Difference Between Six Sigma and Lean

Edited by Diffzy | Updated on: April 30, 2023


Difference Between Six Sigma and Lean

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Our daily tasks can eventually get boring. Being locked up in our houses during the pandemic has made everyone aware of this realization. It is hard to stay upbeat at all times. To remain motivated, waking up every single day with the basic goal of survival in the mind, eventually gets exhausting. It does not matter what you tell yourself at night, the struggle to get out of bed every morning remains the same. It is the same for all and the same for every day. It is nothing to be ashamed of. All of us are in the same boat. True, some of us are better at dealing with what the day has in store for us but that does not mean that the rest of us are slobs for striving hard to drag ourselves out of bed.

Yes, every task is hard even if it looks deceptively simple. Accomplishing any such task mostly requires will and to achieve that will, we need a spark of motivation. That spark is ignited by all that we are, all that we see – our experiences, circumstances, and surroundings. You read that right. Our surroundings matter very much. Structure and organization help make any process easier and doable.

Six Sigma vs. Lean

In the manufacturing world, achieving targets takes precedence over most other objectives. It is of utmost importance to have an organized plan with minimal distractions and faults to achieve targets. It serves well to remove unnecessary hindrances so that the efficiency of the process can be improved. Six Sigma and lean methodologies are two such ways that help boost the management process. Six sigma removes unessential defects in the process, while lean methodology focuses on removing useless steps in the management process. Let us see how they further differ from each other.

Differences Between Six Sigma and Lean in a Tabular Form

Purpose Six Sigma has the purpose of improving the quality and efficiency of the business process by eliminating wasteful practices. Lean has the purpose of streamlining the production process by eliminating wasteful practices and ensuring only essential steps are taken.
Origin Six Sigma was put forth by Bill Smith and Mikel J. Harry. They worked for the American company – Motorola. The Lean manufacturing process was an idea put forth by Henry Ford. It was later implemented by Toyota.
Year of origin Six Sigma was introduced in 1986. The idea was developed by Henry Ford at the start of the 20th century. The term ‘Lean manufacturing’ was coined in 1991.
Etymology Six Sigma uses the Greek symbol sigma to denote the standard deviation from the mean in a normal curve. Three sigmas below the mean and three sigmas above the mean constitute minimal error. The state of Six Sigmas is when there are 3.4 defects for every one million opportunities. The Lean manufacturing process is called Lean because it serves to trim down the excessive activities and keep only essential activities for the working of the manufacturing process.
Focus To eliminate wastes that hinder the progress of the manufacturing process. To eliminate waste and improve the process of manufacture.
Processes Six Sigma is a program or a process that minimizes waste. Lean is more of a philosophy and modulates the process of manufacturing to improve efficiency.
Goal Six Sigma works to achieve near-perfect results. Lean works to reduce cycle time and eliminate waste.
Consistency Six Sigma is a process that strives to get consistent results. The Lean process looks to maximize the flow of the work.

What is Six Sigma?

Six Sigma is a method in data approach that improves the process of manufacturing by getting rid of any defects that could pose hurdles for the same. It was developed by Bill Smith and Mikel J. Harry, working at the American company Motorola in the year 1986. Their intention for Six Sigma was very specific – to minimize defects in any process of manufacturing. For this, they employed two approaches –

  1. DMAIC – Define, Measure, Analyse, Improve and Control.
  2. DMADV – Define, Measure, Analyse, Design and Verify.

Thus, Six Sigma, quests to reduce errors. The origin of Six Sigma is in statistics. In the normal bell curve, the Greek symbol sigma denoted the deviation from the mean. Therefore, three deviations above the mean and three deviations below the mean constitute the Six Sigma model. Any process that has deviations within Six Sigmas is known to have a defect rate that is ‘extremely low’.

Six Sigma works to benefit the customer greatly. to do this, it first identifies the errors and then aims to formulate an effective solution. It has the following five principles:

  1. Focusing on the customer: As mentioned above, Six Sigma is customer-focused. For this reason, the customer is analyzed and their preferences and problems are given precedence. The needs, motivations and benefits are researched so that sales achieved are high and customer satisfaction is maximum.
  2. Measuring the value stream and discovering problems: To understand the value of the business, all the data is gathered and an appropriate charting is done to figure out what the defects are and how to make better the stance of the company.
  3. Eliminating the waste: Once the problems or defects are identified, they are eliminated. All the activities that do not add value to the customer’s needs or prolong the process unnecessarily are gotten rid of. Changes to make the process smooth with minimal friction are made. If valuing does not reveal defects, tools are employed to find these errors and outliers.
  4. Maintenance: It is important to include all the stakeholders in the discussion and make them aware of the problems. The team is made to dissect the problem and offer suggestions to enhance the process. Every member’s experience and insight help tackle the problems better and give innovative solutions to an otherwise complex problem.
  5. Ensuring a responsive ecosystem: Six Sigma enforces transformation and change. To be able to accomplish the highest level of excellence, one has to be flexible and dynamic. Ergo, Six Sigma ensures that the company remains open to change and makes the changes necessary to ascertain customer satisfaction.

Six Sigma utilizes multiple techniques and data analysis tools. Some of them are as follows:

  • Brainstorming: It is bouncing off ideas and generating creative solutions to a problem via group discussions.
  • The Five Whys: In a group discussion, to understand the root cause of the problem, the question ‘why’ is asked till the cause is discovered. The rule of thumb is to question five times, but it could be greater than that or lesser depending on the problem.
  • Using the voice of the customer: It is using the ‘voice’ of the customer or the customer feedback to figure out how to best satisfy the customer.
  • The 5S system: This is a Japanese technique. It uses the five steps – Seiri or to sort; Seiton or to set in order; Seiso or to shine; Seiketsu or to standardize; Shitsuke or to sustain.
  • Kaizen technique: This is the process of continuous improvement. There is constant monitoring, identifying errors and improvements made to reduce errors.
  • Poka-yoke: Another Japanese technique that serves to make the process ‘mistake-proof’. It is spotting and removing human errors in the manufacturing process.

The data analysis tools used are – cause and effect analysis, scatter plots, flow charts, histograms, control charts etc.

There are also multiple levels of expertise that have to be achieved to perform Six Sigma. The training depends on the level of education, experience and job standards. The levels are as follows:

  • White belt: It is the most basic level. The person should know the principles of Six Sigma.
  • Yellow belt: Here, the person is a team member and should know the methodologies.
  • Green belt: The person should understand tools and management. There should be a minimum of three years of experience in the field.
  • Black belt: The person should have proof of completion of at least two Six Sigma projects and lead problem-solving teams.
  • Master black belt: Here the person should have a minimum of five years of experience and should have proof of completion of at least ten Six Sigma projects. They should also be able to develop metrics and strategies to overcome problems.

What is Lean?

The Lean manufacturing process is commonly thought of as one that eliminates waste. In addition to that, Lean also helps streamline the process of manufacture and production. The ideas behind Lean were originally put forth by Henry Ford. Toyota implemented these ideas into the Toyota Production System (TPS), which further became one of the most efficient management systems in the world.

Similar to Six Sigma, Lean serves to make production more efficient. It does so by mapping out the operations in detail, finding the flaws and considering every aspect of the procedure through the eyes of the customer.

There are five principles of the Lean method. They are as follows:

  1. Understand the value: Focusing on the customer, the value of the product from the perspective of a customer is taken into consideration. This helps evaluate how much the customer is willing to spend on the product. The optimum price is thus decided so that it benefits both – the customer and the company.
  2. Mapping the value stream: Here, the flow of information and materials from one process to another is examined. It helps detect any waste or identify new methods for improvement. The entire operation is thoroughly examined from the procuring of the raw materials to the disposal of the finished products.
  3. Creation of flow: This constitutes the maintenance of the process to the utmost efficiency by identifying the flaws and rectifying them regularly.
  4. The Pull System: The Pull System is when new projects are started only when there is a need or a demand for them.
  5. Continuous improvement: The process is continued till perfection is achieved. While ‘perfection’ cannot be achieved, it is striving for perfection that is given importance.

The Lean method identifies seven types of waste in the manufacturing process:

  1. Defects: These are errors that hamper the process of manufacture.
  2. Overproduction: Producing in excess than truly necessary.
  3. Waiting: The time wasted while waiting between the processes.
  4. Unnecessary actions: These are actions that employees or machines do that are unnecessary for production.
  5. Excess Inventory: When there is excess inventory that occupies excess space.
  6. Transportation: lack of streamlined transportation wastes resources of the company.
  7. Extra processing: performing excessive steps that do not help the manufacturing process.

In addition to this, Lean practitioners include ‘unutilized talent’ as the eighth waste. It is when all the talent in the group is not properly used.

Like Six Sigma, lean also uses various techniques and tools to aid the streamlining process like the poka-yoke and the 5S technique. Some other techniques are as follows:

  • Heijunka: This is the technique to level or smoothen the product to improve the flow of production.
  • Kanban: This technique is used to achieve the ‘just-in-time’ goals.
  • Jidoka: In this technique, the process is stopped till the error is rectified.
  • Andon: This utilizes a visual aid to alert the employees of the problem.
  • Cycle time: This is monitoring the amount of time it takes to complete a cycle.

Differences Between Six Sigma and Lean in Points

Following are the main differences between Six Sigma and Lean:

  1. Six Sigma is a manufacturing process that works to increase the efficiency of the process by eliminating waste. The Lean manufacturing process also aims at eliminating waste but it also streamlines the project.
  2. Six Sigma was introduced in the year 1986, whereas the idea of Lean was around for longer. The term ‘Lean manufacturing’, however, was coined in 1991.
  3. The concept of Six Sigma was put forth by Bill Smith and Mikel J. Harry. The idea of Lean was originally put forth by Henry Ford. The company Toyota later implemented Lean in their manufacturing processes.
  4. Six Sigma finds its etymology in the statistical term ‘Sigma’, which stands for standard deviation from the mean. Three deviations below the mean and three deviations above the mean constitute Six Sigmas, which is 3.4 defects per one million opportunities. On the other hand, Lean is named as such because it eliminates the excesses and streamlines the process.
  5. Six Sigma is more of a process that is oriented to eliminating wasteful practices, while Lean is more of a philosophy that is oriented to making an effective process to achieve the best product.
  6. Six Sigma strives to achieve perfection, whereas Lean strives to make the process as minimal as possible by making the best use of resources.
  7. The prime focus of Six Sigma is to eliminate waste, while the prime focus of Lean is to improve efficiency by reducing cycle time.
  8. Six Sigma endeavours to achieve consistent results, whereas Lean attempts to maintain a consistent workflow for efficient outcomes.


While Six Sigma and Lean are two different manufacturing processes, their end goal is the same. They work towards making the best product for the customer. Their approaches are where they differ. Six Sigma works by eliminating unnecessary practices and strives toward accomplishing perfection. It has two basic approaches – DMAIC and DMADV. Some different tools and techniques help Six Sigma in achieving its goals like – Brainstorming, the 5S system, the poka-yoke etc. There are levels of certification that signify the expertise a person has in performing Six Sigma. These levels are – white belt, yellow belt, green belt, black belt and master black belt.

The Lean manufacturing process, similar to Six Sigma, also eliminates wasteful practices. But it focuses more on the process. It improves efficiency by reducing faults and enhancing helpful actions. It regulates the workflow with better organization and employs similar tools and techniques to Six Sigma. Presently one can use the hybrid version of both – Lean Six Sigma – which, combines both the techniques. Thus, to make the best use of your day, perhaps, either of the techniques could be given a shot. Organising the day and activities with minimal distractions and minimal wasteful practices only serves to maximise the productiveness just like these techniques do.


  1. https://www.simplilearn.com/what-is-six-sigma-a-complete-overview-article
  2. https://www.techtarget.com/searcherp/definition/lean-production
  3. https://ctekleansolutions.com/blog/lean-manufacturing-explained/
  4. https://theleanway.net/what-is-lean
  5. https://gomingo.io/lean-vs-six-sigma-whats-the-difference/
  6. https://www.sixsigmadaily.com/six-sigma-vs-lean/
  7. https://tallyfy.com/lean-vs-six-sigma/
  8. https://www.naukri.com/learning/articles/six-sigma-vs-lean-six-sigma/


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"Difference Between Six Sigma and Lean." Diffzy.com, 2023. Tue. 06 Jun. 2023. <https://www.diffzy.com/article/difference-between-six-sigma-and-lean-271>.

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