Six Sigma is a methodology for maximising value through minimising mistakes. Mistakes generate costs – cost of reworking a part made incorrectly, cost of losing a customer, efficiency losses, cost of making scrap, cost of unnecessarily complicated procedures etc. All businesses have these costs driven by wastes in their processes – and the costs can add up to as much as 20-30% of their revenue!

So, what is Six Sigma?

A Greek Symbol?

A Statistical Measure?

A Methodology?

A Business Philosophy for Continuous Improvement?

A Benchmark?

A Goal?

Well….yes, it’s all of these.

Many people quote 3.4 ppm (that’s parts per million) as the threshold for Six Sigma, but hey, if I am getting my measures at 99%; OK, surely that’s good enough…right?



Six Sigma has grown from its original purpose in the mid-1980s as a quality improvement methodology, to today’s general purpose approach to minimising mistakes – and hence maximising value. It is data-driven problem solving. It is a project-based approach rather than a business strategy, and follows a disciplined and gated process called DMAIC – shorthand for;


Unlike PDCA (Demings’ improvement cycle; Plan-Do-Check-Act), which is most often illustrated as a circular cycle that should never end, DMAIC is a linear project – with a defined start and finish point. Temporary teams are assembled to conduct Six Sigma projects, and project charters are developed to scope the problem, define the measure of success and record the resources and timescale agreed to get the results.

So, what about these DMAIC steps?

Some simple definitions…

Define the Problem (Management)
Define a clear Project Charter addressing a real problem that is relevant to the customer and will provide significant benefit to the business.

Measure the Process (6Sigma expert-led)
Measure the current performance against relevant KPIs and set a baseline for improvement.

Analyse the Process (6Sigma expert-led)
Find the Root Cause of the problem. Six Sigma talks about y=f(x) where the Y results from, or is a function of the Xs. If we think about a recipe, the Y may be a loaf of white bread for example, and the Xs are the flour, water, yeast, salt, mixing, resting time, baking temperature, baking time etc. All of these have quantities, specifications and tolerances. Get them wrong and your result is no good. Understand them and control them well enough and your product will consistently meet requirements. If you understand and can control the problems that impact the Xs, you can literally switch the problem on and off!

Improve the Process (6Sigma expert-led)
Identify, develop and implement the best solutions to countermeasure the identified Root Causes. Notice the improvement stage only comes in at step 4 – once the problem is thoroughly understood.

Control the Process (Process Owner)
Before the project can be closed, the Process Owner must ensure the process has robust controls ensuring the solutions are properly embedded – no repeat concerns!

But be careful, not every problem needs a Six Sigma project approach. Only use Six Sigma when….

• There is no known solution
• The Root Cause is unknown
• The problem needs statistical analysis
• The process is repeatable (i.e. we have already applied the standard Lean tools, such as Standardised Work, 5S etc.)
• There is data available (or we can obtain data)
• There is a financial benefit – a Six Sigma project takes time and resources!

Six Sigma requires discipline, effort and resources whilst going through the pain of change.

But the rewards can be the minimisation of mistakes, resulting in improved performance, better served customers, reduced costs and maximised value.

Industry Forum offers both Six Sigma Yellow and Green Belt certification, which are run as virtual courses, open to anyone, or can be run on your site as a closed course for organisations which require training for 4 or more delegates. Contact Us via the form on the left of this page should you wish to discuss Six Sigma programme for your organisation. 

– January 2020 authored by Mike Scull

A Bit More About Mike
Mike Scull has over 30 years of manufacturing experience within the automotive, aerospace, electronics, off highway, white goods and apparel sectors. Joining Industry Forum in January 1998, Mike underwent training and mentoring in the implementation of Lean Manufacturing with Japanese Master Engineers from Toyota, Nissan and Honda. Mike’s current role at Industry Forum is Principal Consultant – Lean Manufacturing.

Mike is a Chartered Engineer (CEng MIMechE), and has a BSc (Hons) in Civil Engineering. He has professional qualifications including APICS Certified Supply Chain Professional (CSCP) and Certified Production and Inventory Management (CPIM), Certified Demand Driven Planner, PRINCE2 Practitioner and is a Certified Six Sigma Black Belt. He is also an Assessor for the National Manufacturing Competitiveness Levels (NMCL) programme.

Click here to contact Mike.