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Six Sigma vs. Other Process Improvement Methods

Six sigma

Six Sigma can be an excellent method for improving quality in business processes, but it isn’t a cure-all and it can’t be applied everywhere. 

In this article, we’ll learn what Six Sigma is, what its benefits are, when it should be used, and when to consider other tools.

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What Is Six Sigma?

Six Sigma is an approach to process improvement that focuses on quality.

Its focus is on minimizing variability and defects in a process or product. 

This method was originally developed at Motorola by the American engineer Bill Smith. Although it was originally designed for and applied to the manufacturing industry, Six Sigma can be used to manage business processes, improve performance, reduce costs, and more.

Here are a few key tenets of this approach:

  • Predictable, stable process results are essential for success in a business
  • Business and manufacturing processes can be clearly defined, measured, analyzed, and controlled
  • Quality improvement requires commitment from the entire organization
  • Decisions should be based on quantifiable measurements, data, and statistics

Like lean, Six Sigma is built around concepts such as continual improvement. There are differences, however – Six Sigma, for instance, focuses on reducing variability and defects, while lean focuses on reducing waste.

There are two core methodologies, or frameworks, followed in Six Sigma:

  • DMAIC. DMAIC is used to improve existing business processes. This framework, an acronym, covers key steps that include: defining the system and the project goals, measuring the key aspects of the process, analyzing the data to understand relationships and the defect being considered, improving the process based on collected data, controlling the future state and continually monitoring the process.
  • DMADV. DMADV is the framework aimed at developing new projects or business processes. It too is an acronym that stands for the key stages in this process. Its stages focus on: defining design goals, measuring key characteristics and capabilities, analyzing alternatives, designing an improved alternative, verifying the design.

Six Sigma goes further than just improving and systematizing business processes, however. It also prescribes a management approach, or hierarchy that should be implemented within the organization. 

Following the terminology used in the Japanese martial arts, these ranks include “belts,” such as green belts, black belts, champions, and executive leaders. Each has a specific role to play in the quality improvement process and the successful implementation of Six Sigma depends on their contributions.

Six Sigma vs. Other Process Improvement Methods

Six Sigma is, as mentioned, only one of many process improvement methodologies.

Others include:


Lean, like Six Sigma, drew heavily from Japanese influences, most notably the Toyota production methodologies employed in the 1930s.

The term “lean” was coined and its precepts weren’t codified until the 1980s and 1990s, however.

According to James Womack and Daniel Jones, the key principles of lean are:

  • Precisely specify value by specific product
  • Identify value stream for each product
  • Make value flow without interruptions
  • Let customer pull value from the producer
  • Pursue perfection

These five key principles are aimed at reducing waste and maximizing the value customers receive from a product or service. 

Today, lean has been applied to a wide range of business processes, from management to product development to business creation.

As pointed out, however, a key distinction between lean and Six Sigma is the focus on waste reduction in processes, rather than on minimizing variability and creating defect-free products.

Incidentally, some have also attempted to combine lean with Six Sigma – unsurprisingly resulting in a method known as “Lean Six Sigma” – in order to obtain the best of both worlds.


Agile has been compared to both lean and Six Sigma, but it is important to understand that agile is not a methodology, per se. 

Instead, agile is a set of principles that began in the software development world and quickly spread to other business disciplines.

The “manifesto” that started the agile movement emphasized principles such as:

  • Individuals and interactions over processes and tools
  • Working software over comprehensive documentation
  • Customer collaboration over contract negotiation
  • Responding to change over following a plan

These same principles have been reiterated and re-articulated multiple times over the years, but the core values remain the same.

Namely, agile strives to deliver more usable and useful products and services by staying nimble and by focusing on customer success.

How to Choose the Right Process Improvement Methodology

When evaluating process improvement methods, keep a few things in mind:

  • Each process improvement method has its own use case, as well as its own drawbacks and advantages
  • In some cases, different methods can and should be combined
  • There are other improvement methodologies besides those covered here, such as total quality management (TQM)
  • When implementing a process improvement methodology, they should be customized to suit one’s own business needs

When choosing a methodology for performance improvement or process improvement, start by understanding your own goals, clearly defining that method’s purpose, and seeing how well that method aligns with your aims. The more closely a method fits with existing aims and principles, the more suitable that approach will be.

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