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What is Lean Six Sigma?

25 Feb 2022
What is Lean Six Sigma?

n some business circles, there has been an ongoing debate comparing Lean principles with Six Sigma to determine the advantages of each system. However, combining both methodologies can lead to higher business efficiency and effectiveness. The Institute of Project Management provides a quick overview of both methods and the combination of Lean and Six Sigma.

what is lean six sigma

What is Lean?

Lean is a forward-thinking approach to value creation with fewer resources and waste. It focuses on continuous experimentation to achieve perfect value with zero waste. The main emphasis of Lean is on the customer, with two fundamental processes: thinking and practice. Thinking involves understanding customer values and problem-solving, while practice involves taking actions that directly and indirectly create value for the customer.

Organisations that adopt lean thinking and practice are highly adaptable to their environment and customer expectations. They strive to increase quality and flow while reducing time, effort, and cost. Gaining the skills to identify and eliminate waste and inefficiency in existing processes is crucial for organisational growth.

Brief History of Lean

The first person to integrate an entire production process was Henry Ford. In 1913, he created flow production by merging consistently interchangeable parts with standard work and moving conveyance. But this revolutionary break had one problem- the inability to provide variety. Later, in the 1930s, it occurred to Kiichiro Toyoda, Taiichi Ohno, and others at Toyota that a series of simple innovations might make it more possible to provide both continuity in process flow and a wide variety in product offerings. They revisited Ford's original thinking and invented the Toyota Production System. This system shifted the focus of the manufacturing engineer from individual machines and their utilisation to the product flow through the entire process.

What are the 5 Lean Principles?

Lean principles are simple to understand and quickly demonstrate results. There are five core principles of the Lean approach:

  1. Define value from the end customer's perspective.
  2. Identify all phases in the value stream and eliminate those that do not add value.
  3. Assemble value-creating activities in a precise order for smooth product flow.
  4. Allow customers to extract value from the next upstream operation.
  5. Repeat defining value, finding value streams, eliminating waste, and introducing flow and pull until perfect value is achieved.

Later on, these five principles were simplified to three: Purpose, Process, People.

What are the 8 Wastes of Lean? 

Originally, lean had only seven wastes that were developed by Taiichi Ohno, the Chief Engineer at Toyota. The 8th waste, unused talent, was added in later in the 1990s. This waste of non-utilised skills of workers was added when the Toyota Production System was adopted in the Western world. The acronym TIMWOOD then becameTIMWOODS:

  1. Transportation
  2. Inventory
  3. Motion
  4. Waiting
  5. Overproduction
  6. Over-Processing
  7. Defects
  8. Underutilised Skills
8 wastes of lean listed along with graphics

What is Six Sigma?

Six Sigma is a data-driven disciplined approach and technique used to identify and eliminate flaws or defects in any process, from manufacturing to transactional and from product to service.

The Six Sigma methodology's primary goal is to create a measurement-based strategy focusing on process improvement and variation reduction through data analysis and deploying Six Sigma quality improvement methodology across projects. Two Six Sigma sub-methodologies, DMAIC and DMADV, are used to accomplish this.

The first acronym stands for five words describing five consecutive phases of development - define, measure, analyse, design, and verify. The second one, DMAIC is also for the following steps: define, measure, analyse, improve and control.

These two methodologies differ in the last two phases. Improving rather than designing is the fourth step in an existing process. Likewise, verifying a process capability or pilot run in case of a new project gives way to a broader, long-term, and regularly performed control of already established products, services, or processes. The choice of which one will be used depends on the character of the project:

  • DMADV methodology is for projects which are focused on the creation of a new product, service, or process design
  • DMAIC methodology is for projects that aim for the improvement of an existing product, service, or processes.

Brief History of Six Sigma

Six Sigma was first introduced in the 1980s as a set of tools for process improvement. The term comes from the manufacturing process maturity rating, expressed by the Greek letter sigma. Motorola, an American communications company that developed six manufacturing goals, registered them as Six Sigma tools. Six Sigma is named after a statistical concept where a process only produces 3.4 defects per million opportunities (DPMO). Therefore, Six Sigma can also be viewed as a goal where methods consistently encounter fewer defects.

What are the 6 Sigma Principles? 

To help ensure the success of Six Sigma, keep these principles in mind:

  • Reducing variation of processes leading to stability in results
  • Clearly defined, measurable, analysed, and controllable characteristics of the business processes
  • A solid commitment to quality improvement shared by all levels of the given organisation
  • Clarity of focus on quantifiable profit
  • Emphasis on quality management and leadership in the organisation
  • A commitment to verifiable data and methods in the decision-making process

The goal of these principles can be described in terms of increase and reduction. Any project incorporating Six Sigma principles should experience increased profits and customer satisfaction, reducing costs, pollution, and process cycle time.

What is the Main Difference between Lean and Six Sigma? 

There are quite a few similarities between the two methodologies. For both, the value is defined by the customers through their direct experience. Data is collected to assess performance. Both approaches are widely used in different fields, far beyond the original manufacturing domain, and their implementation leads to waste and variation reduction.

On the other hand, the differences between Lean and Six Sigma are complementary. While Lean principles focus on reducing or eliminating waste, Six Sigma focuses on process variation. In both cases, the efficiency is improved. Where Six Sigma uses statistical analytical techniques, Lean relies on visual methods. Process changes are implemented through a revised value stream map in Lean processes, while Six Sigma implements changes by modifying setup procedures and measurement systems.

The Combination of Lean and Six Sigma 

lean six sigma combination graphics

Lean Six Sigma is kind of self-explanatory; It is a combination of the strategies of Lean and Six Sigma. It merges principles from both methodologies, creating a new one for Lean Six Sigma which is to help improve the efficiency and quality of the process.

Lean Six Sigma Principles 

Just like the two methodologies that are combined to make this one, Lean Six Sigma projects are also led by its principles. Those principles are enabling the deployment of Lean Six Sigma within the organisations. The Lean Six Sigma principles are the following:

1. Focus is on the customer 

At the center of any lean six sigma deployment should be aligning the bussiness processes with what a customer finds satisfactory. The goal of implementing any change you want should be to provide the customer with as many benefits as possible. That can be done by establishing what standard of quality the customer or market demands.

2. Define the problem and focus on solving it

When introducing new changes a lot of organisations make the mistake of doing too much simultaneously, losing the focus of the initial problem. Getting caught up with all the possibilities of improvement, they don't realise that what is actually needed is to do a real assessment of what matters the most to the customer and stakeholders. Gathering data that shows where a specific problem area lies is necessary because in order to sovle it, you have to define the problem first.

3. Eliminate inefficiencies

Once the problem is identified, it is time to look for ways to decrease defects. A lot of the time, this can lead to mistakes and waste. Differentiate between non-value added and value-added steps in the bussiness process. A lot of non-value adding steps lead to unnecessary mistakes and waste. By streamlining or removing theses functions you can achieve quality control and efficiency. Apply a philosophy of eliminating, simplifying, or automating processes and support them with consistent measurement of the outcomes so they can be further improved.

4. Communicate and align people

Consistent and efficient communication and Lean Six Sigma training are key to achieving success with any change, especially with the deployment of Lean Six Sigma. It is a requirement for Lean Six Sigma that all team members are acquainted with the Lean Six Sigma process, Lean Six Sigma tools and Lean Six Sigma techniques. They need to know the goals of the project and are informed about its progress. Because o all the changes happening during the implementation of new tools and techniques, management has to make sure they reduce the risk of projects failing and ensure the entire process is running smoothly.

5. Be flexible and adaptable

Identified inefficient processes must be refined or removed to facilitate change and drive improvement. Although this process can be challenging, it ultimately leads to a leaner, stronger, and more competitive company, a goal every business leader pursues. To enable change and improve business processes, organisational structures and management philosophies must align with new realities. As markets evolve rapidly, it is vital to anticipate future customer demands. Therefore, businesses must maintain dynamic capabilities within their processes and cultivate an organisational culture that is adaptable and agile.

Lean Six Sigma Belt Levels 

The Lean Six Sigma Belts are indicators of different stages of knowledge, skill and experience in a process of continuous improvement of practitioner's developmentBelt training has several different levels, labelled by the colors:

5 belt levels of lean sigma  shown in the pyramid structure

White Belt 

Lean Six Sigma White Belt holders possess a basic understanding of Lean Six Sigma principles. They can communicate potential issues and relevant points to individuals involved in process improvement projects. This level is typically assigned to everyone in the organisation who has received initial Lean Six Sigma training during its introduction. White Belts are crucial in ensuring widespread adoption of the impending changes.

Yellow Belt

Lean Six Sigma Yellow Belt individuals have a solid foundation in Lean Six Sigma methodologies. They contribute to process improvement projects and provide support to Green Belts. While Yellow Belts actively participate in Lean Six Sigma initiatives, they do not assume leadership roles.

Green Belt

Lean Six Sigma Green Belt individuals are like project managers, capable of managing process improvement projects. They drive the implementation of process improvement initiatives and possess the necessary expertise to implement Lean Six Sigma practices successfully. However, larger-scale projects often require the involvement of multiple Green Belts.

Black Belt

Lean Six Sigma Black Belts are pivotal in driving cross-functional process improvement projects. They possess extensive knowledge of Lean Six Sigma methodology and considerable experience in Lean Six Sigma and process improvement. Black Belts serve as mentors to the Belt levels below them, leveraging their expertise to guide and support project teams.

Master Black Belt

Master Black Belts are highly advanced and certified Lean Six Sigma practitioners. They play a strategic role in leading process improvement initiatives across the entire organisation. These individuals are instrumental in devising high-level strategies for streamlining operations, achieving cost savings, and ensuring sustainable improvements. Sigma Master Black Belt individuals oversee the application of Lean Six Sigma throughout the organisation and develop strategies for future initiatives.


Champions hold leadership positions within the organisation and wholeheartedly support and nurture a Lean Six Sigma culture. While executives can function as both Champions and Six Sigma practitioners, it is not a requirement for all Champions to assume this dual role. However, it is vital for all leadership within the organisation to champion Lean Six Sigma for its complete success actively.