Lean, Six Sigma or Both?

Lean, Six Sigma or Both?

There is always a test of loyalty when one gets presented with a question about Lean and Six Sigma. I know it is easier to choose both given that the two concepts have different scopes but given a choice to pick just one of them, there are a few things to consider. It is not as easy as outrightly choosing one over the other in a blink of an eye.

From the very beginning, historically, the two concepts were developed at different geographical locations and from different organizations operating in different business jurisdictions. Lean, as lean manufacturing originally is credited to Toyota which is a Japanese company and Six Sigma originated from Motorola company which is American.

Lean as a concept cropped up out of Taichi Ohno’s Toyota Production System (TPS) developed together with Sakichi Toyoda and his two sons Kiichiro Toyoda and Eiji Toyoda. For Toyota, a car manufacturing company, to increase efficiency and value in the production line, Taichi identified the seven wastes (muda in Japanese) to be eliminated and came up with concepts such as takt time, Just In Time (JIT) and others.

Six Sigma on the other hand was conceptualized at Motorola, a wireless telecommunications company based in Illinois USA by two engineers Bill Smith and Mikel Harry. The key concept of Six Sigma has always been to reduce defects using a structured approach called DMAIC (Define, Measure, Act, Improve, Control).

So, what are the major differences to consider when wondering which concept to adopt or where to adopt it:


As indicated earlier, Lean is concerned majorly with reducing waste and increasing value for the customer. It is about focusing on the activities that the customer is willing to pay for. Anything outside this is a waste and needs to be eliminated. These wastes to be eliminated could range from overproduction, overprocessing, unnecessary transport, unnecessary motion, excess inventory, defects and waiting.

Six Sigma on the other hand is more about reducing variations which if uncontrolled or left unchecked results in too many defects. It is more about improving consistency in the quality of products which when looked at more deeply results in less reworks and improves reproducibility and traceability.


Lean as a concept largely fits into operational management. It is continuous, very versatile and very wide in terms of application. For instance, there is a concept such as kaizen which promotes the idea of continuous improvement and points to the fact that it is an ongoing process. The same could be said with perfecting the process using ideas such as Kanban, supermarkets, JIT, and Mura (reducing irregularity in production), which can be termed as standardizing operations.

Six Sigma has a narrower scope. It fits more in operational analysis. Looking at Mura in lean one may think that it sounds more like Six Sigma, but the tools of use show the differences between the two concepts. Six Sigma is more statistical and requires measurements and one attains the satisfaction of reduced variations when production measurements are restricted to within the calculated upper and lower limits.

Tools and their need

Thus, Six Sigma will employ a heavy use of statistical tools requiring measurements or collection of data and calculating standard deviation which helps in monitoring the variations. Charts and graphs are then used to present the data and show the dispersion of the product measurement relative to the set limits and means.

This would be aimed at identifying sources of variations and mistakes, evaluating them and working to improve stability and reduce those variations in shifts, and more importantly in the process. The reductions in variations follow design adjustments, followed by verifications and once satisfactory results are achieved implementations are done with the relevant controls in place.

Lean is largely about business concepts and principles whose measurements are more about meeting certain set targets. For example, it could be reducing the amount of time a product spends at a certain workstation or how much time an employer has to wait before they can start working on the next product in the production line and resolving those bottlenecks responsible for the delays.

This may mean looking at WIP (Work In Progress) to identify where the bottleneck originates in the line and find ways to address it. This also means looking at production line maps and redesigning them to ensure as little waste as possible while in turn maximizing customer value.

So, which one?

Lean Six Sigma?

As we have seen, there are major differences between Six Sigma and Lean. Which one to choose depends on the business needs at that moment. As many of us can agree, most businesses have adapted both concepts to meet their diverse needs.

Customers need to get value for what they are willing to pay but still get the best quality possible. Total Quality Management as a concept of Lean adopts aspects of Six Sigma to ensure there is consistency in quality by working on quality from the source of the raw material or by ensuring all parts received are within the tolerance limits for example. Within that, Six Sigma plays a huge role.

One fact though is that lean business principles are diverse and can be adapted to as many applications as possible beyond the manufacturing line to places such as offices, banking halls, educational institutions, airports et cetera. Six Sigma principles are narrower but also essential in reducing variability albeit at best within certain applications in defined sectors such as project management and the manufacturing industry.

So, instead of wondering which one to choose, adopt Lean Six Sigma.

Geoffrey Ndege

Geoffrey Ndege

Geoffrey Ndege is the Editor and topical contributor for the Daily Focus. He writes in the areas of Science, Manufacturing, Technology, Innovation, Governance, Management and International Emerging Issues. For featuring, promotions or support, reach out to us at info@dailyfocus.co.ke
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