z-value, Z-bench,etc. & how it affects process from any of the experts?

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    #122101

    A.S.
    Participant

    Are you asking about sigma level calculation?
    Sigma levl of any process can be calculated using a formula
    Sigma Level = 0.8406 + SQRT (29.37-2.221 X lnPPM)
    Hope that thisis the required by you.
     

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    #122103

    Shad
    Member

    Does it include Z-Lt ? Anbu.If yes, how can we derive this ?  

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    #122116

    Mikel
    Member

    All of this z talk is a bunch of crap. What you need is Cp, Ppk, and Cpm. Go read the Minitab help menus and come back with questions that show you have done that.
    In simple terms
    Sigma Level = zbench = 3*Cp
    zst = 3*Cpk (a meaningless number)
    zlt = 3*Ppk
    And Cpm? It is the one that tells you about the economic waste of your process. And what is the zxx value in Harry speak? There is none, he is not smart enough to understand.

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    #132233

    Prin
    Participant

    Can the sigma levl of any process be calculated using formula …0.8406 + SQRT (29.37-2.221 X lnPPM.. even if the process is not normal (e.g. weibull distibution)?

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    #132236

    Mr IAM
    Participant

    Stan – Thanks for your enlightenment.  Now I am sure everyone will dump sigma and go back to Cpk.  Because we all want to learn from someone smart enough to understand.

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