Six Sigma vs Lean : Differences & Perspectives

In the new industry era, companies seeking for improving their productivity should think about adapting a management approach. At this stage, Six Sigma or Lean methodologies have likely been on their mind. Efficiency, value, and productivity can all be raised in an organization by implementing Lean or Six Sigma methodologies. Most professionals have carried out a solid perspective about the best method to use. Six Sigma or Lean? This topic has known some valuable debates.

Lean and Six Sigma share a lot of similarities, but they also differ in several fundamental ways. In this article, we define Lean and Six Sigma, evaluate the two methodologies, and get deep in the similarities and differences between them from various perspectives.

Six Sigma : Definition and Principles

Six Sigma was established in the middle of the 1980s by Bill Smith, an engineer at Motorola. In 1988, Motorola received the Malcolm Baldrige National Quality Award, which led to an increased interest of six sigma in other organisations. Today, a number of multinational organizations have implemented their own six sigma programs, and the methodology is now widespread across practically all industries, which created a remarkable rivalry with the Lean approach.

By focusing on process outputs that are critical in the customer’s perspective, the Six Sigma business improvement approach aims to identify and eliminate causes of defects or faults in business processes. The process average can be changed using Six Sigma methods, which can also help develop sustainable products and procedures as well as lessen process variation that results in mediocre quality. Six Sigma is a statistically based problem-solving process that uses data to drive solutions and provide impressive profitability. The main goal of six sigma is that only 3.4 per a million customers should be unsatisfied.

Six Sigma projects are led by full-time improvement engineers or managers known as “Black Belts” or part-time improvers who are frequently from supervision known as “Green Belts”. These make use of an impressive strategies:

  • DMAIC: Stands for “Define, Measure, Analyze, Improve, and Control”. Companies employ DMAIC to pinpoint current problems, assess how their processes are affecting those problems, and then refine those processes for long-term performance.
  • DMADV: Stands for “Define, Measure, Analyze, Design, and Verify”. An organization can utilize DMADV, which is similar to DMAIC, to recognize and assess current difficulties. But with DMADV, organizations can then design a completely unique procedure or solution to address these issues.

To better understand the different approaches of each method, we should then dig briefly in the history of Lean.

The History of Lean

Lean’s roots can be discovered in the Toyota Production System (TPS). TPS has a reputation for efficiency, quality, and employee involvement going back to the middle of the 1950s. In many industries today, lean has come to represent excellence and efficiency. Lean essentially works to cut waste and raise the quality of operational processes.

Lean focuses on identifying the value-added of any process by distinguishing between activities or stages that add value and those that don’t, then eliminating waste to ensure that every step provides value to the process. Lean emphasizes effectiveness, striving to produce services and products as quickly and affordably as feasible. To increase process flow and efficiency, lean commitment must begin at the top management level and propagate down to various levels within the organization. Lean strategy offers a collection of reliable tools and methods to cut down on hidden manufacturing wastes such lead time, inventory, setup periods, equipment downtime, scrap, and rework.

The core of difference between Lean vs Six Sigma is the way they tackle and eliminate wastes and defects. Lean identifies seven areas of waste that are known as the Seven Mudas or the Seven Deadly Wastes:

  • Transport: It doesn’t add value to the product, organizations pay employees to transfer materials from one place to another, a practice that just adds to their expenses and generates no revenue for them.
  • Inventory: Every product that is related to raw materials, works-in-progress, or finished items has a cost, and that cost is your responsibility up until the point at which it is actually sold.
  • Motion: Man or machine movements that are not as quick or simple to accomplish as they might be, are considered unnecessary motions. All of these inefficient actions waste your time and money while also taxing your staff and equipment.
  • Waiting: The period of time between each production step is known as waiting. When workers are kept waiting, nothing is being added in value.
  • Overproduction: Working with large batches, lengthy lead times, unsatisfactory supplier relationships, and a variety of other factors are frequently responsible for overproduction.
  • Over-processing: The waste of over-processing occurs when we employ improper techniques, oversized equipment, work with too-tight tolerances, carry out procedures that the customer does not demand, and so forth.
  • Defects: Every defective product involves rework or replacement, wastes materials and resources, generates paperwork, and may result to lost customers. And it’s also considered the ultimate goal of Six Sigma as well.

In the following section, we discuss some similarities and differences between Six Sigma vs Lean from various perspectives.

Six Sigma vs Lean : Process view and approach

In order to reduce variance, improvement projects under a Six Sigma program are carried out at various levels of complexity. The improvement is presented to the company’s top managers once the project participants have decreased variation in a process and thereby achieved the business goals, raised the profit, or decreased the cost. Some of the top managers often participate in the improvement projects that are conducted. As a result, the company’s top managers give the Six Sigma program the support it needs because they understand its economic benefits.

Contrarily, the discipline of Lean focuses on the flow, or the speed and efficiency of processes, in an effort to raise customer value. Project groups are typically used in lean manufacturing to make the necessary modifications.

Six Sigma or Lean? From a methodology perspective

There are two main methodologies for process improvement in six sigma, one for new processes and one for existing processes, as we have discussed in definition section. However, Lean could be regarded as a methodology when talking about its principles. One could argue that the methodologies in Six Sigma are a further development of the improvement cycle PDCA developed by Shewhart and Deming, which makes Six Sigma methodologies cyclical and consist of similar phases. Unlike Lean principles, as they are not cyclical in nature and are not focused on how to perform improvements. Hence, the methodology perspective could emphasize the Six Sigma vs Lean debate.

Lean vs Six Sigma : Tools of implementation

The purpose of most improvement efforts is to use data in a proper way in order to find out what is wrong with the system and thus improve the system. In Six Sigma and Lean, there are many different tools that could be used in order to find out what is wrong with the system. Generally speaking, the integration of cutting-edge improvement tools with the methodology has been successful with six sigma programs. From extremely basic tools to more sophisticated statistical tools, the tools vary from design tools to management tools. In six sigma training programs, participants learn how to pick the best tool for the job and how to use it. In order to ensure that the right tool was chosen, one must also double-check their choice. In general, six sigma programs have been successful in emphasizing the statistical aspect of quality management. In lean, a variety of tools are available for reducing or eliminating waste, however, the tools in the lean concept are more analytical in nature compared to the more statistical tools used in Six Sigma.

Six Sigma projects or Lean projects? An effect analysis

The projects in a Six Sigma program are selected in such a manner that they are directly related to the aims or objectives of the organization. The needs of the customers are typically considered while setting the company’s business objectives. One must demonstrate that an improvement would lead to financial savings for the organization before beginning a Six Sigma project. As a result, every improvement made as part of a Six Sigma program is justified from an economic perspective. On the other hand, when initiating a lean project with the goal of reducing a process’ lead time, one first evaluates the requirements of the process as set forth by the client. As a result, in addition to cutting down on lead times, the improvement also aims to enhance client satisfaction. However, successful lean programs frequently result in increased productivity and a decrease in inventory.


The debate between Six Sigma or Lean may rage throughout the field of quality improvement. Both Lean and Six Sigma are quality/cost improvement approaches which are fundamentally focused on processes. The degree of training and level of statistical expertise are the key distinctions between these two methods. Lean is generally focused on handling low hanging fruit with rapid answers, whereas Six Sigma is focused on dealing with more complex problems where unpredictability has been the main worry. As a result, the time frames for the implementation of both approaches differ greatly. Compared to Six Sigma, Lean is considerably easier for senior managers to understand. Due to project timelines and complexity, Six Sigma needs more real involvement from senior management to continue.

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Youssef is a Senior Cloud Consultant & Founder of

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