Lean People Don’t Say Things Like “Idiot Proofing”


I've long been skeptical of so-called “Lean Sigma” or “Lean Six Sigma.” And not because I'm against Six Sigma statistical methods, which are valid and helpful in solving certain difficult problems.

What I don't like is the oft-stated “Lean Sigma” mantra that says something like, “Lean and Six Sigma are just tools in the improvement toolbox; so use the right tool for the right problem.”

Lean is far more than process improvement tools.

As Toyota people, like Jamie Bonini, would say today, Lean and the Toyota Production System are an “integrated system” that includes:

  • Technical methods
  • Managerial approaches
  • Philosophy
  • People development
  • Organizational culture

Read more here:

So I stumbled across this image that was shared on LinkedIn by a “Lean Six Sigma Master Black Belt,” a term that would imply they know a lot about both Lean and Six Sigma. Or they know a lot about that Frankenstein of a “Lean Sigma” approach:


He added the text:

“it is a waste of time making things idiot-proof, as the idiots are so ingenious they will still find a way to break it!”

I'm not sure who he was quoting. I don't endorse either the image or the text.

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In the Lean approach, we don't call people idiots or dummies. We don't say, or shouldn't say, things like “idiot proofing” or “dummy proofing.”

There's an old Toyota story about how the term “fool proofing” upset an employee, they switched to using the equivalent of “mistake proofing” or “error proofing.” Read more about the story in a comment on an old blog post of mine.

Terms like mistake proofing help us focus on the process and the system instead of blaming individuals. Instead of labeling people as idiots, we have to focus on improving the system so it's easier to do the right thing and harder for errors to occur.

The great book The Checklist Manifesto points out the need to improve systems so smart people (like surgeons) don't make errors or have a bad day. Surgeons aren't idiots. Neither are airline pilots and they use checklists and other systems to prevent errors.

Error proofing is NOT a waste of time. Employees aren't idiots who are looking for ways to cause problems.

We have to be respectful.

There's a risk that people using “Lean tools” from their “toolbox” don't understand or practice the philosophy of Lean that says, in part, that people want to do quality work and that we should respect them and work together, as this quote from former Toyota executive Gary Convis says (a quote I often use in training classes and workshops):

“You respect people, you listen to them, you work together.  You don't blame them.  Maybe the process was not set up well, so it was easy to make a mistake.”

If that mindset is missing from the “toolbox,” then the use of random Lean tools like 5S shouldn't really be labeled “Lean.” If there's an arrogance that creeps into Six Sigma (experts solving problems in complicated ways), then that needs to be kept out of “Lean Sigma.”

Back to the LinkedIn post… an engineer proudly posted this story that made me cringe:

“Something I say way too often. That said, in design and in search of ‘perfection', and what is Six Sigma if not the search for perfection, I see it as an essential function. Sometimes it requires innovation. For example, I knew that in one plant I designed equipment for, the operators were notorious for tampering with machine settings. As such, I added ‘placebo' controls to a machine to satisfy their ‘need' to readjust. At the end, every shift was convinced that their settings worked best. So. in conclusion, sometimes it's important to blend a little psychology with good engineering, to achieve your goal.”

I posted this response:

“Arguably, what you did there wasn't innovative, but perhaps rude and disrespectful to those operators. As an engineer, I'd argue you have an obligation to teach them and work together with them, rather than fool them with placebo controls. Which approach is better in the long term?”

Now, the engineer (thankfully) wasn't labeling what he did as “Lean.” But, he was basically labeling the workers as idiots.

He missed an opportunity to teach the workers about tampering, using lessons from Dr. Deming or his famous “funnel experiment” that shows the impact of overadjustment.

I think an engineer should teach. That's respectful and, I think, better for the organization in the long term. What do you think?

What do you think? Please scroll down (or click) to post a comment. Or please share the post with your thoughts on LinkedIn – and follow me or connect with me there.

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Mark Graban
Mark Graban is an internationally-recognized consultant, author, and professional speaker, and podcaster with experience in healthcare, manufacturing, and startups. Mark's new book is The Mistakes That Make Us: Cultivating a Culture of Learning and Innovation. He is also the author of Measures of Success: React Less, Lead Better, Improve More, the Shingo Award-winning books Lean Hospitals and Healthcare Kaizen, and the anthology Practicing Lean. Mark is also a Senior Advisor to the technology company KaiNexus.


  1. Love how you turned that LinkedIn comment thread into a blog post. Lots of really good points that strike at the cultural core of why Lean implementations fail and how so many people view Lean as nothing more than a set of tools.

    Great work Mark!

  2. From Linkedin:

    Sonia K. Singh — Thanks for this post Mark. I also cringed when I saw the “Idiot Proofing” post the other day. At first I thought it was a joke. Surely an experienced well respected fellow MBB could not think that way about people? Three thoughts came to mind.

    1) It is extremely disrespectful to call employees idiots,

    2) “Mistake Proofing” is actually quite valuable if done right, and

    3) Mistake proofing shows respect for employees by freeing up their time to focus on value added activity.

  3. Just to clear up the origin of that quote – it is a classic “adjust a famous quote to make it look like my own” moment, but inspired by:

    “A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.” – Douglas Adams, Mostly Harmless (1992).

    A pithy quote from a great writer, but a poor philosophy for life.

  4. I think there is a book dedicated to pokayokes from Dr. Shingo that goes into detail about error proofing techniques needs to be mentioned. Although some look at Lean as a individual tools in the box to pick from. The true implications of Lean is to know how to use all the tools simultaneously all the time while you and the teams are continuously looking for better ways of doing everything.

    • Yes, Shingo’s book “Zero Quality Control.”

      I don’t consider poka yoke or mistake proofing to be just a “tool.”

      I think there’s a mindset and a philosophy involved, including “respect for people” and:

      1) People want to do quality work

      2) Don’t put people in a position where they can make mistakes

      3) Managers are responsible for creating a system in which people can be successful

  5. The words you use definitely make all the difference and even if in jest this makes me cringe. I’ve heard people jokingly talk about “slapping them on the wrist” when referring to workers (some highly educated) who aren’t following a process that was created by people who don’t do the work. The assumption gets made that it’s the people who are the problem instead of the system or process. Using phrases like this just perpetuates that mindset.

    I find it ironic that this “Master Black Belt” doesn’t see the contradiction in his own misquote. By definition, a person can’t be both an idiot and ingenious. Maybe all this time he’s been actually Smart-Proofing everything and that’s why it’s not working?

    • Good point.

      It’s quite possible this “Master Black Belt” understands more about statistics than people. Even with a “Lean Six Sigma” belt, most of the LSS programs are 90% Six Sigma with a few superficial Lean tools. These tools can be learned and taught without getting an appreciation for the Lean philosophy and mindset, including “respect for people.”


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