Lean and Six Sigma are two methodologies that can and are frequently employed together.

Lean focuses on the breadth of a process, aiming to improve end-to-end ‘flow’ and reduce waste within a process. Six Sigma focuses on achieving an in-depth understanding of parts of a process in order to reduce variance and defects.
  • Both concepts have exactly the same objective: continuous business process improvement.
  • Both follow a structured approach to identify the root causes of a business problem and find the optimal solution to avoid recurrence of the problem.
  • Six Sigma improves the capability of steps that do add value whereas Lean focuses on eliminating waste.
  • Six Sigma is a data driven methodology, whereas Lean relies more on value stream maps and subsequent analysis.

What are Lean and Six Sigma and what are the key differences between them?

Lean

Six Sigma
Speed and efficiency by identifying value add and eliminating waste
Reducing variation, improving quality and stability by using a structured DMAIC approach
Realise more with less and at low costs
  • In a Lean process there is no ‘waste’ in terms of what is not valuable to the customer.
  • Activities are error proof, and defects are prevented. Workspace lay-out is optimal and easy to understand, everything is on-hand and easy to find.
Realise lower variation in a process/product quality
  • Six Sigma is a highly disciplined, quantitative, data-driven, fact based methodology focused on developing and delivering near-perfect products and services.
  • Six Sigma is a statistical measure of how far a given process deviates from perfection.
Voice of the customer
  • Business processes are viewed ‘end to end’ from the customers’ perspective – focus on what adds value to the customer.
  • Any activity in the workflow that adds time, effort or cost but does not create value to the customer is considered as necessary non value add and/or non-value add. These are considered two types of waste.
Voice of the customer
  • Similar to Lean, Six Sigma places the customer at the centre of process improvement to ensure customer’s needs are satisfied.
  • With the voice of the customer as a starting point Six Sigma focuses first on reducing process variance and then on improving the process capability.
Improve the whole system
  • Lean focuses on the end to end process and does not typically seek to improve the activities that create existing value for the customer.
  • Instead Lean seeks to identify and reduce waste to its lowest level by eliminating non value added activities (NVA) and minimising necessary non value added activities (NNVA).
Various diagnostic techniques
  • Six Sigma projects focus on improving the root-causes of the problem, instead of improving the symptoms.
  • Diagnostic techniques: Run and Control charts, ‘As-is’ process map, Critical to Quality Tree, Pareto Chart, Flowcharts, Histogram, Cause-and-Effect Diagram, Hypothesis Testing etc.