Lean and Six Sigma


August 11, 2017
By Darren Dolcemascolo

The Lean versus Six Sigma debate continues, primarily between consultants in both communities.  Why is this? Is it legitimate or useful to pit Six Sigma against Lean?  Let's talk about both of these methodologies.  Lean is a system based on continuous improvement and respect for people.  It focuses on providing the customer with a defect free product or service when it is needed and in the quantity that is needed.  In order to accomplish this, there is an emphasis on full employee involvement in the process of continuous improvement toward these ideals.  The system involves a problem solving process most Lean folks today call A3 Problem Solving by which teams work toward improvement of key metrics with coaching from their immediate supervisor.  The metrics and goals are based on company strategy, developed through a process called hoshin kanri or strategy deployment.  There are many lean tools and methods that can be used, depending on the type of problem or situation.

 Six Sigma is a methodology by which teams utilize DMAIC (Define Measure Analyze Improve and Control) to improve processes, primarily the reducion of variation.  It emphasizes a hiararchical structure of "belts" including Master Black Belt (expert level), Black Belt, Green Belt, and Yellow Belt (basic knowledge).   Green Belt level and above can lead projects of varying scope.   This generally requires a formal system for training and certifying "Belts."  Unlike Lean, Six Sigma does not emphasize all employee involvement in improvement and it does not have a daily continuous improvement methodology within it.  It is project based.

 The debate between practiitoners of both of these methodologies is amusing at least and probably worth reading once every several months or so for a little insight and a lot of good laughs, but the reality is that both systems can coexist.  We often work with clients that want to utilize both methodologies.  How might they coexist within an organization?  We generally recommend that our clients engage in strategy deployment to identify key goals, metrics, and initiatives that will allow for allignment of all levels of the organization.  This can lead to many types of improvement initiatives including kaizen or problem solving activities.   We utilize the A3 approach to kaizen, including daily kaizen and kaizen events.  However, some of the improvement initiatives or problems identified lend themselves to a Six Sigma DMAIC approach.  These would include complex problems that might benefit from rigorous statistical analysis and Design of Experiments.  While the DMAIC approach is not the only approach to such problems, it is a proven approach and a natural fit. 

Whether you are a lean purist or a six sigma purist, I would encourage you to think a little bit differently.  There is more than one way to approach a problem, and I would recommend that you allow for multiple approaches in some cases rather than creating a lean versus six sigma mindset, which really isn't on the minds of most decision makers with whom you might be dealing.   My experience is that this is more of an "lean community" versus "six sigma community" debate among consultants (either external or internal).  Most of your customers might be open to either approach.  It is up to you to help them understand both approaches and how to effectively utilize them.

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