A process that produces conforming parts «most of the time» is costly: scrap, rework, sorting, and customer complaints. The problem rarely stems from a lack of effort. It stems from the variability : The same machine, running the same program, never produces exactly the same part twice.
Six Sigma is a structured approach to reducing this variability in a measurable and sustainable way. It is based on a step-by-step method—DMAIC (or DMAICS)—statistical tools, and a dedicated organizational structure with well-defined roles: Champions, Black Belts, and Green Belts.
This article explains what Six Sigma is, the step-by-step process of a project, the roles required for its implementation, and the appropriate training for each role.
What is Six Sigma?
Six Sigma is a quality improvement methodology that originated at Motorola in the 1980s and was later popularized by General Electric in the 1990s. Its name comes from the Greek letter σ (sigma), which refers to the standard deviation, a statistical measure of dispersion.
The stated goal is ambitious: a «Six Sigma» process has such a narrow variation relative to its tolerances that it produces virtually no defects. By convention, this is associated with 3.4 defects per million opportunities, taking into account possible process drift over time.
Beyond the numbers, Six Sigma is based on three principles:
- make decisions based on facts and data, not on impressions;
- address the causes of variability, not just its symptoms;
- drive improvement through a project-based approach, with specific targets, a clear methodology, and clearly defined responsibilities.
Six Sigma and Lean: Two Complementary Approaches
Lean aims to eliminate waste and streamline processes. Six Sigma aims to reduce variability. The two naturally complement each other in the Lean Six Sigma. A fast production line is worthless if it produces nonconforming parts, and a well-controlled process loses its value if it is overwhelmed by demand and inventory.
The DMAICS Approach: The 6 Steps of a Six Sigma Project
The international method is known by the acronym DMAIC : Define, Measure, Analyze, Improve, Control. In France, Maurice Pillet popularized a variation, the DMAICS, which adds a sixth step: Standardize. It is essential to ensure that the benefits of a project are not limited to a single machine or a single workshop.
By strictly following these steps, a technician who is not an expert in statistics can, with the appropriate training, achieve the specified variability target.
1. Define
We define the scope of the project:
- What is the problem, and what is its scope?;
- What impact does this have on the customer and the company?;
- What specific target, and by when?
The deliverable is a project charter, approved by the Champion. A good definition helps avoid the most common pitfall: a project that’s too broad and runs out of steam.
2. Measure
We are collecting reliable data on the current situation. Two questions guide this step:
- Is the measurement system capable? A study R&R bonus verifies that the measurement's dispersion is small compared to that of the process.
- How is the process performing right now? It is encrypted using capability indicators (Cp, Pp, Ppk).
3. Analyze
We identify the root causes of variability. To do this, we use graphical tools (histograms, scatter plots, Pareto charts) and the statistical testing. They help distinguish between true influencing factors and false leads: a batch of material, a team, a tool, or a setting.
4. Innovate
We identify and validate solutions. When multiple factors interact, the experimental designs allow you to find the best setting with a minimum number of trials. The solutions are tested on a small scale before being implemented on a larger scale.
5. Check
We ensure that the improvement is sustainable. Control charts and monitoring SPC detect any deviations before they result in nonconforming parts. Monitoring plans and operating procedures are updated.
6. Standardize
We build on our achievements. Best practices are extended to similar processes and sites, standards are formalized, and lessons learned from the project are shared. It is this step that transforms a one-time success into sustainable progress for the company.
Six Sigma, a management approach
Six Sigma isn't a one-time effort. To be successful, it must be a a genuine business strategy, supported by an organization and visible commitment from management.
Six Sigma management is a project-based approach to management. Work groups bring together people from different departments and organizational levels. They therefore require a matrix management structure, which complements the usual hierarchical structure without replacing it.
Roles in a Six Sigma deployment
The steering committee
It brings together the company’s chief executive and all the Champions. It is sometimes confused with the executive committee. It is still necessary to schedule regular meetings dedicated to reviewing project progress in order to maintain momentum and resolve any issues.
It relies on four tools:
- a plan for implementing the Six Sigma program;
- a project tracking tool;
- a tool for measuring results;
- a means of communication for sharing strategic objectives.
The Champions
These are high-level executives who are personally involved in Six Sigma. Their role is both strategic and tactical:
- ensure the successful rollout in their sector;
- select the projects to launch;
- monitor progress by conducting milestone reviews;
- ensure that resources remain available;
- organize the recognition of contributions.
Master Black Belts
They oversee all Six Sigma projects within a business sector. They train Black Belts, support them in their projects, and participate in reviews.
They have a thorough understanding of all aspects of Six Sigma, from statistical tools to more conceptual elements. They are typically former Black Belts who have successfully completed numerous projects. In smaller organizations, an external consultant may fill this role.
The Black Belts
They lead complex Six Sigma projects. Their authority is matrix-based rather than hierarchical—much like that of a team captain—and is rooted in their expertise, commitment, and ability to bring people together. They are the ones who select the tools, conduct the analyses, and mentor the Green Belts.
The Green Belts
They lead smaller-scale projects, often within their own department, or participate in Black Belt projects. They serve as the liaisons for the initiative on the ground: technicians, supervisors, and process or quality engineers.
The Yellow Belts
They understand the fundamentals of the process and the DMAIC framework. They actively participate in working groups and apply the method to simple problems.
The Project Group
A Six Sigma project is a team effort. Depending on its scope, the team consists of 3 to 10 people with cross-functional skills. They are chosen not only because they share an interest in the subject but also because they approach it from different perspectives. The goal is to create an environment that fosters creativity and enables consensus-building.
Which Six Sigma training program is right for which role?
| Role | What he does | Tailored Training |
|---|---|---|
| Member of a working group | Participates in projects, solves simple problems using the DMAIC process | [Yellow Belt Lean Six Sigma]([Yellow Belt URL]) |
| Technician, supervisor, engineer | Lead a Six Sigma project from start to finish | [Green Belt Six Sigma]([Green Belt Six Sigma URL]) or Green Belt Lean Six Sigma |
| Complex Project Manager | Leads cross-functional projects and provides support to Green Belts | [Black Belt Six Sigma]([URL Black Belt Six Sigma]) or Black Belt Lean Six Sigma |
| A team to be built over time | Develop skills across multiple levels and tools | Unlimited Training Package |
Ellistat training courses are based on Maurice Pillet’s methodology. They are available as e-learning or blended learning courses and lead to certification in partnership with the Lean Six Sigma University. The exercises are conducted using the Data Analysis software, allowing participants to apply each statistical tool to real-world scenarios.
To gain a deeper understanding of a specific tool, targeted training courses round out the program:
- Process Control : capability and control charts;
- Experimental Design ;
- 8D problem solving.
Mistakes That Cause a Six Sigma Program to Fail
- A rollout without management support. Without Champions involved, projects take a back seat to day-to-day emergencies.
- Projects that are too ambitious. A poorly defined scope during the «Define» phase causes the project to drag on indefinitely.
- Neglect the measurement. Analyzing data from an unreliable measuring device leads to false conclusions.
- Skip the "Check" and "Standardize" steps. Without monitoring or maintenance, the process reverts to its initial state within a few months.
- To teach without having students practice. A Green Belt or Black Belt training program should culminate in a real project that addresses a real business problem.
Conclusion
Six Sigma It is not just a statistical toolkit. It is a management approach that combines three elements:
- a rigorous method, DMAICS;
- a clear organizational structure, from the steering committee down to the Green Belts;
- a requirement for data-driven decision-making.
When implemented effectively, it can sustainably reduce process variability and the cost of non-quality. The starting point is often the same: train a few key individuals to the appropriate Belt level and assign them their first high-stakes project.
FAQ
What does Six Sigma mean?
Sigma (σ) refers to the standard deviation, a measure of dispersion. A «Six Sigma» process has such low variation relative to its tolerances that, by convention, it produces 3.4 defects per million opportunities. By extension, Six Sigma refers to the approach aimed at achieving this level of control.
What is the difference between DMAIC and DMAICS?
DMAIC (Define, Measure, Analyze, Innovate, Control) is the internationally recognized method. DMAICS adds a sixth step—Standardize—to extend solutions to other processes and ensure long-term benefits. This variation was popularized in France by Maurice Pillet.
What is the difference between Green Belt and Black Belt?
Green Belts lead projects with a limited scope, often within their own department, or participate in larger projects. Black Belts manage complex, cross-functional projects, are proficient in more advanced statistical tools, and provide guidance to Green Belts.
Do you have to be a Green Belt to become a Black Belt?
Not necessarily: Depending on your background and experience, you may be able to enroll directly in certain Black Belt courses. However, having led your first project as a Green Belt remains an excellent foundation.
What is the difference between Six Sigma and Lean Six Sigma?
Six Sigma focuses on reducing variability. Lean Six Sigma adds Lean tools—which are geared toward eliminating waste and ensuring smooth flow—to address both quality and performance.
💡 Want to launch a Six Sigma initiative or help your teams build their skills? Discover our Yellow, Green, and Black Belt certification courses, based on Maurice Pillet’s methodology and available via e-learning. View all our training courses