What Is Six Sigma Methodology? Processes & Principles Guide

Last Updated:Wednesday, June 14, 2023

Cutting to the chase: just what is Six Sigma methodology? Six Sigma is a project and work methodology that’s all about reducing variables in your processes and deliverables. Unlike other lean methodologies, the main focus with Six Sigma is less about cutting costs and more about streamlining work.

This article will go into a more detailed definition of Six Sigma, and then look at some of its tools, certifications, methods, stages & steps, and guiding principles. We’ll also give examples of Six Sigma and talk about the pros and cons of Six Sigma. Let’s go.


What is Six Sigma methodology? Our definition

The Six Sigma methodology focuses on improving business processes by eliminating wasteful or unnecessary steps. One can say that the Six Sigma definition centers on producing deliverables with as few mistakes or variations as possible. 

In other words, Six Sigma is a methodology which uses statistics and data in order to achieve continuous business process improvement. Customer satisfaction is one of the highest goals of Six Sigma. 

A glance at our project management methodologies comparison will show Six Sigma ranks among the top. It is particularly favored by larger businesses and in the construction sector, where it’s important to manage the costs of material infrastructure.

And whereas project management body of knowledge (PMBOK) method aims at ensuring project success on a general scale, Six Sigma focuses on streamlining specific aspects of the project. This also differentiates it from Critical Path Method, which deals with the envisioning and planning out of project scope writ large.

To get into the details of Six Sigma, you need to know about standard deviations, otherwise associated with statistical bell curves. This refers to a standard or desired result from a process, and it describes how far from this one result, or range of results, one can expect, that is, how much one can deviate from this result. 

For example, if you are manufacturing blueberry muffins with a standard muffin containing 8 blueberries, and you have a standard deviation of 2, that means on average your muffins will have the standard number of blueberries plus or minus 1 blueberry, meaning most muffins will have between 7 and 9 blueberries.

The Six Sigma abstractly refers to the standard deviation of 6, that is, 3 above and 3 below. Six Sigma projects aim to limit the deviations as much as possible to a sigma of 6, which is why Six Sigma is so important for quality management. Although today, the exact number of 6 is less important than the overall methodology.

Six Sigma statistical tools

In general, there are about 6 statistical management tools that project teams use for process mapping and quality improvement. They are:

  • Cause and effect analysis

  • Flow charts

  • Pareto charts

  • Histogram

  • Check sheet

  • Scatter plot

  • Control chart

Cause and effect analysis

When something goes wrong, that is the effect of a cause, and therefore cause and effect analysis is central to Six Sigma problem solving. To analyze cause and effect, you need to identify the problem, make clear the factors and context, identify possible causes, and propose solutions.

Flow charts

Flow charts are good visualization tools to show you work current processes and are therefore useful in Six Sigma. Flow charts can clearly show you the steps involved in a process, the inputs, outputs, events, and the individual and connected operations.

Pareto charts

A Pareto chart is a chart that is a combination of a bar graph as well as a line graph chart, showing the relationship between individual values and a cumulative total. This is useful in Six Sigma for identifying problems and defects, how often they occur, and how much they might be costing your operation in terms of time or money.


A histogram is another tool for Six Sigma which shows you visual charts that represent distributions and can also show you deviations, especially within specified time intervals. It’s used to see how frequently an event occurs at different stages of a process.  

Check sheet

A check sheet is a form you use to collect and display data. In a Six Sigma process, you use the check sheet at the location where the work and its corresponding data collection is taking place. It is also used in lean Six Sigma.

Scatter plot

A scatter plot is another cartesian diagram. It shows the relationship between two different data sets operating in the same existing process. In Six Sigma, this shows what happens to one process and its set of data when changes are made to another.

Control chart

Control charts are more visual tools to show us how data changes over time throughout a process. As a Six Sigma tool, it is good for establishing upper and lower boundaries to a standard deviation, and to see how a system reacts to variations over time.

Six Sigma certifications

There are many Six Sigma global institutes. You can get official Six Sigma certification from these institutes when you display a certain mastery and excellence in implementing Six Sigma practices. There are also many places you can go to do a Six Sigma training as part of a certification program in order to become a certified Six Sigma practitioner. 

Like karate, the roles of Six Sigma experts are broken down by levels of colored belt certification. They are:

Six Sigma while belt

Six Sigma white belt certification is the lowest level. A white belter should be great at problem solving and brainstorming, though white belts aren’t necessarily always part of the team.

Six Sigma yellow belt

Yellow belt certification means you are most likely always part of the team. You could be a problem solver, but mostly you are good at evaluating things and proposing solutions. 

Six Sigma green belt

Green belt certification could mean that sometimes you are a team leader with so-called green projects, which are lesser in scope or priority than black belt projects. Green belters can also be part of a black project team, often in data analysis.  

Six Sigma black belt

Black belt certification means you are a team leader. You often lead projects that are heavily problem-solving oriented. Black belters are also useful for training new team members and team coaching.

Six Sigma master black belt

The Six Sigma master black belt is the highest level of Six Sigma expertise. Master black belts will train both green belts and black belts to lead teams and projects, and be their coaches. Six Sigma master black belts must be also highly skilled and knowledgeable about their area of expertise. 

Who created Six Sigma & when was the Six Sigma approach developed?

The Six Sigma methods, as capitalized, was created in 1986. Bill Smith is the man who gets the credit for this. Smith was an engineer who worked for Motorola at the time. The motivation was that Smith had wanted to consolidate ideas about his work process improvement methodology.

Six Sigma gained more prominence in 1995. This was when the CEO of General Electric, Jack Welch, made it a core aspect of his business management method for improvement projects throughout GE.

When is the Six Sigma method appropriate?

The importance of Six Sigma has only grown, from Smith's design of it to Welch's championing of it. But knowing something is good or important doesn’t tell you how to use Six Sigma, and when it’s appropriate.

Six Sigma is appropriate and very useful for many things. It is great for when you have problems that are not very clear, or where you have projects whose goals are only vaguely defined. It’s also a useful method for when you are completely facing a total unknown in your approach. Finally, it’s appropriate if you need to make some improvements fast or on a budget.  

Six Sigma examples

Now how about two of Six Sigma examples in some known industries.

First Six Sigma example: Healthcare

In healthcare, the patient is the customer, and so satisfaction could be a matter of life and death. Six Sigma in healthcare can help clinics and other facilities cut down on patient wait times through a more streamlined administration of supplies, staff and spacing, among other things.

Second Six Sigma example: Software development

Six Sigma is very common for coders, programmers and software engineers. It can be used for simple bug tracking and issue management, or for testing and continuous rollout of upgrades to a platform. With Six Sigma, developers can ensure a better customer experience by leveraging data.


2 Six Sigma processes & the 5 Six Sigma steps belonging to each

There are two Six Sigma practices, otherwise known as Six Sigma methodologies, and each have five Six Sigma stages. These are not too dissimilar from the steps in what is known as SPC, or statistical process control, which mainly deals with doing quality control through data.

When implementing Six Sigma, it’s a good idea to know beforehand which of the following practices you should use.  

The DMAIC process of Six Sigma

The first method of the Six Sigma phases is called DMAIC, which is an acronym for: Define, measure, analyze, improve and control. 

The main idea here is that DMAIC is good for improving your projects, whether these be a manufactured good or a service you provide. It’s a way of articulating project management guidelines in a proactive, data-driven manner, with the outcome of your work always geared towards better customer satisfaction. 

One can also say that DMAIC is a very reactive strategy, as it is best used for quickly adapting to changes and fixing problems after they’ve arisen.


Define what exactly you want to improve in your product, or lay out in clear terms what the problem is that needs to be solved. You can even do a project scope or project timeline in this Six Sigma stage, and make clear your overall business strategy.


At this second DMAIC Six Sigma phase, you figure out how you will collect and measure your data related to your project, as in with what metrics like work cycle times or costs. Then you begin collecting your data. You’ll also be taking into consideration factors like customer requirements, risks and other critical design parameters.


The analysis stage of DMAIC Six Sigma is to identify the cause of a problem or the solution to how it can be improved. If there is more than one problem, it’s key to list and prioritize them, as well as specify the inputs and outputs of the data contributing to your understanding of the causes.


In the improvement stage of DMAIC Six Sigma, you begin to map out solutions and the actions to take. This stage can begin with brainstorming and end with a clear to-do list. You want to be creative, but also you want to avoid project creep so keep things simple.


In the control stage, you want to see how well your changes meet your plans, and more importantly, if this new improved project or product can be sustained consistently going forward.  

The DMADV Six Sigma process

The second methodology of Six Sigma implementations is called DMADV, and it is an acronym for: Define, measure, analyze, design and verify. 

The difference here between DMAIC and DMADV is that while the former is about improving a product or solving a problem with it, the latter is about improving a process. DMADV can streamline the workflow by improving an existing process or for discovering and trying new work processes. 

Another difference is that DMADV is better for preventing problems before they arise because it can be more proactive.


As before, here is where you identify problems like bottlenecks or wasted resources. Right from this very first stage you should have clear goals in mind, and ones that never fail to consider the end user or customer.


In the measure stage of DMAIC Six Sigma, you will often get ready to sort your data using visualization tools like CTQ or critical to quality tree charts. These demonstrate the linkages between an improved process and customer satisfaction with their requirements and tasks that must be done to complete the project.


Like DMAIC, the first three stages of DMADV are the same. Here, you might begin to analyze new processes or modifications to your current existing process. You’ll have to think about constraints, components and participants going forward, especially if you are proposing several alternatives.


In the design stage of DMADV Six Sigma, you should finally decide on a single option from your many alternative solutions. This could also be the stage where you begin to design highly data-driven experiments.


At the verify stage of DMADV Six Sigma, it’s a good idea to get all the stakeholders together. Everyone from the team working to the customer, to see if all agree that the selected design matches the expectations set out in the define stage. If all is well, this stage must have a plan to keep the new process implemented in a sustainable way.  


What are the 7 Six Sigma steps?

Aside from choosing DMAIC or DMADV with their 5 stages in Six Sigma, you can also break down doing a Six Sigma project into 7 steps. These steps aren’t meant so much as to replace the 5 stages mentioned above, but to offer a secondary perspective which can function alongside one another, or be superimposed onto each other.

The 7 Six Sigma steps are:

  1. Initiate

  2. Plan

  3. Team up

  4. Prioritize

  5. Assign ownership

  6. Root cause analysis

  7. Execute and monitor


The first step is where you gather all the stakeholders involved. You show the benefits of running the program by demonstrating where you can cut losses or defects.


Step two of Six Sigma is the time to make a project plan. Decide what tools, especially apps, everyone will use, and plan to get resources according to the project requirements.

Team up

The Six Sigma higher level belts will gather their teams in the third Six Sigma step. Here it’s important to make sure everyone is aware of the Six Sigma process to be followed.


The fourth Six Sigma step is where you figure out priorities. You also make a quality control chart, which can lay out things like acceptable standard deviations.

Assign ownership

Six Sigma step number five is for figuring out everyone’s roles on the projects. You want to assign ownership to products and other roles like scrum master.

Root cause analysis

The root cause analysis part of Six Sigma is an important step. It’s where you think about not only fixing a problem but looking for the reason it happened and preventing it from happening ever again. 

Execute and monitor

The final step of implementing Six Sigma is about running the project, monitoring its progress, and looking for ways to enact continuous improvement. 


The 5 Six Sigma principles

What are Six Sigma principles? They are less about stages or phases or steps, and it’s also not about processes or methodologies. The principles of Six Sigma are more about having the right mindset. 

There are 5 of them, which we’ll talk about in this section. These principles should guide every single one of your decisions, approaches and reactions throughout the Six Sigma process. What are 

Customer satisfaction

The sole purpose of all project management is to bring maximum value to your customer in terms of the product you deliver as well as the overall customer experience. Your customer’s satisfaction is the bottom line. Think always of the customer's needs, desires, demands, as well as their mindset and values.

Leverage project data

Six Sigma is a very heavy data-driven approach to project management, using the insights buried in numbers to reveal otherwise unforeseen or inexplicable areas of inefficiency. Always have a clear idea of what data you need, why, how you plan to collect it, and what metrics you are using to search for insights and measure success.

Reduce wasted resources 

Getting rid of inefficiencies like bottlenecks, wasted resources, or defective results is what Six Sigma is all about, and you need to keep such an inefficiency-seeking focus always in high gear. This is particularly key when talking about processes that can be done quicker, cheaper or more consistently. 

The stakeholder principle

Stakeholders mean a lot more than just shareholders, or workers, or end users. It’s all of the above and so much more. Throughout the process, you want to make sure all your stakeholders are keeping the ball rolling on whatever role they play, whether that means collaboration during brainstorming processes or regular consultation and feedback with the customer.

Stay ready for change

Change management is another thing that Six Sigma helps you do well. In principle, Six Sigma is not about one-time big revolutionary solutions, but rolling with the punches for continuous improvements. This means you have to stay flexible and agile according to new developments, and to not let your team get too off course with every little obstacle or setback.


Six Sigma advantages and disadvantages

Let’s talk about some of the pros and cons of the Six Sigma method.

Six Sigma benefits

Here are some advantages of Six Sigma:

  • Six Sigma standardization means everyone is on the same page at all times

  • You speed up the process of producing deliverables

  • You waste less money and cut costs by fixing problems and reducing defects

  • Anyone practicing Six Sigma and getting certified will have many career opportunities

  • It helps teams and managers work more closely together with higher levels of trust

Six Sigma drawbacks

Now for some Six Sigma disadvantages:

  • Too much administration and procedure can feel stifling to some

  • Putting customer satisfaction always blindly first might lead to project scope creep

  • There’s always the risk of creating data overload

  • Having to hire staff wit Six Sigma certification can be costly 


Our conclusion on Six Sigma methodologies

We trust this Six Sigma summary has been satisfactory, thorough, entertaining and illuminating. We’ve taken you through the early days of good ol’ Bill Smith over at Motorola, went into statistical analysis and standard deviations, to eventually sum up the pros and cons to Six Sigma overall.

When it comes to undertaking new initiatives, managing a project lifecycle, or focusing on continuously improving a product or your overall customer satisfaction levels, the Sigma Six methodology is highly applicable in many areas of business. And as a methodology, it can be implemented independently of whatever project management CRM you use. 

Good luck implementing Six Sigma now!


FAQs on the Six Sigma model

What do all Six Sigma process generally consist of?

The Six Sigma process generally consists of deciding if you are applying DMADV or DMAIC, and then going through the steps for each method. Six Sigma also comprises certified leadership roles in the form of colored belts. It also includes leveraging data and statistical analysis. 

Why is it called Six Sigma?

It is called Six Sigma based on the greek letter Sigma which is a term used in statistical quality control to describe things like standard deviations. In this case there are 6 deviations, meaning a deviation can occur to 3 degrees to either side of the standard.  

What is the difference between lean and Six Sigma?

Lean Six Sigma is not exactly the same as Six Sigma. With lean Six Sigma, there is more emphasis on process over product, as is the case with other lean and agile methods. Lean Six Sigma is close to the Kaizen method, and uses tools like value stream mapping.

What is another term for Six Sigma?

There is no singular other term that is an exact synonym for Six Sigma. Sometimes, you can replace calling your process Six Sigma by directly using the acronym DMAIC or DMADV, both of which describe the project process you’ll be using, including having design, measure and analyze stages.

Is Six Sigma still relevant?

Six Sigma is still very relevant to help manage improvement and streamline the overall business process, especially if you want to cut down on waste, avoid problems and reduce defects. Shrinking variables in your process and rationalizing deliverables has yet to go out of style.