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What Are the Most Important Issues When Performing DOEs?

Six Sigma – iSixSigma Forums General Forums Tools & Templates What Are the Most Important Issues When Performing DOEs?

This topic contains 6 replies, has 4 voices, and was last updated by  Chris Seider 5 months ago.

Viewing 7 posts - 1 through 7 (of 7 total)
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  • #238505

    STEF
    Participant

    Hello, everybody, I have a very difficult time to answer this question any suggestion? Discuss the most important issues facing you in rigorous experimental design at lower and higher orders.

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    #238508

    Robert Butler
    Participant

    You will have to provide a little more detail before anyone can offer much.
    1. What is a rigorous experimental design?
    2. What are lower and higher orders?

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    #238518

    STEF
    Participant

    Hello, lower orders are the experiments with two or fewer factors and higher orders are the experiments with more than 2 factors.

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    #238524

    Robert Butler
    Participant

    Ok, that answers one of my questions. I still need to know what constitutes a rigorous design. Given your answer to the question of order I’m guessing all rigorous means is that you actually take the time to implement the design and not stop at some point and shift over to a WGP analysis (wonder-guess-putter), however, I would still like to know what you actually mean by “rigorous”.

    To your first question concerning two-three level factorial designs or any of the family of composite designs, the biggest issues for running a design are the issues that drove you to wanting to run a design in the first place – time, money, effort. What this typically means is taking the time to define the number of experiments you can afford to run and then constructing a design that will meet your constraints.

    From a political standpoint the biggest issue with running an experimental design is convincing the powers that be that this is indeed the best approach to assessing a problem. You need to remember that simple one-variable-at-a-time experimentation is what they were taught in college, it is what got them to the positions they occupy today and, of course, it does work.

    If you are in a production environment where you will be running the experiments in real time you will have to spend a lot of time not only explaining what you want to do but you will also have to work with the people involved in the production process to come up with ways of running your experiments with minimal disruption to the day-to-day operation. The political aspects of design augmentation can be difficult but, as someone who has run literally hundreds of designs in the industrial setting, I can assure you that the issues can be resolved to everyone’s satisfaction.

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    #238525

    Chris Seider
    Participant

    This random question needs some randomization in its answer.

    Selection of levels, factors, and don’t use your whole resources in one experiment are things to consider.

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    #238527

    Mike Carnell
    Participant

    @stef There is no way I would second guess @rbutler on statistics particularly DOE. Anything you get from him will be better than advice you will get almost anywhere. @cseider is good too but he kind of held back some although his advice to not spend all of your money on one experiment is dead on particularly if you are running a fractional factorial.

    My 2 cents worth. If you are running more than 5 factors you need to have someone who is really good look at your design. That is a lot of runs and managing 32 runs or more is difficult.

    Watch the amount of time you are going to spend. If it is going to take a couple days to build then you need to have a way to measure the day to day variation. Even if you think it will not make a difference someone will ask and you need to be prepared to address it.

    The smoothest DOE I ever saw run was one where the team did a FMEA on the DOE. They were proactively looking for issues in a systemic way. You do not want to get in the middle of this and have everything go south on you. It is expensive.

    Control is huge. You are going to manipulate some factors and make assumptions about those factors with the understanding everything else was controlled i.e. environment, raw material, tool wear, people, etc. Have a plan to control everything. There is a thing called selective attention. It can wreck a DOE in a heartbeat. This video may help. https://www.youtube.com/watch?v=vJG698U2Mvo

    Good luck

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    #238541

    Chris Seider
    Participant

    Great posting @mike-carnell

    Yea, I didn’t give my treatise on DOE design. :)

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