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Six Constraints: An Enhanced Model for Project Control – Quality (#4 in the series Six Constraints: An Enhanced Model for Project Control)
By Jay Siegelaub – MBA, PMP, PRINCE2

PRINCE2™ employs “tolerances” – its term for these six constraints – as key project controls. They are dimensions of the project for which ranges of acceptability are defined, which are monitored to identify or anticipate when a plan has entered “problematic” or “exception” territory. They are needed and used at all three planning levels of a project – the project as a whole, any one stage or phase of the project, and at the detail work package level.

The Six Constraints are:

  • Time
  • Cost
  • Scope
  • Quality
  • Benefits
  • Risk

This article discusses Scope.

The quality constraint (or “quality tolerance”) is actually quite similar to that of scope – except that quality focuses on characteristics of a deliverable. When we address quality we are not looking to add (or delete) a new item. We are only looking to alter or provide flexibility (or “breathing space”) for some feature of an already-defined item – or to assure that a particular characteristic is present and working properly (quality checking). Here’s an example. If I am building you a custom-made table, and you say “I want the table only to be made from cherry wood,” then you have given me NO quality tolerance on that particular characteristic of the table. If, for some reason, I can’t find cherry wood, then I do not have the flexibility to substitute anything else, unless I ask your permission. With “quality tolerance” you might say “I want the table made out of cherry, but if you can’t find cherry, or it is very expensive (above a certain cost), then I give you permission, in advance, to substitute walnut or oak.” You have just provided me with quality tolerance. You are not adding a new item, just giving me flexibility on one of the item’s characteristics. If I can’t find good cherry wood, I can use oak without getting your permission.

Quality tolerance also operates in the realm of exactitude, which is a traditional measure for quality criteria. It represents the degree to which a developed item matches its defined characteristics. For example, if I ask for a table to be exactly 1 meter long, then if it is delivered at 99 cm or 101 cm it would be rejected. As an alternative I might have quality tolerance of +/- 1 cm. That means I could deliver a product measuring 99.5 cm or 100.8 cm, and it would still be acceptable, passing its quality criteria.

Quality works in the same mode as the other constraints. For example, if a project is running late or over budget, the project manager may still be able to deliver the expected items – but they might not be tested as thoroughly (ie, we do not assure that the characteristics are present and working properly – very common!), or some characteristics of that item may be reduced or eliminated. This is how quality operates as a constraint. Some models of the triple constraint triangle use quality instead of scope as the 3rd leg of the triangle. In many classic situations, when time or cost was strained, it was quality – usually through less testing or verification, but sometimes through dropped characteristics – that was compromised.

Jay Siegelaub has over 30 years of professional experience delivering and supporting projects in information technology, insurance systems, banking, and nonprofit strategic planning, as well as in the pharmaceutical, financial service, consulting, and consumer products industries. As a recognized educator he has trained thousands of project managers over the past 23 years, including 13 years as the Project Management tutorial instructor for the Drug Information Association.

Jay’s recent responsibilities included leading the North American Change Management and Training practices for a UK-based management consulting firm, training corporate consulting professionals in project and program management, and supporting clients in managing the “people” issues of their business change initiatives. He has authored articles on training, project management and information technology for various publications, and often presents at conferences, including the PMI North American Congress (1999, and 2004 – 2007), ProjectWorld and ProjectSummit.

In addition to his PMP® certification, Jay has his MBA in Organization Management from New York University’s Stern School of Business, and is an accredited PRINCE2™ Practitioner, Instructor and Examiner. He has taught and consulted in PRINCE2™ in North America for 10 years (the first US-accredited PRINCE2™ instructor), and worked for the company (and with the authors) that wrote the PRINCE2™ Manual for the UK government.

He has provided Change Management and Project Management consulting and training (including PRINCE2) to companies such as Sun Microsystems, NATO, the United Nations Development Programme, Bechtel, IBM, Philip Morris, Credit Suisse, JPMorganChase and Diageo.

Jay also consults in Organizational and Professional Development.

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