Sunday, January 20, 2008


From the beginning, project managers are taught about the triple constraints:
1. Time also known as Schedule
2. Cost also known as Budget
3. Scope also known as Performance

Time and cost are self-explanatory. When it comes to the third constraint, different terms are used: scope (the most common one), performance, and, sometimes, quality.

Scope is a description of the project’s objective in terms of the objective’s requirements. If the project’s objective is to create a water-powered car, then the scope includes everything necessary to develop that car. Developing a new engine that runs on water is part of the scope. So are the selection of the car’s body and the final assembly of the engine into the car body.

While the scope enumerates all of the objective’s requirements, it also requires the performance of these requirements. The project team must perform the development of a new engine. The project team must perform the selection of the car’s body. The project team must also perform the final assembly of the engine in the car body.

Would you agree, therefore, that the two, for all intent and purpose, are synonymous? In fact, it may be more accurate to refer to the third constraint as Performance. While scope enumerates the requirements, it is silent about the performance of these requirements. Performance, when identified as the third constraint automatically implies scope and, more importantly, the performance of those requirements.

Then there’s the third term that’s sometimes used to refer to the third constraint—quality. Quality is incorrect.

Neither Scope nor Performance is synonymous with Quality. Performance is what the project has to do. Quality is what the customer wants.

Every project’s goal is a satisfied customer, i.e., a customer that is satisfied because the project's objective was met. Does quality figure in the outcome? It sure does but the measure of quality depends upon circumstances.

Sure, we know that a best practice of project management when gathering the project's requirements is to ensure that fuzzy terms like "quality" are converted into measurable and objective metrics.

The following discussion does not contradict that. I am merely making the case that Quality is not the proper term to use as the third constraint.

PMBOK, itself, specifically identifies the triple constraints as scope, time, and cost (Section 1.3). Then it continues... "Project quality is affected by balancing these three factors. High quality projects deliver the required project, service or result within scope, on time, and within budget."

There is no ambiguity there. Quality is not one of the limiting three. Quality is a goal and not a constraint. Quality can be more closely related to the schedule or the budget, depending upon circumstances. Consider these two examples.

First: quality might be a function of time. Let’s say that you expect your wife to give birth within a two-week window from June 15 to June 30. You have to finish the baby room on or before June 14. You make it but the shelves haven’t been installed and the crib is only partially assembled. Wouldn’t achieving one hundred percent quality mean that shelves were installed and the crib was fully assembled? On the other hand, the project (of preparing the baby room) can be considered successful since it met the project’s objective satisfactorily.

Second: quality might be a function of the budget. Your project consists of replacing the worn kitchen countertops. Both of you decided to replace everything with granite countertops. Unfortunately, the week before your purchase date, the price of granite countertops doubled. That made it exceed your budget so you decided to settle on Corian—another material that cost as much as granite before its price doubled. Quality, in this case, is more closely related to cost. The kitchen countertop project was successful despite the fact that you had to settle for a less-expensive material.

Don't you think these makes sense? I welcome any comments.

Until then, I urge you to keep this in mind. The third constraint can accurately be identified as the Scope or Performance. But it should never be Quality.

To the left is a graphic that incorporates this fallacy. Out of professional courtesy I shall not disclose its source website.

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