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The O from DPMO – how to establish opportunities

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  • #47858

    boettler
    Member

    Defects per million opportunities (DPMO) is the average number of defects per unit observed during an average production run divided by the number of opportunities to make a defect on the product under study during that run normalized to one million.My question is how / what do you classify as an “opportunity” in this context?Some defects can pass through a quality inspection and have little impact on the end product. Other defects can result in re-work or scrap.Moreover, overestimating the number of opportunities on a unit can artificially make the DPO of your product, process, or service look better that it really is by inflating its number of opportunities.Any guidance or help would be appreciated!Rob

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    #160102

    Erik L
    Participant

    Rob,
     
    You’ve hit on one of the biggest reasons that people took issue with six sigma as it was initially rolling out.  Opportunity counting is critical in ultimately calculating a DPMO and subsequent conversion into sigma level and there were times where all that people did was change their operational definition of opportunity and presto they had a higher quality level.  Of course, nothing had really been done to the process and the customer was still experiencing defects.
     
    There’s really no specific guidance that can be given on opportunity counting.  I can give you some techniques that I’ve used in the past across a few different industries.  Pick one and use it.  Consistency is truly key here.
     
    1.)    Make the opportunity count equal to 1.  The product either meets the need of the customer or it does not.  This is the most conservative of approaches.  Its pro?  It’s simple and probably the most reflective of what the true customer feels.  The con?  It doesn’t take complexity of the offering into account.
    2.)     If you’re looking at the quality of delivered product, take the BOM for the product and multiply by three (for total opportunity count).  This was a basic ROT that was used at one of the companies that I worked for that was in the aerospace industry.
    3.)    If you’re looking at a process.  Assess the number of independent steps in the process.  Or, if you’re interested in only one area, the number of independent actions that occur to transform the inputs to some intermediary output.
    4.)    With a team of SMEs, come to some consensus on the opportunity count.  Use that to establish your baseline, work your improvements and then reassess post improvement.
     
    Hopefully this has provided you with several options of how to proceed.
     
    Regards,
    Erik

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    #160104

    boettler
    Member

    Some great guidance – thanks for this!Rob

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    #160443

    Roger Noble
    Member

    Erik has some valid points… the key one is “consistency”. As he states, make sure everyone is in agreement of the approach you use. There are 2 methods to think of opportunities but never the 2 shall cross or your analysis will be flawed.
    If you want to know which approach to use when, think of it this way. Are you analzying cost/time efficiencies? If so, you need to factor in all the probable opportunities for delays or defects in the process as they would relate to a flawed product or a delay in delivery due to rework/scrap. If you are looking just at quality, then yes, I’d agree with the opportunity = 1 approach, either it meets the expectation or not. However, his is ok for a start, such as when you are designing a new product or process but usually it does not give value to the business strategy of reduced costs and increased throughputs.

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