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H,M,L (9,3,1) QFD weighting question

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This topic contains 9 replies, has 8 voices, and was last updated by  John J. McDonough 15 years, 7 months ago.

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  • February 26, 2003 at 8:53 pm #31587

    lin
    Participant

    Can someone quickly give me a heads up on the logic of the weighting used in the QFD.  Why is 9,3,1 used for High, Medium, Low respectively instead of…say…3, 2, 1 or something else?
    Thanks in advance.

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    February 26, 2003 at 10:31 pm #83363

    Charles H
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    They are done this way so that the high priority items drive the weighting and makes it easier to differentiate the low and medium from high priority CTQs.
     
    Charles H.

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    February 27, 2003 at 3:29 pm #83389

    lin
    Participant

    I understand why there are different wieghts, but why specifically 9,3,1 rather than 3,2,1 or 6,3,1? 
    Any significance for using 9,3,1 rather than a different combination?

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    February 27, 2003 at 3:40 pm #83390

    Never Mind
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    It seems as if the guy who invented this liked each level to be 3 times more important than the previos level. However, if you think that other weighting is more appropiate for your case, I doubt that anybody will question that. Like with the FMEA, I don’t think there is a scientific basis behind the numbers.

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    March 1, 2003 at 12:59 am #83446

    Charles H
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    Let me try it this way. 
    Say you use the 1 (low), 2 (moderate), 3 (high) relationship weighting scale.  One CTQ on the QFD matrix has 12 low relationships identified, so it gets a score of 12 (12 x 1 = 12).  Another CTQ has two high and one moderate relationship, getting a score of 8 (2 x 3 + 2 = 8).  In this case, one would more likely pay attention to the CTQ with a score of 12 and may neglect the lower scoring CTQ, though it may be of much greater importance to the customer, overall. 
    Using the 1, 3, 9 system, the scores would be 12 (12 x 1 = 12) and 21 (2 x 9 + 3 = 21), respectively, thus giving the CTQ that is of a higher importance to the customer a more appropriate weighting in the QFD matrix.  Like I said, it helps to more dramatically differentiate the highs from the lows.

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    March 3, 2003 at 1:42 pm #83477

    John Noguera
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    Hi Chuck!
     
    Good answer.  I will use your example from here on!
    By the way I did some interesting simulation studies on the difference between multiplicative (ie FMEA) vs additive.  The rank results match closely at the high and low end but vary widely in the middle. 
     

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    March 3, 2003 at 5:57 pm #83494

    Charles H.
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    >By the way I did some interesting simulation studies on the difference between multiplicative (ie FMEA) vs additive.  The rank results match closely at the high and low end but vary widely in the middle. <
    Hi John – how goes it?  I’d like to see the study you did, when you get a chance.  You can send it to my email, or post it here if you think it would be of general interest.
    Take care, amigo
    Charles H.

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    April 9, 2004 at 3:58 pm #98312

    Edmund Sarpong
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    For the QFD Problem 1 Matrix, compute the
    a) Customer requirements absolute weight.
    b) Technical requirements absolute weight and factor
    c) Technical requirements relative weight and factor
    d) Which design and technical factors should be emphasized? Why?

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    April 9, 2004 at 7:03 pm #98313

    Isabel
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    Participant

    Can someone recommend which software to use for QFD, that is not very expensive, user friendly, and that could be downloaded for a trial period?
    Thanks

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    April 12, 2004 at 5:34 pm #98371

    John J. McDonough
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    Isabel
    QFD matrices are often quite large and not easily seen on one screen.  QFD sessions are generally held in a large group.  As a result, a good old large sheet of paper is often better than the software.
    For years I have done QFD with Excel (nasty), though recently I’ve run across two programs.  One was amazingly clumsy to use and the other breathtakingly expensive.
    This has prompted me to write something, but it still needs quite a bit of polish before it is ready for prime time.  My intent is for this to be free software.  I have used it on one project and it was pretty helpful compared to struggling with Excel.
    If you would like to try it out, send me your email address.  Keep in mind, though, that it really isn’t ready for prime time.  Still, it’s fast and relatively easy to use.  And, the price is right.
    I’m being a little selfish here – I wouldn’t mind someone else’s coments!
    –McD
    mcd@is-sixsigma.com
     

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