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Tolerance zone for Gage RR.

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  • March 12, 2008 at 1:04 am #49565

    jediblackbelt
    ★ 20 Years ★
    Participant

    I need help on a subject for “can’t tell zone” on my spec limits.  I have a note written in my manual from a few years ago that from the gage RR you can develop a band around a spec limit where within it you can’t tell good from bad.  My note says it is 2/3 x the standard deviation of the measurement system.  Does this sound familiar to anybody?  If so, could somebody elaborate if that is correct or how do you calculate it?
    Thanks in advance.

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    March 12, 2008 at 11:44 am #169584

    Mikel
    ★ 10 Years ★
    Member

    I have never heard of the rule, but there is some logic to it.2/3’s is leaves about 25% of the measurement error hanging out there
    to hurt you. If you can talk your customer into doing the same on the
    opposite side of the spec, you’ve reduced your odds of him calling
    something bad that you’ve called good to almost zero.

    0
    March 12, 2008 at 11:44 am #169585

    Mikel
    ★ 10 Years ★
    Member

    I have never heard of the rule, but there is some logic to it.2/3’s is leaves about 25% of the measurement error hanging out there
    to hurt you. If you can talk your customer into doing the same on the
    opposite side of the spec, you’ve reduced your odds of him calling
    something bad that you’ve called good to almost zero.

    0
    March 17, 2008 at 12:14 pm #169767

    RonJ
    ★ 20 Years ★
    Member

    Hello, I think you’re talking about Probable Error. PE = 0.675 times your estimate of standard deviation. Dr. Wheeler wrote an article explaining this topic, “Relative Probable Error”.
    http://www.spcpress.com/pdf/Relative_Probable_Error.pdf
    Hope this helps.

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