What is Six Sigma?

Six Sigma is a quality management methodology used to help businesses improve current processes, products, or services by discovering and eliminating defects. The goal is to streamline quality control in manufacturing or business processes so there is little to no variance throughout.

Six Sigma was trademarked by Motorola in 1993. The name references the Greek letter sigma, which is a statistical symbol that represents a standard deviation. Motorola used the term because a Six Sigma process is expected to be defect-free 99.99966% of the time — allowing for 3.4 defective features for every million opportunities. Motorola initially set this goal for its own manufacturing operations, but it quickly became a buzzword and widely adopted standard.

Six Sigma is specifically designed to help large organizations with quality management. In 1998, Jack Welch, CEO of GE, helped thrust Six Sigma into the limelight by donating upwards of $1 million as a thank you to the company, recognizing how Six Sigma positively impacted GE’s operations and promoting the process for large organizations. After that, Fortune 500 companies followed suit and Six Sigma has been popular with large organizations ever since.    

Six Sigma principles

The goal in any Six Sigma project is to identify and eliminate any defects that are causing variations in quality by defining a sequence of steps around a certain target. The most common examples you’ll find use the targets “smaller is better, larger is better, or nominal is best.”

• Smaller is Better creates an “upper specification limit,” such as having a target of zero for defects or rejected parts.
• Larger is Better involves a “lower specification limit,” such as test scores — where the target is 100%.
• Nominal is Best looks at the middle ground — a customer service rep needs to spend enough time on the phone to troubleshoot a problem, but not so long that they lose productivity.

The process aims to bring data and statistics into the mesh to help objectively identify errors and defects that will impact quality. It’s designed to fit a variety of business goals, allowing organizations to define objectives around specific industry needs.

You’ll also find similar principles in Lean Six Sigma, which combines the principles of Six Sigma with the Lean methodology. Incorporating Lean into Six Sigma brings a heightened focus on reducing waste, defects, and variance, while also staying ahead of schedule and under budget. This lean methodology helps organizations stay more agile and flexible while also focusing on establishing long-term processes. Lean adds a stronger focus to defects, overproduction, waiting, nonutilized talent, transportation, inventory, motion, and extra-processing. The idea is that by solving these issues, companies can solve problems faster, improve efficiency, and boost productivity.

Six Sigma methodologies

In practice, Six Sigma follows one of two sub-methodologies: DMAIC and DMADV:

Six Sigma DMAIC: The Six Sigma DMAIC project methodology includes five phases, each represented as a letter in the DMAIC acronym. These include:

• Define the problem, the customer, the project requirements, and the ultimate goals and expectations of the customer. During this phase, projects are selected, research is conducted to determine various opportunities and possibilities, and the scope of the project is established.
• Measure performance of the current process by establishing a data collection plan to determine defects and gather metrics. At this stage, it’s important to establish performance baselines, future goals, and how performance will be measured.
• Analyze the process to establish root cause of variations and defects to identify issues with the current strategy that stand in the way of the end goal. During the analyze phase, it’s important to use data to identify parameters and inputs that have the most significant impact on the final process.
• Improve the process by eliminating root causes of defects through innovative solutions. During the improve phase, the focus is on testing the best potential solutions identified in the earlier phases. It’s important to consider performance, cost, implementation demands, and risks or disruptions that may arise.
• Control the new process to avoid falling into old habits and to ensure it stays on track. During this final phase, all changes made to the process are documented, the root cause of every problem is explained, and a schedule is established for continued monitoring.

Six Sigma DMADV: The Six Sigma DMADV framework, also known as the Design For Six Sigma (DFSS), includes five stages:

• Define realistic goals that suit customer requirements or the business strategy. In this stage, project goals are established, schedules and guidelines are drafted for review, and risks are identified. A clear plan for the project should emerge by the end of this stage, and the overall strategy should be aligned with customer expectations.
• Measure and identify the customer’s critical to quality (CTQ) requirements and translate these into project goals. During this stage, the team identifies requirements, market comparisons, key design elements, and any necessary design components for the project. By the end of this stage, it’s important to have a set of metrics for aligning with customer requirements and overall project goals.  
• Analyze multiple options and alternatives for the customer along with the estimated total life cycle of the project. This stage is all about building conceptual designs, identifying the best requirements and components, and determining the total cost of the project. The analyze stage is intended to set up the project with a defined design option that can be tested and prototyped.
• Design the process at a high level before moving onto a more detailed version that will become the prototype to identify errors and make modifications. During the design stage, the final details of the design are established, and a model is built that is one step away from a functioning prototype.
• Verify that the final iteration of the product or process is approved by all customers and clients — whether internal or external. The final design is presented to all the key stakeholders to ensure that it’s the right fit and that it will be effective in real-world use cases. This is the stage where you’ll document the process, all changes, and plans to implement the process so that it’s scalable and sustainable.

DMAIC vs. DMADV: The DMAIC and DMADV methodologies seem similar, but they have different use cases. The DMAIC methodology is designed for existing process or products that aren’t meeting customers’ needs or performing to standards. When a business needs to develop a product or process that doesn’t already exist or when a product has been optimized but still falls short, that’s when you want to use DMADV.

Determining a Six Sigma project

To find projects in your organization that would benefit from Six Sigma they need to fit some criteria:

• Each project needs to have a clear process of inputs and outputs.
• Don’t go into the project with a pre-determined solution — that means you already know the fix.
• Focus on reducing “operation variation” to make it easier for untrained operators.
• Project needs to be approached with knowledge of variations in process inputs and how to control and eliminate defects.

iSixSigma offers the example of a “slow cycle time at Station 30” due to defective parts coming from “Station 20.” A “non-Six Sigma solution” would attempt to rebalance the assembly line, while re-doing the work, keeping cycle time low and not spending on labor. A Six Sigma solution would be to “investigate and control key inputs that contribute” to defective parts coming from Station 20 to keep it from happening again in the future. In this case, the Six Sigma approach focuses on proactively eliminating the defect, while a non-Six Sigma approach simply reacts to the problem without identifying the cause.   

For a closer look at where to apply Six Sigma, see “How to find the perfect project for Six Sigma success.”

Six Sigma implementation roles

A key concept in Six Sigma is the idea of establishing clear leadership roles and a hierarchy for quality management. The key roles for Six Sigma implementation include:

• Executive leadership: This includes the CEO and other executive management who are charged with developing the vision for Six Sigma implementation. Leaders should also be responsible for encouraging new ideas and supplying the resources to act on innovation.
• Champions: Typically found in upper management, Champions are the people responsible for acting on executive leadership’s vision and acting as mentors to Black Belts.
• Master Black Belts: These workers spend all their time on Six Sigma methodology, either by guiding Black or Green Belts or helping Champions. They’re picked out by Champions and are tasked with ensuring consistency in the Six Sigma strategy.
• Black Belts: Working below Master Black Belts, Black Belts are responsible for executing on the Six Sigma strategy and typically act as leaders for specific tasks.
• Green Belts: Guided by Black Belts, Green Belts are new to the Six Sigma methodology and start learning it while maintaining their other job responsibilities.

You may find other belts — like White, Yellow, and Orange. These are adopted by organizations to represent employees with some Six Sigma training but aren’t involved in the overall project.

Six sigma certification and training

Typically, Six Sigma certification and training is offered directly by businesses, with GE and Motorola paving the way by being the first to develop Six Sigma certification programs to verify proficiency in the Six Sigma methodology. Large companies and universities soon followed suit, offering their own versions of a Six Sigma certification program.

However, there isn’t much oversight to what qualifies as Six Sigma certification and the criteria for Green Belt and Black Belt certifications can vary. Certification programs are offered through businesses, universities, professional associations, and for-profit training organizations. Some notable organizations include:

• Accenture
• American Society for Quality
• Boston University
• Cornell University
• Dartmouth College
• GE
• IASSC
• Motorola Solutions
• Purdue University

Some organizations offer Six Sigma accreditation. For example, the IASSC offers Lean Six Sigma credentialing and accredited training providers. The Council for Six Sigma Certification also offers a list of accredited Six Sigma providers. Ultimately, when choosing a Six Sigma certification or training program, it’s important to do your research to ensure the organization, university, or third-party vendor offers the right training for your needs and has the right qualifications.

For more IT management certifications, see “17 IT management certifications for IT leaders.”

More on Six Sigma:

• How to find the perfect project for Six Sigma success
• Six Sigma for Better IT Operations and Customer Satisfaction
• Lean Six Sigma: Process improvement with a purpose
• 7 Reasons IT Organizations Should Adopt Six Sigma
• Lean + Six Sigma: Process Improvement Needs to Know Its Place

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