Six Sigma

Six Sigma Control Phase is Not Anti-Lean

By Ron Pereira Updated on March 5th, 2008

Last night I posted a question and now realize I was a bit too vague.  This question was brought on due to a recent conversation I had with someone who asked me if I thought the “control” phase in the six sigma DMAIC roadmap was perhaps a bit too dictatorial, and even a tad anti-lean in nature.

This individual is lead to believe that the control phase means a Six Sigma practitioner works on a project, makes it better, and then people are required to “control” the gains or pay the consequence.  Now I am paraphrasing here but this is the gist of their argument.  So, I wanted to spend some time this evening responding.

Some Valid Points

Initially, when confronted with this question, I felt the need to defend six sigma.  I work very hard to promote how we need to leverage the strengths of both lean and six sigma and this argument initially seemed counter productive to me.  But after some thought I realized that this person did make some good points.  Here’s why.

  1. Too many times six sigma “belts” work hard in the D, M, A, and I phases.  They make things better and all seems well.  The issue is they don’t place enough emphasis on making the gains stick in the control phase and things sometimes resort to their old ways.  While this was not one of this persons main arguments I can’t help but think of it in this discussion.
  2. As Jon Miller alluded to last night there can be a tendency to “stop” improving a process once the green or black belt complete their project.  In fact, once the “hand off” is made to the process owner improvements of any kind may stop completely.  This ain’t good.

But Missing the Point

While this person did make some good points they are missing the point behind how the control phase in six sigma is supposed to work. 

You see, the power of six sigma comes from the simple formula: y=f(x).  Our output (y) is a function (f) of the inputs (x).  Once we identify the critical x’s and optimize them we must set in place plans to maintain the gains. 

These plans are not dictatorial or heavy handed like this person thinks.  Instead the plans are focused on controlling the process via tools like SPC, Poka-Yoke, and Control Plans.  For those of us that dabble in lean we also implement Standard Work when applicable which is about as lean as it gets.

Not Command and Control

The person making the argument also alluded to the fact that they felt the six sigma control phase spoke to a “command and control” mentality more than a kaizen way of life.  They stated, “If the new process is truly better, you shouldn’t have to control people.”

I have practiced six sigma for many years and never once have I seen someone punished for not following instructions post control phase.  This is not to say it has never happened but I have not seen it.  If it does happen, well these people are practicing a different kind of six sigma than I.

As I said, done properly, the control phase is focused entirely on the process – not the people.  This is analogous to the way a lean or TPS practitioner would implement Standard Work during a kaizen event. 

What I Learned

I learned some things from this friendly debate.

First, I learned there is much work to do to close the gap between lean and six sigma.  There are many who feel drawn to one methodology more than the other and thus can sometimes find themselves bothered by something they don’t truly understand.  I am guilty of this as much as the next person as I have attacked MVT on this blog on more than one occasion.

Finally, after some thought and reading Jon’s comments I also learned that I must personally work to promote more of a continuous – kaizen like – mindset when teaching six sigma. 

You see, we must NEVER stop improving a process after implementing the control phase.  Why?  Well it’s quite simple.  I firmly believe it is easier to keep making things a little better than it is to hold gains in place.  Let’s all be honest – plotting control charts can be a little boring while working on improving the process is quite fun! 

Don’t get me wrong we must use things like SPC but it should not end there since that, my lean and six sigma friends, is when things just get started!

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  1. Mark Graban

    August 16, 2007 - 9:22 pm

    Good post, very thought provoking. I suppose SS is just like Lean… it can be misapplied or abused by people who tend to be bad command and control managers, with or without SS or Lean! I’d hope that SS folks are involving employees (rather than the expert just solving problems themselves) and that they focus on continuous improvement.

  2. Ron Pereira

    August 16, 2007 - 9:31 pm

    You know Mark, I thought about coining the term – SSAME – but wanted to check with the lean blog lawyers to make sure there are no copy write issues since you invented LAME!

  3. Rick Foreman

    August 20, 2007 - 8:12 am

    I thought this was a really good post because it brings to the forefront, without really mentioning it, that SS and Lean will not have the sustainment and continuous improvement beyond initial activity unless the people are involved, behavior is changed, and a new culture is established.

  4. Ron Pereira

    August 20, 2007 - 7:18 pm

    Thanks Rick. You summarized the point I was attempting to make perfectly!

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