What is Six Sigma

Guide: Six Sigma

Six Sigma is a data-driven methodology aimed at reducing defects and improving quality in processes by identifying and eliminating variability. It uses statistical tools and techniques for continuous improvement.
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Author: Daniel Croft

Daniel Croft is an experienced continuous improvement manager with a Lean Six Sigma Black Belt and a Bachelor's degree in Business Management. With more than ten years of experience applying his skills across various industries, Daniel specializes in optimizing processes and improving efficiency. His approach combines practical experience with a deep understanding of business fundamentals to drive meaningful change.

Guide: Six Sigma

Six Sigma is a method businesses use to improve their processes and reduce defects by being more consistent. It uses calculations such as standard deviation to find and fix the excessive variation in processes, with the aim of making products or services good enough to meet the customers needs. This guide will help you understand the basic ideas behind Six Sigma, how it works, why it’s helpful, and some important things to know about it.

What is Six Sigma?

“Six Sigma” is a term that comes from a mathematical idea used in manufacturing. When a production process is Six Sigma also known as 6 standard deviations away from the specification limits where problems and defects are produced, it means it is a very capable process and only produces up 3.4 defects out of a million opportunities. The goal of Six Sigma is not just to make things better in terms of quality but also to make sure they’re done more smoothly and work better by making less variation in how things are done.

Imagine you’re trying to hit a bullseye with a dart. Six Sigma is like being able to hit near the bullseye almost every single time because you’ve figured out all the little things that could go wrong (like the wind, the weight of the dart, or how you throw it) and you’ve fixed them. So, you’re not just good at throwing darts by chance; you’re good because you’ve made a science out of it. That’s what Six Sigma does for businesses – it helps them hit their quality targets over and over by finding and fixing problems.


The use of Six Sigma is applicable across a range of industries beyond just manufacturing. Industries such as defence, hospitals, and aerospace are particularly keen on adopting Six Sigma principles. In defence, the focus is on minimizing defects in equipment and systems crucial for national security, demanding high reliability under extreme conditions. Hospitals and healthcare systems utilize Six Sigma to enhance patient care by reducing medical errors, improving service efficiency, and ensuring patient safety, directly impacting health outcomes.

The aerospace industry, where the cost of failure is exceptionally high, applies Six Sigma to ensure the utmost precision in manufacturing, system reliability, and compliance with stringent regulatory standards. Across these sectors, Six Sigma is not just a set of tools but a fundamental approach to achieving excellence, operational efficiency, and a culture of continuous improvement, demonstrating a universal commitment to setting and surpassing high standards of quality and performance.

The Six Sigma Methodologies

Six Sigma uses two main strategies for managing the improvement process called DMAIC and DMADV to help businesses do things better, whether they’re trying to improve what they already do or create something new.



DMAIC is a five-step method used to make existing processes better. Here’s what each step means in simple terms:

  • Define: First, figure out what the problem is or what you want to achieve with a process that’s not doing as well as it could.
  • Measure: Next, gather information about the current process. This helps you see how things are going right now, so you know what needs changing.
  • Analyze: Look closely at the information you collected to find out exactly why things are going wrong.
  • Improve: Once you know why problems are happening, you can start fixing them. This step is all about making changes to get rid of these problems.
  • Control: Finally, keep an eye on the process after making changes to make sure the improvements last and the process doesn’t start having problems again.

the five phases of DMAIC, Define, Measure, Analyse, Improve and Control

Think of DMAIC like fixing a leaky tap. First, you figure out (define) that the tap is leaking. Then, you watch (measure) how much water is dripping to understand the problem’s size. Next, you look (analyze) under the sink to find out why it’s leaking (maybe a worn-out washer). Once you know the cause, you fix (improve) it by replacing the washer. Lastly, you keep checking (control) the tap for a while to make sure it doesn’t start leaking again.


DMADV is another five-step method, but this one is for creating new processes or products. Here’s a breakdown of the steps:

  • Define: Start by deciding what the goals are for the new product or process and what customers need.
  • Measure: Identify the important things that will make the product or process good quality (CTQs), what it should be able to do, how the process should work, and any potential risks.
  • Analyze: Think about different ways to meet those goals and needs, and design a rough version of the best one.
  • Design: Develop the detailed version of the product or process you chose in the last step.
  • Verify: Check that your design works the way it should. You might do some tests or try it out in a small way before making it the standard way of doing things and giving it to the people who will use it.


Using DMADV is like planning a garden. You decide (define) what you want from the garden (like vegetables or flowers), figure out (measure) what plants will grow well in your space, and what tools you’ll need. Then, you think about (analyze) where everything should go for the best results. After that, you draw a garden map (design) with all your plants and paths laid out. Finally, you plant a few things as a test (verify) to see if they grow well before planting the whole garden.

Key Concepts of Six Sigma

In Six Sigma, there are some important ideas and tools that help make processes better by finding and fixing problems. Let’s break these down into simpler terms:

Process Mapping

Process mapping is visualising the process. Imagine drawing a map that shows every step of how something gets done, from start to finish. This map helps everyone see exactly how a task or process works, making it easier to spot where things might be going wrong or could be done better.

Basic flow chart or Process map

Detailed sub process map

SIPOC Diagrams

SIPOC stands for Suppliers, Inputs, Process, Outputs, and Customers. It’s like a snapshot that shows the starting point (where and what you get from suppliers), what you do with what you get (the inputs and process), what you end up with (the outputs), and who ends up with it (the customers). It’s a tool to quickly see the big picture of a process and understand its main parts.

Example of complete SIPOC

Control Charts

Think of control charts like tracking charts that help you watch how something changes over time. By keeping an eye on this chart, you can see if the way you’re doing things is staying on track or starting to go off course, sort of like watching the speedometer while driving to make sure you’re not going too fast or too slow.

Control Chart - LearnleanSigma

Root Cause Analysis

Root Cause Analysis is like detective work to figure out the real reason something went wrong, not just dealing with the symptoms. For example, if a plant is dying, instead of just giving it more water, you’d figure out if the problem is actually something else, like too much sun or poor soil. Finding the root cause helps you fix the problem for good.

Example Fishbone Diagram

Statistical Analysis

This uses math to make sense of information by looking for patterns, differences, or changes over time. It’s like when you track scores of your favorite sport to predict which team might win the next game. In Six Sigma, statistical analysis helps understand data from processes to make better decisions about how to improve them.

All these tools and concepts are part of Six Sigma’s toolkit to help businesses do things better, by making sure every part of a process is as good as it can be. They turn guesswork into a science, making improvements based on real information and analysis.

Benefits of Six Sigma

When a company decides to use Six Sigma, it can expect a lot of benefits. Let’s break down these benefits and look at how a company starts using Six Sigma.

Benefits of Six Sigma

  • Improved Quality: Just like making fewer mistakes when you’re doing something important, Six Sigma helps companies make fewer mistakes in their products or services. This means what they sell or provide gets better and has fewer problems.
  • Increased Efficiency: Imagine finding a faster way to clean your room that does an even better job than before. That’s what Six Sigma does for businesses – it finds smarter, quicker ways to do things, which saves time and money.
  • Customer Satisfaction: When the stuff you buy works great and doesn’t break, you’re happy, right? Six Sigma aims to make customers happy like this by making products more reliable, which means people will keep coming back.
  • Employee Engagement: Six Sigma gets everyone involved in fixing problems, kind of like being part of a detective team at work. This makes jobs more interesting and can make people want to stay with their employer longer.
  • Financial Performance: When you make better products faster and customers love them, your company spends less money on fixing mistakes and makes more money from happy customers. It’s like getting better grades with less study time, which is great for any business.

Implementing Six Sigma

Imagine you’re part of a sports team, but instead of playing soccer or basketball, your goal is to make your company as good as it can be. This is what starting Six Sigma at a company is like. Here’s how it works, broken down into simpler terms:

  1. The Coach’s Decision: The first step is like the coach (the company’s leaders) deciding they want to win the championship (improve the company). They need to be really into this idea, ready to support the team, and lead by example.

  2. Picking the Team: Next, the coach picks players with special roles. In Six Sigma, these are the Green Belts, Black Belts, and Master Black Belts. Each of these “players” gets special training:

    • Green Belts are like the players who are learning the game. They work on projects part-time while doing their regular jobs.
    • Black Belts are more like the star players who spend all their time working on making things better, leading projects, and helping Green Belts.
    • Master Black Belts are like the top players or even assistant coaches. They’re experts who guide Black Belts and Green Belts, oversee multiple projects, and help develop strategies.
  3. Training Camp: Before the season starts (the projects begin), these players go through training camp (Six Sigma training). Here, they learn all the moves (Six Sigma methodologies) they need to play the game well. They practice spotting where the team is losing points (identifying problems), figuring out why they’re not scoring (analyzing the causes of the problems), and working out new plays to win (finding solutions to improve the process).

  4. Game Time: With training done, it’s time to play the game (start the projects). The team works together, using what they’ve learned to score points (solve problems). They keep an eye on the scoreboard (monitor progress with tools like control charts) to make sure they’re winning (improving the process).

  5. Winning the Championship: The ultimate goal is to win the championship (achieve significant improvements in the company). This doesn’t just mean a trophy (though recognition is part of it). It means happier customers, less money wasted, happier workers, and a better company overall.

Just like in sports, not every play (project) will be a win, but the team learns from each game. Over time, with practice and good coaching, the team gets better and better, making the company a real champion in its field.


Six Sigma is a powerful methodology for driving process improvement and quality enhancement in any organization. By understanding and applying its principles, methodologies, and tools, companies can achieve substantial improvements in performance, customer satisfaction, and financial results. Whether addressing existing processes through DMAIC or developing new processes with DMADV, Six Sigma offers a structured approach to achieving excellence in operations and product quality.


A: Six Sigma is a set of techniques and tools for process improvement. It aims to reduce the number of defects in a process, enhance quality, and improve efficiency by systematically removing variables and errors.

A: Almost any organization can benefit from Six Sigma, regardless of its size or industry. It’s particularly useful for manufacturing, healthcare, finance, and technology sectors, but any organization looking to improve processes, reduce waste, and enhance customer satisfaction can find value in Six Sigma.

A: The main levels of Six Sigma certification include Yellow Belt, Green Belt, Black Belt, and Master Black Belt. Each level represents a deeper knowledge of Six Sigma methodologies and a greater ability to lead and implement projects.

A: While Six Sigma focuses on reducing defects and improving process quality by addressing variability, Lean emphasizes eliminating waste and improving workflow efficiency. Lean Six Sigma combines the two methodologies to maximize process efficiency and quality.

A: Six Sigma can be applied to businesses of all sizes. While large corporations may have more resources to implement Six Sigma, small businesses can also adopt its principles to streamline operations, improve quality, and enhance customer satisfaction. The flexibility of Six Sigma allows it to be scaled according to the specific needs and capabilities of any organization.


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Daniel Croft

Daniel Croft is a seasoned continuous improvement manager with a Black Belt in Lean Six Sigma. With over 10 years of real-world application experience across diverse sectors, Daniel has a passion for optimizing processes and fostering a culture of efficiency. He's not just a practitioner but also an avid learner, constantly seeking to expand his knowledge. Outside of his professional life, Daniel has a keen Investing, statistics and knowledge-sharing, which led him to create the website www.learnleansigma.com, a platform dedicated to Lean Six Sigma and process improvement insights.

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