What is Six Sigma?

Picture of Andrew Lavender

Published on 12 May 2020 at 16:15

by Andrew Lavender

What is Six Sigma - Life QI


Six Sigma is a systematic approach to improvement, focused on reducing variance and eliminating defects. Six Sigma has its roots in manufacturing and was developed by Motorola in the 1980’s to reduce defects in its factory processes.


In recent years, it is increasingly common that the Six Sigma approach is combined with elements of the Lean method, referred to as Lean Six Sigma. The processes are complimentary as where Six Sigma focusses on eliminating defects and reducing variation, Lean is focussed on improving flow and eliminating waste.


Fundamental to improvement with Six Sigma is the DMAIC (Define, Measure, Analyse, Improve and Control) framework. DMAIC is a five-phased data-driven method for improving, optimising or stabilizing existing processes.  Whilst it is a key tool in the Six Sigma methodology it is also widely implemented on its own.


The Six Sigma Method


The DMAIC framework lies as the heart of Six Sigma and provides a step-by-step approach to achieving sustained improvement.


What is Six Sigma - 02



The first step is to clearly define the problem to be solved and to get a clear understanding of the process in its current state. Typically, a project charter is initiated which includes a problem statement, business case, goal statement, timeline and scope.



Here, metrics are chosen to accurately assess the current state of a process and to use to quantify future improvements.  This includes choosing appropriate measures and collecting a baseline dataset to which the results of any improvement effort can be compared.



The data collected in the measure phase are examined to determine the root cause of the problem and identify areas for improvement.



The learning from the previous three phases is applied here to determine exactly the process could be improved. These solutions are tested to ensure they deliver the desired results.  Successful solutions may then be implemented.



This is where steps are taken to ensure successful improvements are sustained over time and don’t reverting back to the ‘old way’. This includes continued monitoring of key measures and the embedding of the improvements through the modification of systems (like documentation or training)


Starting the process

Where multiple problems are being faced, and capacity is limited, the initial step is to decide which problems to tackle first.  To do this, some organisations add a ‘Recognise’ step at the start of the DMAIC process – this is designed to evaluate the various problems being faced and ensure focus and effort is put on the most pertinent problem.


Benefits of Six Sigma

  • The end goal of every Six Sigma is near perfection in a process
  • Six Sigma puts strong focus on understanding the real cause of a problem and focussing improvement effort where most impact can be made
  • Emphasis is put on continuous education through the Belt Certification system
  • More emphasis is put on financial returns than in other models


Should I use the Six Sigma method?

Six Sigma strives for near perfection in processes – this zero tolerance for mistakes mean it is well suited for healthcare improvement. This is particularly true in improvement focussed on minimising medical errors. Because so much effort is put into the preparation part of the process, DMAIC is perfect for large or complex improvement projects that come with big risks or will be expensive to implement.


The approach is sometimes criticised for being too rigid in nature, therefore limiting the scope of projects to which it can be applied and making it slow to recognise improvements.  Whilst big focus is put on understanding the problem, the Six Sigma process is largely linear, particularly when compared to other techniques such as PDSA which aim for incremental change.


Typically, Six Sigma is used by organisations where the methodology is formally incorporated, directed by highly trained certified individuals (using a martial arts derived belt grading approach), and is less applicable on an ad-hoc basis.


These are some of the reasons that it is commonly combined with elements of the Lean methodology in a hybrid, Lean Six Sigma approach.


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