What is Lean Six Sigma: A Closer Look at How and Why it Works

Lean Six Sigma (LSS) has been around for over three decades and is being used by more than two million companies worldwide to improve the quality of their processes. And yet, many of the principles behind Lean Six Sigma still seem to be misunderstood, LSS is much more than just a quick fix.

 According to the American Society for Quality (ASQ), Lean Six Sigma is a fact-based, data-driven philosophy of improvement that values defect prevention over defect detection. It drives customer satisfaction and bottom-line results by reducing variation, waste, and cycle time, while promoting the use of work standardization and flow, thereby creating a competitive advantage. (see ASQ

It is a process that combines statistical methods with business strategies in order to improve business performance, consequently, achieving operational excellence. 

LSS has been used in a wide variety of industries, including automotive, food manufacturing, pharmaceuticals, insurance, education, energy and more. 

But really, what is Lean Six Sigma, how does it work, and what exactly do we need to know about it in order to implement it effectively in our business? 

In this article, we will take a closer look at what is Lean Six Sigma, how and why it works for a number of Fortune 500 companies operating in every industry around the globe.

How did Lean Six Sigma Start

Lean Six Sigma started coming together in the late 1900’s, but the word Six Sigma originated back in the early 1800s. 

The term Sigma was once used as a measurement concept founded by Carl Frederick Gauss. Gauss introduced the concept of the normal curve metric. 

Six Sigma focused on improving quality whereas Lean focused on removing excess waste.

Six Sigma was coined in 1988 by Bill Smith who worked as an engineer for Motorola. He brought forth the theory of latent defect and helped Motorola prove that eliminating variations helps eliminate the waste of defects which in turn could save the company millions of dollars. 

Due to this change that Motorola made, it was selected as the first large manufacturing company to win the Malcolm Baldrige National Quality Award. Six Sigma is now a trademark of Motorola.

The concept of Lean was first developed in 1799 when Eli Whitney established the premise of making production work faster for what little money was available and making sure nothing was being wasted. He is the originator of interchangeable parts.  

Henry Ford took this concept to his manufacturing plant in the 1910’s, wanting to produce as many vehicles as possible without wasting time or money. 

Toyota followed right behind realizing that making the product that the buyer wanted, at the time it was needed was the way to go. Toyota also believed that the best productivity was using employees to the best of their abilities. 

Lean Six Sigma has now been successfully embraced globally in many diverse industries and corporations.

What is Lean Six Sigma

Lean Six Sigma is an amalgam of the practices of both Lean methodology and Six Sigma, bringing together the concepts and methodologies from each of these disciplines to create a powerful combination.

 When you apply Lean and Six Sigma to the same process, you create a more efficient and effective manufacturing system, one that can produce the same or even better quality products or services at a lower cost than was previously possible.

What is Lean

Lean started as a technique to reduce waste primarily at the factory floor. Soon, it was being used to streamline transactional office and service processes. 

It has now developed into a means for improving more demanding aspects of knowledge work, including: engineering, product development, software development, and medical advancement. 

The key concepts of Lean have also been applied to highly complex projects, leading to developments, including: Lean Project Management, Lean Construction, and Lean Health Care.

Lean refers to maximizing customer value and minimizing waste; creating more value for customers with less wasted resources. 

Lean is focused on the reduction of hidden waste – the elimination of non-value-added steps, viz., Defects & Rework, Overproduction, Waiting & Delays, Not Using People Well, Transportation, Inventory, Motion in Excess, and Excess Processing. (DOWNTIME)

Lean aims to make the process effective (Simplify the Process).

What is Six Sigma


Six Sigma is a metric based on the statistical measure called standard deviation: 

For businesses, it aims for world-class quality, and customer-focused processes and services that are Better, Faster, Lower Cost, and Safer than our competition. 

Six Sigma is a data-driven methodology, a statistical analysis tool, and a management quality system designed to streamline business processes by eliminating defects. 

Statistically, it means driving towards six standard deviations from the process mean to the nearest specification limit.  This means transforming a process whose quality level yields a virtually zero-defect rate of 3.4 defects per million (dpm).

Six Sigma is the ongoing effort to continually reduce process and product variation through a defined project approach. 

Six Sigma focuses on the relentless and ruthless pursuit of variance reduction.  It aims to make the process efficient (Perfecting the Process).

What is Lean Six Sigma


Lean Six Sigma is a system focused on meeting or exceeding customer requirements using facts, reliable data and applying the rigor of the DMAIC Process = Define, Measure, Analyze, Improve & Control. It involves using the right tools at the right time to answer the right questions. 

LSS is not a quality control program that focuses on fixing mistakes.  

Six Sigma prevents mistakes or defects from ever happening. 

Lean Six Sigma propels businesses to transform themselves through breakthrough improvements and continuous improvement to be competitive and grow their business. 

If we do this correctly, our business will grow, all employees will be involved and grow in knowledge and skills.  Six Sigma improvements enhance employment security. 

To successfully practice LSS, we must have the commitment, leadership, and willingness to support this change.

What are the Benefits of Using Lean Six Sigma

Lean Six Sigma creates business value to organizations by increasing the value-add of its goods and services to their customers, reducing operational costs, increasing efficiency and productivity (removing waste in its processes), improving quality, and meeting its business goals and objectives.

In today’s competitive business environment, success depends on constantly finding ways to work smarter, faster and better. 

A major, company-wide commitment to LSS can drive dramatic improvements in every aspect of a business. 

By integrating the LSS tools and processes, businesses can create a powerful program for improving quality, efficiency and speed throughout the organization. 

Lean Six Sigma delivers results through a thorough understanding of the value stream and determining the input variables that deliver the desired outputs by eliminating waste and reducing variation.

Is Lean Six Sigma Applicable to all Organizations?

Lean Six Sigma is a management tool based on the premise that continuous improvement and optimization can be achieved through the application of statistical analysis tools and other methodologies such as Kaizen and PDCA (Plan Do Check Act). 

In Lean Six Sigma, the success of an organization is determined by the ability to eliminate waste from its operations. This waste is a result of human error and other unnecessary activities. 

LSS has been adopted by a wide range of industries including manufacturing, transportation, financial services, healthcare, and telecommunications. 

Further,  LSS can be applied to all areas of a company—including customer service, logistics, product development, marketing, and finance.

What are the Lean Six Sigma Principles

Lean Six Sigma is a powerful, proven method of improving business efficiency and effectiveness. 

In a nutshell, these are the key principles of Lean Six Sigma Business Transformation:

  • Specify VALUE in the eyes of the customer
  • Identify the VALUE STREAM; eliminate WASTE and VARIATION
  • Make value FLOW at the PULL of the customer
  • Involve, Align & EMPOWER Employees


What are the Lean Six Sigma Tools and Techniques

Lean Six Sigma involves a structured set of tools and techniques used to eliminate waste from the business process. LSS also looks at how a company’s processes are currently operating and determines whether the processes can be improved to make the company more efficient.

The Lean Tools

Value Stream Mapping (VSM)

VSM is a method of presenting processes in the form of a one-page picture. It includes all the processes that occur in a company, from the time order is placed till it is delivered to the customer. 

VSM identifies all the value adding and non-value adding processes in this picture. All the non-value adding processes (wastes) can be eliminated by studying the map. 

Once the Value Stream Map is created, it is used as a basis for all further improvements and reduction in waste.

Theory of Constraints (TOC)

TOC is a methodology for identifying the most important limiting factor (i.e., constraint) that stands in the way of achieving a goal and then systematically improving that constraint until it is no longer the limiting factor. 

This constraint is also more commonly referred to as a bottleneck. A constraint is anything in an organization that limits it from moving toward or achieving its goal. 

There are two basic types of constraints: physical constraints and non-physical constraints. 

A physical constraint is something like the physical capacity of a machine. 

A non-physical constraint might be something like demand for a product, a corporate procedure, or an individual’s paradigm for looking at the world.

Physical Flow

A Physical Flow shows the path followed by materials, people or information as they move across a field or facility in completing a process. 

It also helps identify wasteful activities, and familiarizes everyone with the process as it actually takes place.

Jidoka & Mistake Proofing

Jidoka represents an attitude towards problems in the workplace: surfacing problems and addressing them head-on, rather than accepting them and devising workarounds. 

Moreover, Mistake Proofing (Poka-Yoke) is a systematic approach to preventing and detecting errors or mistakes at their source so they cannot be passed to the next step in the process or to the external customer.


5S is a structured method for creating and maintaining a clean, organized and visual workplace. It is not enough to exhort personnel to keep the workplace clean and organized. 

A method and a routine have to be established.

  1. Sort: When in doubt, take it out.
  2. Set in Order: A place for everything, everything in its place.
  3. Shine: Cleaning and inspecting.
  4. Standardize: Who, when and how for the first 3S.
  5. Sustain: Management commitment and presence.

Visual Workplace

In the Lean environment, a Visual Workplace is (i) Transparent: even a stranger can easily understand, without asking, the flow of work and what is currently going on; (ii) Supportive: workers can find what they need when they need it: forms, tools, information, materials and people. and (iii) Self-directed: workers know what needs to be done next, and how to do it, without detailed directions from supervisors or computer systems.

Kanban Cards

Kanban Cards are “mini work orders” that request that an item be produced, moved, or purchased within your supply chain. 

They usually include details such as: (i) What is being requested, how many and where they can be found; (ii) Where it must go; and (iii) Additional useful information (a picture of the item, supplier’s fax number, etc.) Kanbans can be designed so they can be easily faxed to an external provider or a faraway facility. 

Kanban is a way to manage your workflow to help you visualize your work, maximize efficiency and be agile. 

Kanban (Japanese term) literally means billboard or signboard. 

Just in Time/Single Piece or Batch Flow

In the ideal timeline the items would “flow” uninterrupted from one operation to the next, without delay. 

As an item finishes being processed in one activity, it immediately starts being worked on in the next one. This demands zero inventory in between process steps. Inventory creates delays and stalls the flow. 

Items may flow either one by one (one-piece flow) or more generally according to Transfer Batch = Processing Batch.

Since we can adjust our process to work at different rates, we should operate at the rate that allows production to meet demand; no more and no less. 

Takt Time defines this pace, the one at which production meets demand. It sets the pace for the whole operation.

Quick Changeover 

Quick Changeover results in more than just reduced time; it also enables more frequent events and enhances standardization and safety. 

In manufacturing, Changeover (or Setup) is the process of switching from producing one model to another in a machine or series of machines. 

In general, a Changeover occurs whenever an activity interrupts production, e.g., preventive maintenance, equipment repair, compliance testing, etc. 

To measure Changeover Time: Time the process from the last good part produced with the old setup to the first good part produced with the new one. “Last good item to first good item”.

Total Productive Maintenance

Womack and Jones in “Lean Thinking” (See Lean Thinking (1996), Simon and Schuster) expressed that it is imperative to “Ensure that every machine in a production process is always able to perform its required tasks, so that production is never disrupted.” This is Total Productive Maintenance. 

Further, Seiichi Nakajima in “Introduction to TPM” (See Introduction to TPM: Total Productive Maintenance (1988), Productivity Press) mentioned that TPM can be achieved through: Zero downtime, Zero defects, Zero accidents, and Zero pollution.


Kaizen is from the Japanese word kai, meaning change, and zen, meaning better: change for the better. It refers to continuously improving in the way that work is conducted, progressively reducing waste and increasing added value.

 Consequently, a Kaizen Event is an intensive team activity devoted to workplace and process improvement. Also known as: Kaizen Blitz, Kaizen Workshop, Rapid Improvement Workshop, Lean Event, etc.

The Six Sigma Techniques


The IPO diagram is the starting point of an improvement project. 

This is a high-level process that is followed by flow diagrams, process mapping and eventually Design of Experiments (DOE) to fully understand the process and all related sub processes. 

It is a simple tool to define a process and focus on the key variables.

 It is critical to understand the IPO process and relate how inputs are linked to outputs.

Cause & Effect Diagram

A Cause and Effect Diagram is a visual tool used to logically organize possible causes for a specific problem or effect by graphically displaying them in increasing detail, suggesting causal relationships among theories.

 It is also known as the Fishbone diagrams or Ishikawa Diagram named after Kaoru Ishikawa who created the diagram. 

Pareto Chart

Pareto Chart is a Bar Chart for Attribute or Categorical Data that is presented in Descending Order of Frequency or Monetary Loss. Used to separate the vital few from the trivial many, answering what key inputs effect the performance measures. 

Pareto charts are extremely useful for analyzing what problems need attention first because the taller bars on the chart, which represent frequency, clearly illustrate which variables have the greatest cumulative effect on a given system. 

The Pareto Chart provides a graphic depiction of the Pareto principle, a theory maintaining that 80% of the output in a given situation or system is produced by 20% of the input.

Statistical Testing

In Statistical Testing, a population data set contains all members of a specified group (the entire list of possible values) while a sample is a part of, or a subset of a population. Here is a list of the common Statistical Parameters used in Six Sigma:

Design of Experiments (DOE)

DOE is a structured means of experimentation which results in an efficient identification and prioritization of input factors that affect process outputs. This information can then be used to select optimum solutions. 

DOE is the process of planning experiments so that appropriate data can be analyzed by statistical methods that results in valid, objective, and meaningful conclusions from the data.  It involves two aspects: Design and Statistical Analysis.

Measurement System Analysis (MSA)

MSA is defined as an experimental and mathematical method of determining the amount of variation that exists within a measurement process. 

Variation in the measurement process can directly contribute to the overall process variability. 

MSA is used to certify the measurement system for use by evaluating the system’s accuracy, precision and stability (Quality-One International, https://quality-one.com/msa/).

Failure Modes & Effects Analysis (FMEA)

An FMEA is a structured and systematic method for prioritizing potential failure modes. 

The tool looks for three aspects of each failure mode: (i) Severity of the failure; (ii) Likelihood the failure will occur; and (iii) Likelihood the failure will escape detection with the current control system. An FMEA can evaluate: (i) Current processes; (ii) Designs of products; and (iii) Defect analysis.

5 Whys

5-Whys is a simple approach for exploring root causes and instilling a “Fix the Problem” culture at all levels. 

Straightforward problem-solving solution derived from answers which are arrived through team discussion rather than formal analysis and experimentation. 

Ask the question “Why” five times to get to the root cause of the problem.

Standard Operating Procedures (SOPs)

SOP must be developed with the entire team and must get agreement on each point. This is used to eliminate noise variables and reduce variation in the process. 

Variance reduction is the key to process optimization and reduction in the Cost of Poor Quality.

What are the Five Phases of Lean Six Sigma – DMAIC

The Define Phase 

The Define in the DMAIC process is about selecting high payback projects and identifying the underlying metric(s) that will measure project success. 

Lean Six Sigma projects create incremental work, and leadership teams must be convinced that the payback will be worth the effort. 

Without senior leadership oversight and support, project leaders will typically be overwhelmed with resistance from the organization and will make little progress. This situation can be prevented if senior leaders oversee the Define process and schedule project reviews at regular intervals. 

Outlined below is a brief overview of the most common tools used in this phase. The key deliverable of the define stage is an agreed Project Charter.

The Measure Phase

The Measure in DMAIC is about understanding the current process, how the process is measured, and its baseline (historical or pre-Lean Six Sigma) performance. 

An important aspect of the Measure phase is verifying the reliability of the data.  

Outlined below is a brief overview of the most common tools used in this phase.

The Analyze Phase

This phase starts with team input regarding potential causes and uses statistical methods to isolate the top issues to be discussed.  

Oftentimes, there is one primary cause that is driving most of the unwanted variation and controlling or eliminating this cause is all that is needed. 

Outlined below is a brief overview of the most common tools used in this phase.

The Improve Phase

The Improve phase is about redesigning the process to achieve improved capability. This involves brainstorming potential solutions, selection solutions to test and evaluating the results of the implemented solutions. 

Outlined below is a brief overview of the most common tools used in this phase.

The Control Phase

The Control Phase of the Lean Six Sigma DMAIC Process consists of executing the Control Plan and finalizing the project documentation. 

Monitor post implementation process performance to ensure expected improvement in the project has occurred. Ensure ongoing process monitoring system is in place. Communicate the Business Results and sign off to close the Lean Six Sigma Project. 

Outlined below is a brief overview of the most common tools used in this phase.

How does Lean Six Sigma Work

Lean Six Sigma is often used by companies to continuously improve their processes. By eliminating poor performing processes, companies can improve customer experience, which in turn drives customer satisfaction and repeat business.

Lean Six Sigma was created by Motorola when they were having problems with their production processes. 

They started looking at all the problems in their manufacturing processes and thought of ways on how to minimize them. They also looked at how they could make their products better and faster. 

Then, they decided to use Six Sigma. 

They started with questions and used various data gathering and analysis tools to find answers. They learned what was working and what wasn’t working for their customers. 

From this data, they devised a plan for process improvement and came up with solutions that were specific for their company. 

Once they had a plan, they implemented it, measured the improvement they have achieved with the goal of continuously improving these processes. 

They continue to collect data to make sure that they were on track, and used these to make better decisions in the future.

How to Get Started with Lean Six Sigma

Before you can get started with any type of improvement initiative, you need to understand the basics. Lean Six Sigma is a system for continuous improvement in operations. 

LSS is the world’s first methodology to systematically eliminate waste from organizations, and one of the most powerful tools in business. 

LSS can be applied to any industry, to any process, and at every scale. It’s not just for Fortune 500 companies, but can also be applied to a local restaurant or small business. 

Discover a detailed list of Lean Six Sigma project examples and ideas here to help you get started.  

Moreover, to get started with LSS, you need to have a positive mindset and be willing to do whatever it takes to succeed, besides, LSS is not just a method of improving business processes, but a way of life. 

If you are interested in this type of improvement methodology, you should get started right away and aim for your Lean Six Sigma Certification.

Finding a Course that Fits Your Schedule and Learning Style

So, you want to have a Belt Certification in Lean Six Sigma, be a Sigma Yellow Belt, Sigma Green Belt, Sigma Black Belt, or a Sigma Master Black Belt, even. You are not alone. 

Many individuals typically think that taking a Lean Six Sigma course and achieving their Sigma Belts is out of reach. 

This is because (a) there aren’t any classes offered in their area; (b) they don’t have the time to take online classes; (c) they don’t have the time to travel to a classroom location; or (d) they have other priorities in life that prevent them from taking a course. There are alternatives to traditional classes, though.

At Variance Reduction International, Inc. (VRI), we offer fully customizable Lean and Six Sigma Training Courses for Yellow Belt, Green Belt, and Black Belt, to fit any industry or schedule.

Week #1 – Green Belts (GBs) and Black Belts (BBs)

  • Learn the LS Basics: How to thoroughly scope and baseline a process.
  • Focus areas: Define, Measure

White Belt Training – After Week #1, GBs/BBs should determine who will be on their team, those people should be trained in basic LS tools to help deploy projects.

  • Focus areas: Basic DMAIC overview

Week #2 – GBs and BBs

  • Find and reduce waste, and variance in processes. Determine root cause.
  • Measure process shifts and develop control plans to hold gains. Determine cost benefit of changes made.
  • Focus areas: Analyze, Improve and Control

Week #3 – BBs

  • Learn more advanced methods to make improvements with the LS tools.
  • Focus areas: Analyze, Improve and Control

Week #4 – BBs

  • Learn how to optimize processes with the use of multiple regression analysis – DOE.
  • Focus areas: Analyze, Improve and Control

Learn and master the Lean Six Sigma methodology and get your Lean Six Sigma Certification with us now!

Maria Milo is a Continuous Improvement Teacher and Lean Six Sigma Master Black Belt.She is on a mission to teach people how to apply continuous improvement tools, methods and the thought process in important aspects of life; business, career, and self. Maria has 25+ years of career experience and is President of Variance Reduction International, Inc (VRI). Her experience has taught her that when people are able to continuously improve themselves and their environment, they can achieve great things and lead happier lives.
Maria Milo
Maria Milo