The Relationship Between Six Sigma and Lean Methodologies

When it comes to improving business processes, you've probably heard of two methodologies called Six Sigma and Lean. They both aim to reduce waste and defects, boost efficiency, and increase customer satisfaction. But are they two entirely different approaches or two sides of the same coin? In this article, we'll explore the relationship between Six Sigma and Lean, their similarities and differences, and how they can complement each other to achieve better results.

What is Six Sigma?

First, let's define what Six Sigma is. Developed by Motorola in the 1980s, Six Sigma is a statistical-based methodology that aims to reduce variability and defects in a process by identifying and eliminating root causes. Six Sigma's goal is to achieve a process capability of 3.4 defects per million opportunities (DPMO), which translates into a near-perfect defect rate of 99.99966%. Six Sigma practitioners use a robust set of tools such as DMAIC (Define, Measure, Analyze, Improve, Control) and statistical process control (SPC).

What is Lean?

Now, let's turn our attention to Lean. Lean is a methodology that aims to eliminate waste and increase value in a process by eliminating activities that do not add any value to the customer. It was initially developed by Toyota in the 1970s as part of the Toyota Production System (TPS). Lean practitioners use various tools such as Value Stream Mapping (VSM), the 5S methodology (Sort, Set in order, Shine, Standardize, Sustain), and Just-In-Time (JIT) to improve processes.

Similarities between Six Sigma and Lean

On the surface, Six Sigma and Lean might seem like two entirely different methodologies. However, they share a common goal: continuous improvement. Both methodologies aim to create a process that delivers high-quality products and services with minimal waste, defects, and delays. They both use data-driven approaches to analyze and improve processes. Six Sigma and Lean rely on collaboration and teamwork to solve problems and create a culture of continuous improvement. Besides, Six Sigma and Lean are customer-focused methodologies that seek to deliver products and services that meet or exceed customer expectations.

Differences between Six Sigma and Lean

Despite their similarities, Six Sigma and Lean have distinct differences in their approaches to reducing waste and defects. Six Sigma focuses on reducing variability and defects by identifying and eliminating root causes. It assumes that there is an optimal level of variability that can be achieved by minimizing process deviations. Six Sigma practitioners use statistical methods to track and control process output parameters and achieve a target performance level.

In contrast, Lean aims to eliminate waste by identifying and removing non-value-added activities or activities that do not contribute to the overall process value stream. Lean practitioners focus on optimizing the process flow and creating a continuous flow of value-added activities. Lean strives to achieve a pull-based, just-in-time (JIT) system that delivers products and services when the customer needs them, without waste.

How Six Sigma and Lean can complement each other

Although Six Sigma and Lean have different approaches to process improvement, they can be combined to create a powerful method for continuous improvement. The complementary aspects of Six Sigma and Lean are easy to see when you consider the DMAIC process, which is the core methodology of Six Sigma.


In conclusion, Six Sigma and Lean are two methodologies that share a common goal of achieving continuous improvement in business processes. Although they have different approaches to reducing waste and defects, their complementary aspects can be combined to create a powerful tool for process improvement. Practitioners who use Six Sigma and Lean together can take advantage of the strengths of both methodologies and eliminate waste, reduce defects, improve process efficiency, and increase customer satisfaction. If you're a Six Sigma practitioner, consider adding Lean to your toolkit, and if you're a Lean practitioner, consider adding Six Sigma to your arsenal. Together, they can take your process improvement efforts to the next level.

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