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1,5 sigma shift

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  • #46913

    OMER
    Participant

    I have read before that 6 sigma correspond to 3.4 ppm or i have found after that it’s not really 6 sigma but just 4.5 sigma.
    I need some clear explanation about what we call 1.5 sigma shift.
    Thanks in advance 
    Omer

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    #155757

    luke skywalker
    Participant

    Omer,
    Do yourself a favor and continue reading. Also, anticipate several ‘less than polite’ responses for asking this question, as the 1.5 sigma shift issue as been a common topic of discussion here for over 4 years.
    Given that, there is a veritable plethora of information about the 1.5 shift on this website – simply use the search tool and you’ll be directed to a number of articles and discussion threads.
    Outside of this forum, you might ‘google’ 1.5 sigma shift and Mikel Harry – that should get you a great reading list.
    I hope this helps.
     
     

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    #155760

    OMER
    Participant

    Thanks Luke for the advice,
    Regards,
    Omer

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    #155765

    Rpaul
    Member

    First, its not really ‘ppm’. It’s DPMO.
    Second, 1.5 sigma shift is something gererally taken care of by acheiving Six Sigma. It does not mean that 6 Sigma becomes 4.5 sigma after the 1.5 sigma shift. The Mean shift concept is rather used in statistical process control as a part of six sigma initiatives.
    The 1.5 Sigma Shift concept relates to a process’ tendency to vary over a  period of time, due to certain factors inherent to the process. The 1.5 sigma shift is a scientific estimate of the normal organic shift in the mean of a process over a period of time. What we try to do with the 1.5 sigma shift is that we try to make our process variation so low that even with a mean shift of 1.5 sigma, we still operate to achieve a minimum Cp and Cpk. Unfortunately this thing is a little too complex to explain this way. So google up, search through this site and you should find a lot of things to help you. You can ask questions whenever you need though!!
    Cheers.
     

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    #155768

    OMER
    Participant

    Thanks Rpaul,
    Regards,
    Omer

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    #155769

    Craig
    Participant

    When we start adding  poorly defined things like opportunity counts, the meaning of the six sigma metric gets more fuzzy.
    DPMO and the 1.5 sigma shift both are bad ideas in my opinion. The 6-sigma notion means that we want the process mean to be at lease 6 standard deviations from the nearest spec limit. In this case, each observation in an opportunity and PPM / DPMO are the same.
    The problem here is that we try to force Bill Smith’s original concept to fit too many scenarios!
     

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    #155951

    Pichaimuthu
    Participant

    If i have an sigma of 1.1 and .5 and an 2 sigma ,what does each of these mean.

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    #155952

    Pichaimuthu
    Participant

    WHAT DOES 1.1 SIGMA ,.5 SIGMA AND 2SIGMA MEAN.

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    #155953

    clb1
    Participant

    SIGMA  In all caps is a command issued to an attack dog.
    So
    1.1 SIGMA would be a command to the dog to attack and bite with a force of 110%.
    Similarly
    .5 SIGMA  would be a command to attack with only 50% of the force normally employed
     and, of course
    2 SIGMA would command an attack twice the maximum.  A command of 2 SIGMA would, under most circumstances be very MEAN.

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    #155954

    Craig
    Participant

    If you believe in the 1.5 sigma shift theory, use the sigma calculator located in this web site. (Look up about 5 inches!)
    Plug in 1,000,000 opportunities and then do a trial and error approach until you arrive at the sigma levels you are asking about.
    If you don’t choose to apply the 1.5 sigma shift theory, then subtract 1.5 from the Sigma result shown. (i.e 1,000,000 opportunities and 3.4 defects = 6 sigma. If you dont buy into the shift theory, then you have a 4.5 sigma process).

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    #155955

    Craig
    Participant

    How does the dog know whethter to use the shift or not? Just think if your ordered a 2 sigma command and the dog acually carried out the attack with 3.5 sigma force? You could get sued.

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    #155966

    accrington
    Participant

    Which breed of dog? Additionally, you assume that the dog speaks English. What if the dog was a Pembroke Corgi, and spoke Welsh?

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