Interest in Six Sigma is growing rapidly within the professional project management community, and the most common question coming from that group is something like “How does Six Sigma relate to the Project Management Body of Knowledge (PMBoK)?” Six Sigma and PMBoK do have connections, similarities and distinctions.

Before diving into specifics, a little background doesn’t hurt. The PMBoK is a well-established standard (promulgated by the Project Management Institute) that is widely used by professional project managers in many industries around the world, and is the basis for certification as a project management professional (PMP). The PMBoK consists of nine knowledge areas organized into five “process groups” as illustrated in Figure 2, lower in the article.

As specific connections are explored, it is useful to identify and comment on several different perspectives from which this topic can be considered.

What Is Meant by “a Project”?

This is not asked in the rhetorical or definitional sense. It is asked to point out an important distinction between a project that is being executed to develop a new product or process (or to enhance something existing) versus a Six Sigma project that may be concurrently executing in parallel with, and potentially intersecting with, the “product project.” The following diagram illustrates this distinction.

It is possible that several Six Sigma projects may be executing at the same time as a “product project” and may deliver results that impact or are used by that project. A DFSS (Design for Six Sigma) project could be chartered to better understand the requirements of a certain customer segment, with the intent to deliver that knowledge to the product project team at the appropriate time. Similarly, a process improvement DMAIC project might be initiated if it were recognized that testing capability was insufficient to deliver the required level of quality within the required time frame. Both Six Sigma projects could have results that impact other product project teams as well, and so are not merely tasks within the product project, but have a life of their own.

PMBoK as a Guide to Execution of Six Sigma Projects

At a conceptual level, many of the “management best practices” advocated by PMBoK and Six Sigma have a great deal in common (e.g., identify and communicate with stakeholders; have a sound plan; conduct regular reviews; and manage schedule, cost and resources).

In the Six Sigma project world, most practitioners would likely argue that these types of activities are the province of the project sponsor/Champion and the team leader, typically a Green Belt or Black Belt. It is generally accepted as best to keep Six Sigma projects time limited (typically four months or so) and to execute them with small teams. Thus, it can be argued that appropriate management controls for projects of this nature may be primarily in the nature of individual results goals for sponsors/Champions and Belts. Six Sigma practitioners may resist additional oversight from a project office or other manifestations of professional project management.

In contrast, an argument can be made that professional project management finds its best application in larger, more complex “product projects.” In these situations, more formal and resource-intensive oversight by a mechanism such as a project office is appropriate. With large projects, individual results goals may not provide adequate control to ensure desired outcomes and accountability. In the balance of this discussion, “professional project management” is used to denote a larger, more complex project. It is not intended to suggest it does not apply to smaller efforts, or that all of the generalizations associated with larger projects will apply in smaller efforts.

In short, where it is well established that professional project management adds value to larger projects, it is not clear that the same is true for typically smaller Six Sigma projects. When Six Sigma projects truly follow the Six Sigma roadmap and faithfully conduct tollgate reviews, the additional overhead associated with project office controls and reviews may not be justified.

Six Sigma as an Aid to Professional Project Management

Application of professional project management is not synonymous with application of Six Sigma. Both disciplines do share many common goals and intent. Both seek to reduce failures, prevent defects, control costs and schedules, and manage risk. Generally speaking, professional project management attempts to achieve these goals by encouraging sound practices on a project-by-project basis, often through the mechanism of a project office that promulgates policy, provides templates and advice, promotes appropriate use of tools such as critical path method, and perhaps performs periodic project reviews.

Six Sigma is more typically oriented toward solution of problems at root cause and prevention of their recurrence, as opposed to attempting to control potential causes of failure on a project-by-project basis. Six Sigma’s set of tools are more broadly applicable, than those commonly applied within the discipline of professional project management. Recognizing that project management is itself a process, Six Sigma is potentially applicable to its improvement.

Both sets of practices bring value and are best applied in conjunction with one another.

Six Sigma and PMBoK Process by Process

PMBoK Initiating Process – This PMBoK process group relates most directly to “Define” in Six Sigma. This first phase or process includes preparation of a project charter and assignment of a project manager.

PMBoK Planning Process – The Six Sigma thought process and toolset have many intersections with this process group. The PMBoK areas most closely related and the most prevalent Six Sigma connections to each may be summarized as follows:

• Project Plan Development, Scope Planning, Scope Definition – “Requirements failures” are one of the most common problems encountered in project planning. Six Sigma’s DFSS brings a rich toolset to address these issues, including Kano classification, needs/context distinction, KJ analysis, and other language processing tools that help to reveal latent and unstated requirements – sound planning begins with a clear understanding of the voice of the customer.
• Project Time and Cost Management – Six Sigma tools also help to prevent “expectations failures” caused by poor estimates and inadequate exploration of prioritization and feature selection issues. Six Sigma brings tools such as analytical hierarchy process, conjoint analysis and concept selection scorecards that promote fact-based conversations between the project team and the customer. Proper use of this set of Six Sigma tools will reduce the occurrence of political decisions about schedules and budgets that commit project teams to run the proverbial “three-minute mile.” (The world record stands at about 3:40.)
• Quality Management – Six Sigma’s emphasis on predicting and managing “capability” together with tools such as defect containment scorecards promotes understanding and managing the economic consequences of escaped defects. Six Sigma tools such as combinatorial methods and Markov chains can be applied to improvement of testing processes.
• Risk Management – Six Sigma tools such as Monte Carlo simulation (if not already being used) can find application within the context of professional project management.

PMBoK Execution Process – Six Sigma can complement product project execution primarily in the areas of risk management and in optimization through application of tools such as design of experiments, which can be used to find “what’s best” solutions.

PMBoK Controlling Process – Six Sigma complements Controlling in two primary ways. First, as it solves problems at root cause, it tends to prevent problems from reoccurring. Second, in the final step of the DMAIC improvement process (Control), controls and responses to special cause variation are institutionalized so that reaction to control issues is both rapid and sound.

Conclusion: Six Sigma a Complement

In the end, it is clear that Six Sigma complements and extends professional project management, but does not replace it. Both disciplines make important contributions to successful business outcomes.