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1.5 sigma shift – is it plus/minus or overall?

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  • #32973

    jediblackbelt
    Participant

    A real quick question on a subject that is beaten to death.  Does the shift work as a +/- 1.5 sigma or is the overall spread for a +/-.75 sigma?
     

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    #88614

    Ron
    Member

    +/-  1.5 

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    #88619

    melvin
    Participant

    From our experience we understand that the 1.5 Sigma shift is one sided.  Hope this helps…

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    #88620

    rwatters
    Member

    Eg. If your short term capability equals 3.2, your longterm would then equal 1.7.
    Add the 1.5 if youre going from long term to short term

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    #88622

    mcleod
    Member

    Bob is correct. The addition or subtraction of 1.5 is a one-sided calculation.
    If you use minimum capability analysis to determine Z or sigma level, you would EITHER add or subtract 1.5 to this number (depending on whether you are converting to short-term or long-term).
    The most customary approach is to determine overall Z or sigma level by backing into it based upon total DPPM, then performing the addition or subtraction of 1.5 (again depending on whether you are converting to short-term or long-term).
    However, despite what Mikel H. says, this conversion is nonsense! There is NO theoretical basis for such a conversion, and only very LIMITED empirical reasons for doing so.
    Hope this helps.

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    #88625

    Mikel
    Member

    amen on the nonsense

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Viewing 6 posts - 1 through 6 (of 6 total)

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