Lean vs Six Sigma: Getting the Best of Both Worlds

October 12, 2016

This post looks at the strengths and weaknesses of both Lean and Six Sigma and how they can complement each other.

There are different ways in which both Lean and Six Sigma can bring advantages to an organisation and help to drive improvements. However, the two methodologies do have different origins and hence take differing paths. In this post, we look at the strengths and weaknesses of both Lean and Six Sigma and how they can complement each other.

A combination of both Lean and Six Sigma provides effective means of solving problems and creating rapid transformational improvements at lower cost. Together they maximise value by achieving:

  • rapid improvement in customer satisfaction;
  • lower costs;
  • higher productivity;
  • higher quality;
  • faster process speed; and
  • the best use of resources.

Lean focuses on dramatically improving flow in the value stream and eliminating waste, while Six Sigma focuses on eliminating defects and reducing variation in processes. So let's break this down further and look at the specific strengths and weaknesses of both.

Lean: Strengths

  • Easy to understand methodologies that follow a guided “common sense” approach that is attractive to all levels within a business.
  • A step by step approach that gives incremental movement forward.
  • Rewards can be seen quickly, so build on is easy.
  • A very visual approach that is engaging and progress is clear.
  • Easy to build team enthusiasm.

Lean: Weaknesses

  • 'Value' can be a relative term, it is sometimes difficult to establish true customer value.
  • Has to be properly focused to prevent going down the wrong path.
  • If environment is not changed, it is easy to slip backwards. It is a journey and not a flavour of the month.
  • Not seen as being rigorous. Sometimes the perception is that data is not needed.

Six Sigma: Strengths

  • Relies on rigorous statistical analysis that leads to fact-based analysis.
  • Method focuses on key factors and tries to solve problems associated with these.
  • Control stage ensures that proper process control methods are put in place.
  • In addition, control plans prevent relapses.

Six Sigma: Weaknesses

  • Some customers don’t have clear specifications, making capability analysis difficult.
  • Statistical analysis is difficult if the process is not ‘in control’ or the process is not stable.
  • Process outcomes may not be normally distributed.
  • Difficult to use when outcomes are subjective – reliant on numerical methods.
  • Needs statistical expertise that demands high levels of specialised knowledge and wider training to understand the consequences.
  • Takes a long time to see results – typically 3 to 12 months for a team project.

Advantages of running Lean and Six Sigma together

Lean can bring the “broad brush of change” that is needed to an organisation and Six Sigma can apply the surgical precision to problem solving.

  • Lean does not explicitly prescribe the project set up and roles needed to achieve and sustain results.
  • Six Sigma provides a set of tools to understand problems and sources of variation, whereas Lean does not recognise the impact of variation.
  • Lean is not as strong in the measure and analyse stages of DMAIC.
  • Lean identifies waste. Six Sigma sub-optimises processes (Lean applies a systems approach).
  • Lean improves process speed/cycle time.
  • Lean includes methods for rapid action (kaizen).
  • Six Sigma quality is approached faster if Lean eliminates non value-added steps.

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Tagged: Lean