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Use of 1.5 sigma shift and 3.4 DPMO

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This topic contains 7 replies, has 4 voices, and was last updated by  Kim Niles 18 years, 6 months ago.

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  • #27124

    Cone
    Participant

    All of this discussion is interesting. Just a few qustions for all of you who claim insight into what Motorola was thinking —

    How many of you have a clear and rational way of counting opportunities (by the way – it is opportunities to do things right, not how many ways it can go wrong or how many things you test or inspect)? If you do, please share your method with everyone.

    How many of you have a clear and rational way of counting defects (by the way – a defect is anytime you use more than the minimum resource required to do a task)? If you do, please share how this was implemented including data collection and how you count all of those automatic inspect and rework loops built into your process.

    I only know of a few places that do the above. And until you do the above, you are not really even in the game. All this philosophical energy can be better used doing the above for you enterprize.

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    #66007

    Ken Myers
    Participant

    Gary,

    I’m a little confused with your comment concerning opportunities. You mentioned “it is opportunities to do the right thing”. How do you determine this value for a product, process, service, or system you desire to improve? Any example(s) from your experience would be great.

    My training and understanding is that the word “opportunities” is derived from the Poisson Distribution where there are multiple “areas of opportunity” per unit. In this case a “unit” is consider a unit of work that you desire to improve. Within each area of opportunity out of many within a unit of work one or more defects could be produced.

    Much of the literature, including Motorola’s, is a little vague on how to determine the number of opportunities for a unit of work. But, Motorola has used the number of steps in a process in conjunction with the word opportunities. In modeling Rolled-Throughput Yield(RTY) for a manufacturing process as the number of steps increases, the RTY decreases given the yield per step remains the same. My understanding is that as the number of opportunities for a system increases so does its complexity. So, using this understanding one could consider a process step an opportunity. As the number of process steps increases so does the process complexity. This follows well with the use of RTY in characterizing a multiple step manufacturing or service process. The operable language I’ve worked with for years, and have read by others is “defect opportunities”.

    Do you have any cited reference for your definition of opportunities?

    Regards,

    Ken

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    #66012

    Tierradentro
    Participant

    The reason there is a 1.5 sigma shift is because, no one would buy a product called four and a half sigma. It’s all marketing.

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    #66015

    Kim Niles
    Participant

    Dear Gary:

    Thanks for your post. I love your definitions as I’ve been pulling out my hair lately trying to come up with similar ones.

    Our company is just moving to Six Sigma and we are wrestling with these topics. We’ve been asking “to what depth do we go to find an opportunity?” and “with millions of possible defect types, what do we call a defect for defect tracking?”.

    Your definitions help a lot but I’m still fuzzy with their correlation to CTQ’s (critical to Quality characteristics). Any ideas?

    KN: http://www.znet.com/~sdsampe/kimn.htm

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    #66035

    Cone
    Participant

    It is always delightful to see we continue to guarantee that people understand before they can call themselves Black Belts.

    You know what they say about opinions?

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    #66036

    Cone
    Participant

    Kim,

    Look at my response to Ken. If you want more, email me.

    Gary

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    #66038

    Cone
    Participant

    Ken,

    Good, thoughtful response. We need more like these. I will answer some of your wuestion here and give you a more complete answer by email.

    You wrote:

    Gary,

    1) I’m a little confused with your comment concerning opportunities. You mentioned “it is opportunities to do the right thing”. How do you determine this value for a product, process, service, or system you desire to improve? Any example(s) from your experience would be great.

    The first thing to note is that Six Sigma is a piece of a bigger system, not the system itself. The system has to include the thoughts of Lean and TQ as a minimum if you even want to be in the game. Lean is reducing or eliminating non value added activities, so any definition of opportunity that is focused on looking for defects would prompt us to do things contrary to the ideas of Lean; i.e. our management says our sigma level is too low, if opportunities are what we test and inspect for, we can improve sigma by increasing test and inspection activities. This is also contrary to the claim that improving sigma levels decreases cost. So the focus has to be on value added activities which always are where the item being worked on is different after than before in a way that is meaningful to the customer. So the basis for counting opportunities will always be a detailed process map of the process to be quantified (this should be part of your overall quality system anyway – a common language for knowledge transfer throughout the organization). Give me a process map you want quantified and I’ll walk you through it. Counting opportunities is easy and straight forward and can be done in an hour on even the most complex of processes.

    2) My training and understanding is that the word “opportunities” is derived from the Poisson Distribution where there are multiple “areas of opportunity” per unit. In this case a “unit” is consider a unit of work that you desire to improve. Within each area of opportunity out of many within a unit of work one or more defects could be produced.

    Agree, 100% — just understand that every area of opportunity can produce multiple defects, that does not make it multiple opportunities. The way the process must go, with the minimum resources, is the opportunity.

    3) Much of the literature, including Motorola’s, is a little vague on how to determine the number of opportunities for a unit of work. But, Motorola has used the number of steps in a process in conjunction with the word opport

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    #66043

    Kim Niles
    Participant

    Dear Gary:

    Regarding your previous post “3) Much of the literature, including Motorola’s, is a little vague on how to determine the number of opportunities for a unit of work. But, Motorola has used the number of steps in a process in conjunction with the word opport”, I think you were cut off…..Please continue!!

    Thanks.
    KN

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