What is Six Sigma?

Every company strives to maintain strong customer retention, keep its employees motivated and happy, and ensure productivity remains high. For decades, businesses, including some of the largest in the world, have used Six Sigma to enhance operations and reduce organizational flaws. Six Sigma is rooted in data, ensuring any business that follows its principles can qualitatively pursue perfection in its processes, improving the quality of products or services and increasing profitability.

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What is Six Sigma?

Six Sigma is a quality-control method designed to help businesses measure and improve product quality by removing defects from any process. It was initially developed in 1986 by American engineer Bill Smith while working at Motorola as a system for boosting the company’s profits. Smith designed Six Sigma as a management technique for increasing productivity while eliminating mistakes. The process lends itself particularly well to industrial entities, including manufacturing and pharmaceutical companies.

Within the first 20 years of its adoption, Motorola claimed $17 billion in savings thanks to this data-driven approach to quality control. Many Fortune 500 companies, such as General Electric and Honeywell, also adopted Six Sigma and reported significant cost savings.

At the core of Six Sigma are several assertions, including:

  • Reducing process variation is essential to business success.
  • Manufacturing and business processes have characteristics that can be defined, measured, analyzed, improved, and controlled.
  • Sustained quality improvement can only be achieved when an entire company, starting with the executive team, are committed to realizing it.

Six Sigma is a scientific method that claims using verifiable data and statistics to make decisions can help businesses achieve measurable profit gains. When the technique is promoted and employed by management, Six Sigma generates tangible improvements to the quality of products and services, increasing customer satisfaction while reducing costs.

Lean Six Sigma

Lean Six Sigma simply means a program that includes “lean” principles in the Six Sigma Curriculum. The majority of Six Sigma programs are identical to their “Lean” Six Sigma counterparts, and this term gained prominence primarily because the military implemented Lean Six Sigma. Some organizations prefer to use the Lean Six Sigma philosophy, particularly those in the public sector or armed forces.

The Six Sigma Methodology

The disciplined Six Sigma methodology is designed to eliminate defects in any business or organizational process. Six Sigma was initially employed in manufacturing companies but has also been adopted by service organizations. Examples of a defect include a delivery of goods taking too long or a manufactured part being too big or small. Generally, a defect occurs when a product or service does not meet the customer’s definition of quality or the physical product requirement.

To be Six Sigma, a process must not exceed 3.4 defects per million (99.99966%) opportunities. Being Six Sigma allows organizations to achieve quantifiable and measurable financial returns from any business process following this methodology. Successful adherence diminishes variation that impacts quality, resulting in a better product or service, improving customer satisfaction, and reducing costs caused by errors.

Six Sigma projects follow two project methodologies, each consisting of five phases. Define, Measure, Analyze, Improve, Control (DMAIC) is the first method and is used for projects aimed at improving an existing business process. There are specific activities and deliverables teams must complete in a given DMAIC project. While the complexity of projects varies, most are finished within four months.

A DMAIC project consists of the following phases:

  1. Define: The first step is identifying the problem, the improvement opportunity, the project goals, and the customer requirements (internal and external). Once the team understands the situation, they must create a map illustrating how they will fix it.
  2. Measure: With the project map in hand, the team must collect data and quantify the problem. This data allows the project team to measure performance and evaluate improvement.
  3. Analyze: Third, use the data to investigate and verify the variables impacting the problem. Identify the relationships between the variables so you can understand cause and effect and determine what is driving the defect at the center of the project.
  4. Improve: In stage four, the team should eliminate the underlying cause of the defect. Doing so requires running experiments to learn how to implement the desired improvements.
  5. Control: Finally, Six Sigma teams must measure performance to ensure the newly improved process is successful. If there are any deviations from the previously targeted improvements, they should be corrected to ensure they do not result in defects. Before the project is complete, a quality control plan must be created to define how the improved process can be maintained at its newly achieved level.

The second project methodology is Define, Measure, Analyze, Design, Verify (DMADV) and is used for projects creating a new product or process or dramatically overhauling an existing one. The five phases of DMADV include:

  1. Define: At the start of a DMADV project, the team sets to clarify the purpose of the project, including identifying goals that align with the organization’s strategy and customer requirements.
  2. Measure: Next, teams have to identify Critical To Quality (CTQ) characteristics and the metrics critical to stakeholder success.
  3. Analyze: Phase three requires developing design alternatives and using them to test the process, product, or design. These tests allow the team to select the best components and create the best design.
  4. Design: In this stage, the team should develop detailed and high-level designs for the new process or product. This phase allows the team to identify unforeseen errors and make additional modifications as necessary.
  5. Verify: Finally, review the new implementation with stakeholders to verify it will be effective once deployed.

Six Sigma Certification Levels

To receive Six Sigma certification, individuals must complete educational and training requirements. They must also display specific professional skills and occupational standards to be eligible. The certifications rank through a belt system similar to the martial arts discipline of karate. Receiving a certificate verifies an individual’s professional skills related to the Six Sigma methodology.

The Six Sigma belt levels are as follows:

  • White Belt: White Belt certification is given to individuals who have yet to complete formal training but are approved to participate in some quality control projects. An individual with a white belt has proven to have a basic comprehension of Six Sigma principles and their application.
  • Yellow Belt: Employees achieve the Yellow Belt ranking after completing Six Sigma basic training in quality improvement. They are approved to support Green and Black Belts on a Six Sigma project.
  • Green Belt: To become a Green Belt, individuals must complete training that teaches them to create process improvement techniques. Green Belts play a vital role in a Six Sigma company, usually responsible for data collection and supporting the Black Belts leading the projects. For certain Six Sigma projects, a Green Belt can also assume a minor leadership role as they have a strong comprehension of the Six Sigma Tools.
  • Black Belt: As the leaders of an enterprise’s Six Sigma team, Black Belts are responsible for overseeing projects and monitoring the work of Green and Yellow Belts. More than anything, Black Belts are responsible for managing the team and ensuring the project reaches its goals on deadline and within scope. They regularly report the team’s progress to the executives. Black Belts should display strong communication skills and have a strong knowledge of financial and statistical analysis, project management, and Six Sigma Tools.
  • Master Black Belt: As the Six Sigma experts in an organization, Master Black Belts have completed all training and exhibit expert-level skills and knowledge. They are responsible for resolving problems during a Six Sigma implementation and training employees who are earning Six Sigma certifications. To become a Master Black Belts, a Six Sigma professional must complete enough improvement projects to be designated an expert in the field. Master Black Belts are often educators, consultants, and technologists in Six Sigma.

Many companies will contract a Master Black Belt to train and coach the internal Black Belts at the onset of a Six Sigma deployment. Additionally, a company should train its senior leadership in sustainable and effective Six Sigma deployment to increase their level of understanding regarding the methods and power of a Six Sigma program. This training will help them more effectively lead and guide the program.

Tools and Techniques for Six Sigma

Under Six Sigma, there are universally accepted and promoted problem-solving tools and techniques professionals should use to complete a successful improvement project. Six Sigma experts use qualitative and quantitative approaches to navigate process improvement efforts.

Standard tools for Six Sigma include:

  • Problem Statement: A fundamental part of the “Define” stage of the DMAIC methodology, a problem statement concisely and factually describes the problem that needs to be addressed.
  • Project Charter: Critical to the “Define” stage of DMAIC and the project’s overall success, a project charter specifies the resources and guidelines the effort requires.  
  • Process Mapping: This exercise shows a Six Sigma team how a project will be completed and visually compares the current process to the new version. It helps communicate the Six Sigma initiative to entities outside the project team.
  • Root Cause Analysis (RCA) methods: These fundamental techniques in Six Sigma are used to identify the root causes of problems.
  • Data Collection Plan: This document describes the exact steps for gathering data and the order in which they must be completed for a given Six Sigma project.
  • Statistical tools such as a Pareto Chart, histogram, and attribute agreement analysis are essential for conducting data analysis to improve quality.
  • Regression Analysis (ANOVA0) and Analysis of Variance (Design of Experiments (DOE)): These statistical techniques are used to compare data sets and are vital to measuring the success of Six Sigma improvements.

Six Sigma Resources

Six Sigma has been an essential element of how large corporations have operated over the past 35 years. Companies worldwide have benefitted from Six Sigma, and many experts and institutions dedicated to this methodology have created resources to teach others about them. Authors Forrest Breyfogle, Thomas Pyzdek, and Michael George have written valuable resources and the American Society for Quality. 

Readers interested in learning more about Lean Six Sigma might benefit from the resources developed by the Lean Enterprise Institute, Toyota Production System for Lean, and authors John Shook, Mike Rother, and Jim Womack. Six Sigma does not have one primary Body of Knowledge as there is for Project Management (i.e., the PMBOK). Still, many useful materials are available to professionals interested in learning more about Six Sigma.


Many of the world’s largest businesses have benefited from Six Sigma, relying on its statistical quality management methods to improve processes, products, and services by removing the causes of defects. Six Sigma is proven to make enterprises better and more profitable while increasing customer satisfaction. Successfully achieving Six Sigma requires long-term commitment throughout an organization, including the most senior leadership. While primarily used by large companies, Six Sigma today offers many tools for small and mid-size organizations. Any company can overcome inefficiencies holding it back through the disciplined Six Sigma approach.

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