Six Sigma

Six Sigma is quality standard of just 3.4 defects per one million opportunities or 99.9996% perfect.

It is also an improvement methodology that emphasizes mathematical and statistical tools to improve the quality of processes that are already under control. Application follows a five-step process of define, measure, analyze, improve, and control often referred to as DMAIC.

Six Sigma DMAIC - define, measure, analyse, improve, control

Motorola conceived the technique in 1986 as a way to achieve the company’s improvement goals in manufacturing and support functions. The term refers to the number of standard deviations a point is away from the mean point in a bell curve. It often is represented as 6σ.

Many lean thinkers apply Six Sigma techniques to solve stubborn quality problems in value-adding processes that already are under control and where an analysis of the overall value-stream has eliminated nonvalue-adding processes.

Six Sigma training programs commonly use belt certifications – white belt, green belt, black belt, and master black belt. Each indicates a higher level of mastery in the use of Six Sigma’s tools.

Lean and Six Sigma

Organizations commonly choose between lean and Six Sigma for an improvement methodology. However, the approaches are complementary rather than substitutive. Six Sigma is a useful methodology, especially when solving difficult quality control problems that require rigorous statistical analysis. However, its reliance on statistical analysis limits the number of people capable of effective practice. Consequently, it can be difficult to scale training. Moreover, it can confine expertise to skilled engineers who are not engaged in frontline operations. Because frontline operators are most familiar with the work and its problems, management should provide skills and authority to solve them. This enables daily continuous improvement. Finally, practitioners may fall into the trap of seeing statistical analysis as the way to solve every problem. However, most problems require far simpler forms of analysis.

Beyond Six Sigma: How Lean Delivers Deeper and More Enduring Benefits

By sharing several specific examples, Art Byrne shares why lean continuous improvement practices are superior to Six Sigma for solving problems and describes the situations where using Six Sigma is necessary. He also discusses why he’s not a fan of belt certification — and the approach he thinks is a better way to teach and learn lean thinking, practices, and tools. In addition, he addresses some of the questions and comments about a Lean Post“Ask Art: How Useful is Six Sigma and the Black Belts and Green Belts that Come with It?” These include:   

  • Why leaders will miss huge opportunities for improvement when they view and use lean practices only as cost-costing efforts.  
  • Why “learn by doing” beats belt certification for developing lean leaders.
  • Why do leaders need to focus on developing a lean culture, not simply applying lean tools?

Additional Resources