Quality control is essential to any business. Whether you offer a product, a service or both, your clients expect consistency. You can develop your own approach to quality control, or you or an employee can receive training in Six Sigma. Six Sigma and Lean Six Sigma take a systematic approach to quality control, using data to inform decision-making along the way.


"Sigma" is a measure of deviation in a data set, and "six" refers to the fact that it would take six standard deviation events to occur before the process results in a defect. At six sigma, you can expect 3.4 errors to occur per one million process events.

Why Is Six Sigma Called Six Sigma?

The term “sigma” refers to standard deviation. Standard deviation refers to how a dataset is distributed relative to its mean, or average. The further out data points are distributed, the higher the standard deviation.

The six in Six Sigma refers to the fact that it would take a six-standard-deviation event from the mean for an error to happen. This translates to 3.4 errors out of one million events. A smaller standard deviation would mean more errors and an unacceptable level of quality.

For corporations to be successful, they need to operate with a high level of quality. Two Six Sigma examples include cars and airplanes, which need to be made precisely or they put lives at risk. Even if your product or service doesn’t put someone’s life at risk, operating with as few errors as possible benefits your customers through consistent quality. It also helps your bottom line by minimizing risk.

The History of Six Sigma

The concept of Six Sigma dates back to Carl Friedrich Gauss, a 19th-century mathematician. The bell curve shows normal distribution. Standard deviations create the curves in the bell shape. The Industrial Revolution introduced the idea of mass production, and Henry Ford adapted the assembly line to make mass production a reality.

Errors were inevitable in mass production. Supervisors and managers began measuring errors to control quality. In the 1980s, Motorola shifted from measuring errors per thousand to errors per million in an attempt to improve quality. They created the Six Sigma methodology and used it to save billions of dollars.

Other companies saw Motorola’s success and began to adapt Six Sigma principles. Over time, the concept expanded beyond manufacturing to ensure quality across a variety of businesses.

What Are the Six Sigma Principles?

If you are implementing Six Sigma principles into your business, there are two methodologies you can follow. The methodology varies slightly depending on whether you are implementing a new process or product or improving a process already in place.

If you’re applying Six Sigma to a process already in place, you would use DMAIC, which stands for:

  • Define: Define the boundaries of the project.

  • Measure: Collect relevant data and create a map of all the processes related to your project. 

  • Analyze: Review the data to determine the root cause of the errors. 

  • Improve: Come up with ways to address the root cause and choose one change to test and implement. 

  • Control: Develop methods to monitor and document the process. 

If you need to create a new product or service, you would use DMADV, which stands for:

  • Define: Decide what needs should be addressed by the project. 

  • Measure: Determine the characteristics you need for a successful project. You then put the process into practice. 

  • Analyze: Review the product or service, looking for areas of improvement. Determine the final processes. 

  • Design: Test the product and get feedback from internal and external stakeholders. 

  • Verify: Develop metrics to continue quality testing your product or service. 

What Is Lean Six Sigma?

Lean Six Sigma is a variation on the Six Sigma approach. It combines the quality control principles of Six Sigma with lean enterprise philosophy. Lean enterprise looks at areas of waste within a company and seeks to eliminate those areas. Eliminating waste helps businesses work more efficiently, so these principles naturally complement the quality control elements of Six Sigma.

Lean Six Sigma also has certification levels, which are the same as Six Sigma. Each level of certification shows a more advanced understanding of Lean Six Sigma principles. Those with higher levels of certification provide leadership and mentoring to those with lower certification levels.

How Are Six Sigma Principles Implemented?

Six Sigma principles are implemented using a team approach. A team will typically include professionals with varying levels of experience. Champions serve as leaders and identify projects that align with a company’s mission and goals. Executives provide high-level guidance and support for projects and promote Six Sigma within the company or business.

Other team members support projects according to their experience. Less experienced team members participate in team meetings and assist with improvements. More experienced team members collect and analyze data, develop metrics and provide direction for the project.

What Are Six Sigma Belts?

Six Sigma belts are similar to belts in martial arts, in that each level of belt shows a level of expertise. A white belt is the lowest level and shows a novice understanding of Six Sigma. A master black belt is an advanced team member who provides leadership and training to less experienced team members.

Belts are earned through Six Sigma certification programs. These certification programs are offered by different certification bodies as well as colleges and universities. Each certification has its own requirements, but they all follow a general pattern of needing to show mastery of Six Sigma implementation before achieving a higher belt level. Most of the levels are not laddered, so you don’t have to progress through each level. You can directly work on certification for a green belt, for example, without getting a white and yellow belt first.

Earning a Six Sigma White Belt

A white belt certification indicates that the person is new to Six Sigma. To earn a white belt certification with most organizations, you need to complete introductory training into Six Sigma methods and practices and how those practices can help your organization. Someone with a white belt certification might provide support to a Six Sigma team, but may not be a full participant.

Earning a Six Sigma Yellow Belt

Someone with a Six Sigma yellow belt certification has a basic understanding of Six Sigma. A yellow belt has typically gone through 10 hours or more of training. If you have a yellow belt certification, you may be a full team participant under the direction of a green or black belt. A yellow belt would often be involved with developing process maps and collecting data.

Earning a Six Sigma Green Belt

Green belts are seasoned Six Sigma professionals. To earn a green belt, you need to have participated in a Six Sigma project, complete classroom instruction and pass a written exam. Green belts spend up to half their time on Six Sigma projects, and they participate in data analysis as well as process improvements.

Earning a Six Sigma Black Belt

A Six Sigma black belt requires another level of certification, such as a yellow or green belt. You also need to have completed two Six Sigma projects. Typically, you will also need additional training and to pass a written exam to earn a black belt.

Black belts manage multiple Six Sigma teams. A black belt should be able to teach Six Sigma principles and mentor white, yellow and green belt holders.

Earning a Six Sigma Master Black Belt

A master black belt is the highest level of Six Sigma certification. Master black belts typically have at least five years of experience as a black belt and have completed at least 10 Six Sigma projects. They mentor black and green belts and assist in identifying Six Sigma projects. They work with multiple teams and help to troubleshoot issues and advocate for Six Sigma throughout the company.

Six Sigma project teams need to be well-coordinated. A master black belt would help resolve issues within teams and provide feedback to team members. Someone with a master black belt would be expected to have a high level of interpersonal and communication skills.

Why Get Six Sigma Certified?

Getting Six Sigma certified allows you to demonstrate your expertise. The certification is recognized across industries and typically translates to a higher salary for those who are traditionally employed.

As a business owner, getting Six Sigma certified allows you to establish or continue Six Sigma practices in your business. Six Sigma and Lean Six Sigma are both proven methodologies for improving products and services. Learning the principles gives you a clear path to follow when making improvements in your own business.

Six Sigma also connects you with other professionals who hold the same certifications. You can train with and learn from other seasoned managers and executives, and your certifying organization can support you as you implement the principles in your business.

Choosing a Certification Program

Since there are multiple certifying organizations, it’s essential to select your program carefully. Look for a certification program that has worked with successful corporations. You can find certification providers through The Council for Six Sigma Certification. The Council also has consumer alerts to steer you away from programs that have a less-than-stellar reputation.

The American Society for Quality and the International Association for Six Sigma Certification are two popular options for Six Sigma and Lean Six Sigma Certification. Naturally, there are fees for each level of certification, and the fees increase as you advance through belt levels.