Six Sigma Vs. Lean Six Sigma: What Are The Differences?

By Indeed Editorial Team

Published 8 September 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Both Six Sigma and Lean Six Sigma are quality improvement approaches that members of quality management teams can learn to benefit their organisation. If you are planning a career as a quality management professional in the manufacturing, pharmaceutical, healthcare, finance or technology industries, you can benefit from these qualifications. Knowing the difference between these two methodologies can help you decide which certification is better suited to your career path. In this article, we define Six Sigma and Lean Six Sigma and share a thorough overview of the fundamental differences between Six Sigma vs. Lean Six Sigma.

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Six Sigma Vs. Lean Six Sigma

Before comparing Six Sigma vs. Lean Six Sigma, it is important to understand what they mean. Consider the following definitions:

What is Six Sigma?

Six Sigma is a business strategy and philosophy that helps companies gain a competitive advantage by reducing defects in their industrial and commercial processes. Some goals of the Six Sigma process include re-working and simplifying operations, reducing defects and rejections, shortening time to market, cutting down costs, improving customer satisfaction and upgrading the company's competitive position. The Six Sigma process reduces variation and ensures that 99.9% of the products manufactured are defect free.

A Six Sigma Certified professional is aware of the complete Six Sigma Body of Knowledge (BoK) and meets the requisite standard of proficiency. Sigma, a statistical term, helps a certified professional judge the current state of a process and its scope for attaining perfection. These individuals can identify errors in a process and also possess the skills to eliminate them.

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What is Lean Six Sigma?

The aim of Lean is to reduce time of processes and create a better flow. Lean improves speed, shortens the manufacture-to-delivery timeline and helps reduce waste. Lean Six Sigma is the fusion of the Lean and Six Sigma principles into one methodology that improves organisational performance. This business principle recognises the importance of stakeholders in every project's success and also emphasises data analysis to help those stakeholders understand the effectiveness of the workflow.

A Lean Six Sigma certified professional possesses a thorough understanding of both Lean and Six Sigma principles and knows how to integrate them to meet organisational requirements. Getting this certification usually requires individuals to have a certain level of experience and proven proficiency. These individuals possess enhanced problem-solving skills and are experts in identifying risks, errors or defects in a business process and removing them.

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Differences Between Six Sigma And Lean Six Sigma

To find out the difference between Six Sigma vs. Lean Six Sigma, you can consider the following factors:


Six Sigma is a program while Lean is a philosophy. Lean attempts to reorganise the culture and behaviour among employees, but Six Sigma does not attempt at organisational culture change. While Six Sigma proponents assert that waste results from variation within the process, Lean practitioners believe that waste comes from unnecessary steps in the production process that do not add value to the finished product. As a fusion of Lean and Six Sigma practises, Lean Six Sigma is both a program and a philosophy that attempts both organisational culture change and variation reduction.

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The goal of Six Sigma is to reduce variation for optimal quality control. It relies on data to identify problems in a business process. This management philosophy centres around ensuring that there are less than 3.4 defects per one million chances. Six Sigma reduces process variations by applying scientific problem-solving, utilising robust project chartering, concentrating on quality issues and employing technical methodologies. The focus of Six Sigma is on the customer and the end product.

Lean Six Sigma classifies any resource that does not add value to customers as waste, which has to be eliminated. Lean management relies on people to identify what problems are causing waste. According to this management philosophy, waste is of eight types, namely, defects, overproduction, waiting, non-utilised talent, transportation, inventory, motion and extra-processing. Lean Six Sigma aims to refine the production process by reducing the eight wastes. It focuses on waste and production methods.

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Six Sigma projects follow two project methodologies, each with five phases. These are the define, measure, analyse, improve and control (DMAIC) and the define, measure, analyse, design and verify (DMADV) methodologies. DMAIC is a data-driven method used to decrease defects and improve the manufacturing or delivery of an existing product or service for increased customer satisfaction. DMADV develops new defect-free methods for product manufacturing or service delivery for building new products or services or redesigning existing product or service manufacturing processes, in case existing processes do not meet customer conditions, even after optimisation.

Lean Six Sigma uses only the DMAIC methodology. But, unlike Six Sigma, it uses DMAIC along with the Lean philosophy. In particular, Lean Six Sigma follows five Lean principles at its core, which are:

  • Working for the customer: The primary goal is to deliver maximum benefit to the customer. This is possible by establishing a clear standard of quality defined by customer or market demands.

  • Finding and focusing on the problem: There are usually no attempts to alter the company or change the product extensively. Instead, experts gather data that shows specific problem areas and they concentrate on refining only those particular areas of the business.

  • Removing variation and bottlenecks: After identifying the problem, Lean Six Sigma professionals find out effective ways to decrease opportunities for defects. This involves streamlining long, intricate processes to remove mistakes and achieve quality control and efficiency.

  • Communication and training: All involved members receive Lean Six Sigma training, know the goals of a project and remain informed of its progress. Clear communication and specialised focus are required on behalf of the management to ensure smooth process operation and reduce the risk of project failure.

  • Flexibility and responsiveness: Faulty or inefficient processes are usually either refined or removed. Change and change management takes utmost importance to create a leaner, stronger, more competitive company.

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Six Sigma benefits organisations looking to reduce errors and operational costs and increase efficiency, regulatory compliance, cash flows and customer satisfaction. As a versatile methodology, it applies to almost all industries. Six Sigma proficiency can equip employees to find the root causes of problems with the help of data and statistics and help them find out how to develop effective solutions to address those issues. It gives them an understanding of the what, where and why of everything in the process chain. Employees can develop their knowledge and confidence, which improves the quality of the people in the organisation.

Lean Six Sigma is beneficial for companies looking to streamline their processes, reduce costs and offer the highest value to the customer. It offers huge transformation opportunities across all industries. Employees are also often highly engaged during process improvements, which can increase team spirit, accelerate development and improve organisational performance. They gain a better understanding of their contribution to business success and develop a deeper appreciation for the work of other employees and departments.

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Certification process

Both Six Sigma and Lean Six Sigma offer certification at five levels of training. This involves a belt classification system starting from the white belt and going towards the yellow, green, black and master black belts, with increasing levels of expertise. You can get your Six Sigma certificate from an accredited body, like the American Society for Quality (ASQ), the International Association for Six Sigma Certification (IASSC) or the Council for Six Sigma Certification (CSSC). For Lean Six Sigma certification, though, you can only get certified by the IASSC.

The duration and cost of each certification depend on the belt level and the accreditation institute. It is advisable to compare the duration and costs at different institutions before deciding anything.

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Professional utility

There is a marked difference between Six Sigma and Lean Six Sigma in terms of ownership. In Six Sigma, the onus of implementation is on special-purpose teams and Six Sigma experts who are in charge of the process. But Lean Six Sigma has to be adopted by everyone in the entire process chain as it aims at continuous improvement across the entire value stream of operations.

If you have considerable professional experience in supporting quality improvement projects, Six Sigma certification can be a good choice for you. Depending on your level of proficiency, you can start with the yellow or green belt and progressively move towards higher levels. If you are yet garnering professional experience, especially in quality management, a Lean Six Sigma certification may be an effective choice for you to advance your career.

Please note that none of the companies, institutions or organisations mentioned in this article are associated with Indeed.

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