While ancient Greek mythology is drawing audiences to theaters, a different kind of mythology is playing out across manufacturing floors and other industry operations. It’s the myth that lean is about velocity and Six Sigma is about quality.

In this episode of Behind the Curtain: Adventures in Continuous Improvement, podcast cohosts John Dyer and Dr. Mohamed Saleh tackle this tale as they continue their series on myths surrounding lean and Six Sigma.

“If lean was about speed and Six Sigma was about quality, why did Toyota become famous for building some of the highest quality vehicles?” asks Saleh at the top of the show. “When you hear the success stories of … what brought them to the spot, what brought the Toyota Production System to the spotlight, it was primarily about their quality.”

Saleh takes issue with the notion that lean is about speed. “The reality is lean is about creating value, and that's through the elimination of waste,” he says.

Moreover, he adds, “I've never read a book that … I heard a person from Toyota say, ‘Go faster.’ They do say remove what prevents smooth flow. And in my opinion, there's a huge difference.”

Dyer questions whether Toyota would embrace the words lean or Six Sigma. “I think they would say it's Toyota Production System,” he says.

Dyer says he avoids using the words lean and Six Sigma.

“I like to call it team-based continuous improvement because it involves everything,” Dyer says. He points out that you could make the argument that among the wastes lean addresses are quality defects.

“In that regard, quality is a main component of lean and the ability to get rid of waste,” he notes. On the other hand, he adds, Six Sigma is necessary to understanding variability.

“On the lean side, if you try to address the quality-defect waste without having a full understanding of how variation works and the different types of variation—common cause and special cause, and who's responsible for addressing those variability wastes—then you're not going to be very successful in improving your quality,” Dyer says.

During the discussion, Saleh points to a host of lean tools and philosophies that he says address quality, such as standard work and quality at the source. He describes lean as an umbrella term that encompasses quality, while “I don’t see Six Sigma as an umbrella.”

Dyer disagrees, arguing that Six Sigma is more than simply tools, while agreeing that it is not as encompassing as lean is.

The two hosts delve into the histories of lean and Six Sigma and discuss events that triggered the apparent need to create a division and rivalry between the two.

Dyer shares a real-world example of the integrated use of lean and Six Sigma, and argues that continuous improvement principles are more important than labels.

“This whole myth of one's this and one's that, I think that's a waste of breath,” Dyer says.

Saleh discusses a client he worked with who was against using the terms lean and Six Sigma.  

“We sat down with his leadership team and talked about what are our values for the company, and then we talked about what [are] the guiding principles that we want our company to stand for,” Saleh says. While many reflected a lean perspective, the term lean was never used, he said.

Saleh closes out the episode with a strong lean emphasis. “Lean is far from just being velocity. It's about flow, and quality at the source is one of its guiding principles.”