Utilizing the Difficulty Metric

When I asked why they had removed the “difficulty” row from their QFD, I was met with questioning glances and the response, “difficulty row?”…I encouraged them to scrape off the glue and reinstate the difficulty column in their QFD. Doing so would not only allow them to communicate to stake holders why certain features were being temporarily skipped, it would also help them to more accurately remember estimates for features that became de-prioritized due to changes in upstream Houses of Quality….Before you decide that entering difficulty values in your QFD isn’t worth the effort required to do so, you should consider whether or not difficulty will affect your prioritization. If cost, complexity, and/or difficulty will affect your prioritization, then before you decide that entering difficulty values is too laborious, perhaps you should instead ask yourself, “how hard can it be?”

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I was recently reviewing a QFD that was created by a group of software developers. They had opted to omit several traditional columns, rows and/or matrices, and had added some new ones. On their final House of Quality they had added a “status” column. Many of the top requirements on this HOQ (the list was sorted by calculated importance) had status values of “Prioritized” or “Completed”. However, I noticed that several of the highest ranked requirements had been skipped and had no status at all. I assumed that these items had no status because they had only recently been added to the QFD. However, I soon learned that my assumption was wrong—these items had been skipped because there simply wasn’t enough time left before the upcoming version release to try to bite off such complex or difficult features.

I asked the team how they knew that a given feature was too complex or time-consuming to complete before a scheduled deadline. I was informed that team members were assigned to do some preliminary analysis on top features in order to estimate how difficult it would be to complete them. When I then asked where they logged this information, I was informed that they “just remembered it”. I then asked how they communicated this information upstream to the business stake holders and received some blank stares. When I asked why they had removed the “difficulty” row from their QFD, I was met with questioning glances and the response, “difficulty row?”

In their attempts to modify their QFD to suit their needs, this team had mistakenly removed a component that was of significant value to them. In remodeling terms, they had covered up their marble floors with carpet glue and a shag rug. I encouraged them to scrape off the glue and reinstate the difficulty column in their QFD. Doing so would not only allow them to communicate to stake holders why certain features were being temporarily skipped, it would also help them to more accurately remember estimates for features that became de-prioritized due to changes in upstream Houses of Quality.

What Does It Measure?

For those of you unfamiliar with the difficulty row on a House of Quality, it is used to rate a requirement in terms of its difficulty to accomplish. It is frequently labeled “technical difficulty” or “technology gap”. It can be used to measure any kind of challenge ranging from organizational difficulty to financial cost. Scales of zero to five, or zero to ten are generally used with zero indicating that something is extremely easy and a maximum value indicating that a stepwise improvement in technology, culture, or funding would be required in order to accomplish the requirement.

Some groups have modified the traditional scale for difficulty in order to make evaluation easier and less prone to debate. These teams have opted to use an exponential scale of one, three, and nine because of the psychological effect of dramatic changes in magnitude. One team that I know uses this scale and have agreed that a value of one indicates that the requirement will take days to accomplish, a value of three will take weeks to accomplish, and a value of nine indicates that the requirement will take months to accomplish.

How Accurate Is the Measurement?

Many people are concerned about the subjectivity of measuring “difficulty”. While their concerns may be somewhat valid, I would propose that a subjective rating is better than no rating at all. Even if the measure is somewhat prone to reproducibility or repeatability errors, there is bound to be some value in knowing that a requirement’s difficulty was scored as a “nine” vs. a “two”.

If you wish to improve the accuracy of this measurement, you can create an exhaustive legend of what each value means (not just the polar values). This legend will remove the ambiguity between a value of “1” and a value of “2”. If you wish to take it a step further, you can always perform a Measurement Systems Analysis (MSA) on your difficulty evaluations.

How Hard Can It Be?

Although I am a big proponent of remodeling the House of Quality to suit your needs, I am also careful not to throw the baby out with the bath water. Before you decide that entering difficulty values in your QFD isn’t worth the effort required to do so, you should consider whether or not difficulty will affect your prioritization. If cost, complexity, and/or difficulty will affect your prioritization, then before you decide that entering difficulty values is too laborious, perhaps you should instead ask yourself, “how hard can it be?”