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…moving into the House of Quality

It All Depends

December 22nd, 2008 by Peter Wolfe

PERT ChartI still remember the Brady Bunch episode in which Greg talked his parents into remodeling their attic into his bedroom (after a fight with Marcia over whose room it should be). From the moment I first saw that show, I dreamt of overhauling my parents’ attic. Today, many engineers are doing just that–-repurposing their attics and making better use of them. However, the attics which I am referring to are not in their homes, but rather in their Quality Function Deployment matrices (i.e. “Houses of Quality”). Although many customizations have been made to the QFD “roof”, my favorite modifications is the addition of the “dependency” concept.

Repurposing the Roof

For years, I questioned the return on investment provided by filling out the “roof” portion of a House of Quality. It is a very tedious process. I also frequently forgot to review the roof during actual product development periods. To be honest, I was never entirely certain what to do with the knowledge that two requirements had a positive or negative correlation. The fact that they had a positive correlation seemed simply to be a bonus that didn’t really require documenting. Additionally, negative correlations seemed like an unfortunate fact that simply had to be accepted as one tackled requirements in prioritized order.

The advent of new design principles have brought me renewed value for the data documented in the roof of an HOQ, however. For example, negative correlations can assist in identifying “contradictions” for use in the TRIZ methodology.

Remodeling the Roof

Yet, it is not just the repurposing of the roof that has made it valuable, but also the remodeling of it. One such redesign is the addition of the “dependency”. Many times requirements are not just correlated, they are dependent on one another. Under these circumstances, it is sometimes impossible to satisfy one requirement without first addressing another. This means that a requirement with a lower relative weight may need to be completed before a much higher ranked requirement.

Applications in Agile

Take software development, for example: a feature such as “user account creation” may have a substantially lower relative weight than “editing and retaining user preferences”. In reality, user accounts are of little value in and of themselves. It is only when additional features such as “data security”, “user-to-user communication”, and “user preference administration” are added that user accounts become of value. However, these valuable features cannot be added until after the ability to create a user has been added.

Under Agile development methodologies, the list of requirements in the “Feature Sets vs. Features” House of Quality can become quite large (measured in hundreds). In this setting, it is quite difficult to keep track of the various dependencies that may exist so that development assignments can be doled out in a logical fashion. By documenting dependencies in the correlation matrix of a QFD, however, a product manager or project leader can quickly determine if the feature with the highest relative weight is truly the next feature that has to be developed. If the feature with the highest weight depends on another feature, then it is the “depended-on” feature that must be addressed next. (Occasionally, a trail of dependent requirements must be followed until one is finally found that doesn’t have any prerequisite features.)

Innovations in Innovation

I truly am fascinated with the modifications that engineers and analysts have been made to the House of Quality matrix. The addition of concepts such as “dependencies” is evidence that just like products or services, methodologies need to be continually refined in order to ensure their usefulness. In short, remodeling in response to the voice of customer leads to greater value. (Perhaps if I could have convinced my parents of that principle, they would have let me turn our attic into my bedroom.)

This entry was posted on Monday, December 22nd, 2008 at 4:00 pm and is filed under House of Quality, Remodeling the HOQ™, Agile, Quality Function Deployment, QFD, TRIZ. You can follow any responses to this entry through the RSS 2.0 feed. You can also leave a response.

2 responses about “It All Depends”

  1. volkan said:

    the best internet page

  2. Joseph Schwendler said:

    The concept of dependency is a great insight. I will use this now going forward.

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