Process improvement is the everyday job of a manager and might even be the sheer focus of the function. It can be easy to be overwhelmed by the number of methodologies that are available. This article aims to highlight some of them and explain their differences and specialisations, helping you find the right improvement methodology for you.



Starting with a nice exception, lean is not a methodology but rather a philosophy. Lean originates from the Toyota Production System (TPS) and was only named lean in 1990. It is  on this list because many people associate this philosophy with multiple well known process improvement tools such as Kaizen and JIT, which are all part of the lean house. What makes lean a successful philosophy is its systematic approach to waste minimization within a manufacturing system without sacrificing productivity. If you do not focus on flexibility and mostly want to increase efficiency lean is the way to go.


Six sigma

This methodology was introduced by engineer Bill Smith while working at Motorola in 1986. It focuses on the improvement of the output quality of a company. Using multiple empirical and statistical tools to improve the output quality and reduce the amount of defects. The name comes from manufacturing as the maturity of a manufacturing process can be described by a sigma rating. This rating indicates its yield or the percentage of defect-free products it creates. The ultimate goal of six sigma is to create a six sigma process which equals 3.6 defects per million opportunities. If your aim is to reduce variability in your process, whilst not directly focussing on efficiency and flexibility, then this might just be your methodology


Lean six sigma

As the name suggests this methodology combines the previously above mentioned methodologies. Most well known for its structured approach to optimisation, its DMAIC or DMADV structures are used all over the world. The name originates from a book published in 2001 titled Leaning into Six Sigma: The Path to integration of Lean Enterprise and Six Sigma by Barbara Wheat, Chuck Mills, Mike Carnell. The reason why these two methodologies work so good together is because lean is very effective in exposing sources of process variation whilst six sigma specialises in solving those. Thus creating a cycle which continuously improves a process. If you are looking for a structured approach to continuous improvement of efficiency and process variation this is your top pick.



An old methodology which was the previous big thing before six sigma back in 1980-1990. The reason for this is the lack of a structured approach. The methodology lacks any form standardised structure except for one similarity in all organisations: it is an organisation wide methodology. This is because the methodology aims to achieve long-term success through optimizing customer satisfaction, based on all members of an organization participating in improving processes, products, services and the culture in which they work. Whilst this methodology might not be the easiest to deal with, it has a proven track record and if you are looking for an organisation-wide approach for process optimization this could be your pick.



Last but not least a well known contribution from Eliyahu Goldratt. The Theory of constraints is an overall management philosophy introduced by Mister Goldratt in his 1984 book titled The Goal, that is geared to help organizations continually achieve their goals. It works by identifying the entire chain structure of a process, determining which link in that chain is the weakest and thus the constraint and then elevating these constraints. This methodology is widespread, proven and tested both theoretically and empirical which makes it a reliable method to optimise a process. If you are able to identify key locations in a process which are the limiting factor and you are also looking for a structured approach applicable in many fields, this should be your top pick.


Honorable mentions:

Zero defects (ZD) and Quick response manufacturing (QRM)


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