Six Sigma and Lean are complementary methodologies and, in fact, they overlap a great deal. However, it’s important to recognize there are important differences between the methodologies as well. First, let’s think about the focus. The focus of Six Sigma is around eliminating sources of variation, the number of mistakes and defects we’re making. As opposed to Lean, where we’re trying to take unnecessary time out of the process and eliminate waste wherever it happens. The methodology associated with Six Sigma suggests a very rigorous five step process. Define, measure, analyze, improve, and control, where we’re gathering the data and going through a number of different steps that are highly rigorous and very oriented around data. With Lean, we’re less focused on the data, at least the precision of it. Lean uses a four step process of identifying the end-to-end value stream. Identifying the opportunities to improve the overall end-to-end performance, designing a solution, implementing the solution, and taking steps to make sure that the improvement is continuous and lasting. In Six Sigma, we tend to be very focused on a point in the value stream. The performance, say, of a single step and our ability to produce quality at that step. Lean, on the other hand, considers the entire process and what we can do to improve the process to deliver things faster with better quality and more efficiency at the same time.
The key tools associated with Six Sigma are narrowly focused on specific problems and very statistical in nature. We use metrics and statistical process control tools to bring things under control and keep them controlled. Using a Lean line of thinking, we might use tools like theory of constraints for identifying bottlenecks and removing them. The concept of removing muda, the Japanese word for waste, is another technique. We eliminate waste through the use of value stream mapping, pull systems, the 5S methodology, the notion of standard work, error proofing, creating flow, and more. The success of Six Sigma depends on reliable data and scientific methods. This is a bit different than Lean, which is about eliminating waste and taking non-value added time out of the process wherever we can. On the Lean side, we’re less concerned with precision in the data. Instead, we’re seeking information about what to improve and why to improve it. It’s about total value stream performance and overall customer satisfaction.
Lean focuses on removing waste, improving the overall operation of the business, and being committed to continuous, small incremental improvements over time. In total, between both of these tool kits, there are more than 100 different defined tools that can potentially be learned and mastered in your learning journey. Zero defects and zero waste. We may never get there, but we want to be continually dedicated to improving quality. While at the same time working toward a totally waste-free value stream that delivers results that our customers want to pay for. Remember that all of this is inspired by the plan, do, check, act cycle of continuous improvement. PDCA and other methods like it tap into systemic problem-solving tools. The Six Sigma statistical tool bag, the DMAIC methodology. Other methodologies like the 5Ys. And additional tools like fishbone or Ishikawa diagrams and many more. Both Six Sigma and Lean depend on teams and people being motivated to come together and work toward a common purpose. Both require significant buy-in by the organization as well. Without that, we can’t get the commitment and the support required for success. Both methodologies, and particularly when they are leveraged together, are proven to deliver significant benefits and customer satisfaction, employee satisfaction, overall cost reductions, and making the company a better place to be.