Six Sigma refers to a quality control methodology that takes a systematic approach to improving any type of process. It’s called Six Sigma because the term sigma refers to one standard deviation in a data set. The idea is that six such deviations should occur before the process results in a defect.

When a process achieves Six Sigma, it reaches a point where only 3.4 errors per one million process events result in a defect. It’s an extremely high bar to clear. But Six Sigma provides the tools that allow businesses to achieve that standard.

What is Six Sigma?

Six Sigma is a quality control and process improvement methodology that takes a data-driven approach to solving challenges in any type of operation. Its success rests on the fact that it’s a proven strategy that applies to any type of business.

Practitioners of Six Sigma designed tools that allow project teams to identify the root causes of problems, collect data on how a process currently works, develop solutions to the problem, test those solutions and then put the best option into place. They then measure the results of the change and start the entire process again.

The Importance of Measuring Deviations

The high standard established for Six Sigma is critical for products such as airplanes and cars that require an error-free manufacturing operation.

But even for businesses where the product is not a matter of life or death, achieving Six Sigma remains a worthy goal. A consistent product that meets customer expectations over a long period of time will lead to a healthier bottom line and growth in the customer base. Continuously improving operations also minimizes the risk for a company.

Companies that have applied Six Sigma include Amazon, 3M, Bank of America, Caterpillar, and Starbucks.

Six Sigma in Practice

In order to reach Six Sigma, any type of organization must undergo a thorough examination of the issues that are causing processes to result in mistakes, defects in the final product or wasteful action (Lean Six Sigma, in particular, focuses on waste).

Such evaluations require teams to assess current operations by first using Six Sigma tools such as a Value Stream Map to provide a visual representation of every detail of an operation. They then use a different set of tools, such as the 5 Whys or a Fishbone Diagram, to determine the root cause of mistakes, defects and waste.

Much of what happens in a Six Sigma project falls under the most popular approach in the methodology, called DMAIC. It’s an acronym for define, measure, analyze, improve and control.

The Importance of DMAIC

DMAIC is a data-driven strategy used to continuously improve processes. Each letter in the name stands for a process phase. They typically include the following steps.

  • Define: The project team defines the problem they want to solve. This includes developing a project charter, detailing customer needs and requirements and developing a process map.
  • Measure: The team collects data on the current operation and determines the baseline sigma.
  • Analyze: The team analyzes the data and determines the root cause of the problem through data and process analysis.
  • Improve: The team generates potential solutions to the problem. They select and implement the solution that will work best.
  • Control: To maintain the benefits from the solution, the team designs a control plan to ensure the new strategy is correctly put into place.

The Belt System in Six Sigma

The DMAIC process and other Six Sigma strategies help companies move systematically toward achieving Six Sigma. However, getting there requires people with detailed understanding of how to assess a challenge and who know the right tools for each situation. That is why companies increasingly encourage and support employees in earning a Lean or Six Sigma belt certification.

As in the martial arts, Six Sigma belts are color-coded. Each color represents a new level of knowledge and skill in Six Sigma.

Six Sigma White Belt: White Belts complete several hours of Six Sigma training that teach them the basics of Six Sigma.

Six Sigma Yellow Belt: Yellow Belts get 10 to 15 hours of training that gives them enough knowledge to work in areas such as creating process maps and gathering data.

Six Sigma Green Belt: Green Belts often work as the backbone for a project team, doing much of the day-to-day work. Green Belts may spend 25 percent to 50 percent of their work time on Six Sigma projects.

Six Sigma Black Belt: Black Belts work full-time on Six Sigma projects. They not only have training, but also must work successfully on at least two Six Sigma projects at the Green Belt level to earn a Black Belt. They also must pass a written exam.

Six Sigma Master Black Belt: A Master Black Belt is the highest Six Sigma belt ranking. Master Black Belts must have five years of experience as a Black Belt and successfully complete at least 10 Six Sigma projects. They typically oversee a company’s Six Sigma efforts, working directly with senior executives.