iSixSigma

DPMO

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  • #31568

    loire marteney
    Participant

    I need assistance understanding DPMO.  If I have 7200 deliveries per year and average 36 defects per year, with 8 opportunites per delivery for defect how would I calculate my DPMO?
    Thanks in advance,
    Loire

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    #83287

    Cone
    Participant

    It is (36 defects divided by (7200 deliveries time 8 opportunities per delivery)) all times one million, or
    (36/(7200*8))*1,000,000 = 625 DPMO or about 4.73 sigma
     

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    #83289

    Chip Hewette
    Participant

    One may interpret DPMO as defects divided by (events x opportunities) but this can understate the rate.
    If one is making a delivery and (a)the product puts a hole in the owner’s wall on the way down the hall and (b)is dropped by the delivery team at the living room, how many defects exist?  There may be eight opportunities for a defect to exist on one delivery, but in this case you have lost (damaged) the product as well as damaging the customer’s home.
    I suggest that you calculate the DPMO based on the boolean “OR” premise.  Any defect during a delivery means the delivery is defective! 36 defects divided by 7200 deliveries x 1 million would be the calculation if each defect occurred alone.  If you have multiple defects, the DPMO would diminish but not by the factor of the 8 opportunities per delivery.
    I suggest that if multiple defects exist these are great candidates for a chi-square analysis by product, delivery team, region, or whatever, in which you compare the count of “really bad” deliveries by appropriate subgroups.  From the available data you don’t have enough to do serious “A”nalysis, but maybe after you calculate the baseline DPMO you can collect or use more historical data and see if there are reasons for such occurrences.

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    #83292

    Cone
    Participant

    Chip,
    Are you making this up as you go?
    You have taken something straight forward and made it convoluted.

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    #83294

    Chip Hewette
    Participant

    Thank you for the kind words.
    No.
    It is not always simple.  I felt it best for the original questioner to think about the customer view of a delivery.  Although 36 / (7200 * 8) sounds like a great performance, in my view any defect is a complete failure of one delivery.  There is only one opportunity to satisfy the customer, when there are many opportunities to make a mistake.
    Perhaps my less-wordy response here will suffice to minimize the convolution.

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    #83297

    Cone
    Participant

    “I felt” has no place in Six Sigma.
    The question was about DPMO, not customer’s perception. If you do not agree with the concept of DPMO, say so, but don’t give the person poor guidance on the question they asked.
    Unless you think the original questioneer was an idiot, why would you assume they need a lesson in customer’s perception?
    DPMO = (defects/(units of work*opportunities per unit))*10^6
    Simple
    You are also welcome for the kind words, I am always impressed when people try to insert their own philosophies to something that is well defined.

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    #83310

    Tierradentro
    Participant

    Gary,
    Lighten up. Chip preaches to everyone. He has superior knowledge.
     
    John

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    #83315

    Texas MBB
    Member

    “Superior Knowledge”??
    While I agree with Chip’s assessment, although the whole defect vs. defective point can be argued until we are all blue in the face…
    …saying someone has superior knowledge to another is taking it a bit far.  From the few posts I have read from “John” I would say he needs to lighten up.

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    #83331

    Cindy
    Participant

    In our training – we teach the Black Belts to look at defectives – or to consider their projects from the customers point of view.  They are  not happy if you screw up 1 thing – even if you got the other 7 right! 
    We teach our managers to use DPMO – when they are comparing “apples & oranges” (unlike processes or products) and trying to decide where to assign resources.  But even then there are other considerations like cost, possible gains, possible consequences of doing nothing, etc.
    The final complication to DPMO – is how you define an opportunity……..

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    #83351

    Cone
    Participant

    how do you define an opportunity?
    I think its easy.

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