LeanSix Sigma

All the Surveys are Beginning to Whip Me

By Ron Pereira Updated on June 1st, 2007

OK, I need to pick on some Lean friends of mine.  Well actually they may not even know I exist… but I digress.

Anyhow, I was reading an article over at Industry Week (IW) about how Just-In-Time Remains Justifiable.  It’s a good article and you should give it a read.

But they said something that put me over the edge a little.  There have been lots of surveys of late about which continuous improvement methodology is the most popular, how satisfied its users are, etc.  Heck I even commented on one here.  

Well, IW has done a survey like this as has Bain.  Check out the shmula blog for an excellent discussion on the Bain survey.  But while surveys are nice and offer up great water cooler discussion we must keep them in perspective.  

Case in point, in this particular IW article we read this. 

Even so, a statistical profile of IW’s Best Plants finalists in 2006 shows manufacturer confidence in JIT could be waning. In 2006 IW Best Plants finalists said on average 49.6% of their key suppliers provide JIT delivery compared with 50.8% the previous year, 58.4% in 2004 and 77.2% in 2003.

Here is a tip to Industry Week and all those wanting to make statements like this.  There is a thing called “common cause” variation which is normal everyday variation.  If IW and Bain want to do this the right way they would control chart these values to understand if the data are statistically in control or if a “special cause” signal has appeared. 

With only 4 data points stated in the article it will be tough to make any definitive statement otherwise I would control chart it for them.  In fact I did for the fun of it (yeah I have issues) and using these 4 data points the variation is indeed common cause.  Again, I would like more historical data before I jumped up and made any hard statements.

And while it does appear a trend may be developing downward things seem to leveling off.  You don’t need a black, purple, or indigo belt to see that there isn’t much difference between 49.6% and 50.8%!  I mean come on people.  Next year it wouldn’t shock me to see this same percentage jump back up a few points since that is what common cause variation does.  And if this increase, no matter how small, happens I am sure we will hear about how “Lean is really taking off!” 

Let me recommend the book Understanding Variation: The Key to Managing Chaos (2nd Edition) by Donald J. Wheeler to anyone interested in understanding how variation is all around us and ain’t going away anytime soon.  This book is short, concise, and to the point.   Also, you can read my take on control charts and variation here, here, and here.

  1. Tom Skiles

    June 2, 2007 - 12:44 am

    I am with you on this. I am sick of surveys myself.

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