ISO 9001, Lean, TQM and Six Sigma – same same or different?

Man in front of manufacturing line for aeroplanes

I’ve been working with these tools, methodologies and requirements for over 30 years and I think they’re great. Like all management terms, they drift in and out of favour, get changed, manipulated, criticised, talked about by gurus, turned into training courses, and become hot topics at conferences.

But what are they, and are they the same thing with different names? Well, yes, they are and no, they’re not. The ‘yes’ is they are all about business improvement. They are about processes and managing them better, with the end result of reducing inefficiencies and making the customer happier. These tools do and can all work together.

The ‘no’ is they have different agendas or scopes. So we’ll talk about them individually.

ISO 9001 Quality Management System – requirements

ISO 9001 is the international standard for a Quality Management System (QMS) and it involves the entire organisation. It is a set of requirements that are recognised globally and are primarily focused on meeting customers’ needs.

Once an organisation has developed and implemented their QMS, they normally are audited by a Certification Body which issues them a certificate that states they comply with ISO 9001. The driver for having a QMS has traditionally been the customer – with customers, including government, requiring their suppliers to have ISO 9001.

ISO 9001, along with other international standards, is updated about every seven to eight years to reflect the changing world. The first ISO 9001 was published in 1987 following the British Standards BS 9000 in 1971, BS 5179 in 1974, and BS 5750 in 1979.

Whilst ISO 9001 is a set of requirements for a QMS, the International Organization for Standardization (ISO) has also produced requirements for an Environmental Management System (EMS) ISO 14001, a Food Safety Management System (FSMS) ISO 22000, and an Asset Management System ISO 55001. It is about to release, in early 2018, requirements for an Occupational Health and Safety Management System (OHSMS) ISO 45001.


It is great for identifying what means value for your customer.

The main purpose behind lean principles is to identify what adds value for the customer and stop doing, as much as possible, things that don’t add value. This is good for the business as it reduces costs, and good for the customer who can buy goods and services cheaper without any loss in quality.

The term “lean” was coined by Jim Womack from MIT to describe Toyota’s business during the late 1980s, and has been described in two great books:

  • The machine that changed the world. James Womack, Daniel Jones and Daniel Roos 1990
  • Lean Thinking. James Womack and Daniel Jones 1996.

Lean focuses management on optimizing the flow of products and services across entire horizontal value streams, rather than vertical departments or silos.

Identifying and eliminating waste and wasteful activities and tasks mean that less space, less human effort, less capital, and less time are needed compared with traditional business systems. Lean was initially focused on manufacturing but is now applied across all business types.

The driver for lean is normally a modern thinking member of the senior manager team.

There is no global standard to state that an organisation has adopted lean principles, although an individual’s competencies are covered in ISO 18404 and process improvement is covered in the ISO/NP 13053 series (see later).

Total Quality Management

Total Quality Management (TQM) was huge in the late 1980s and into the 1990s. It would be a hard sell now, and that is a shame. 

So why was TQM big then and isn’t now? Basically, it became unfashionable – it lasted about 10 years, then we needed something else (similar to wide ties, bell bottom trousers, coloured bathrooms and fondues).

TQM was a result of competition from Japan in the 1970s and was firmly focused on manufacturing and Japan’s ability to make high quality goods at a competitive price.

TQM was focused on improving processes to enhance customer satisfaction; and whilst there was no across the board definition of TQM, there was general agreement that the Plan Do Check Act (PDCA) Cycle advocated by Dr W. Edwards Deming should be used along with the following seven basic tools of quality:

  • Cause and effect diagram (also known as fishbone or Ishikawa)
  • Check sheet
  • Control chart
  • Histogram
  • Pareto chart
  • Scatter diagram
  • Stratification.

TQM was often championed by individuals within an organisation, then managed by voluntary teams, often called Quality Circles, which focused on particular processes within the business, normally in manufacturing/production.

As well as Deming, the main teachers or gurus who were pushing TQM included Dr Joseph Juran, Philip Crosby and Kaoru Ishikawa.

Six Sigma

Six Sigma essentially replaced TQM. It was championed by Jack Welch in 1995 when he was at General Electric and it became central to the GE business strategy. However, Six Sigma was first introduced by engineers at Motorola in 1986 and trademarked in 1993.

The term “Six Sigma” derives from statistical process control and process capability and aims to produce a reject rate of less than 3.4 defects per million opportunities (DPMO).

Six Sigma projects follow two project methodologies inspired by Deming’s PDCA Cycle:

  • DMAIC which is used for projects aimed at improving an existing business process.  Define – Measure – Analyze – Improve – Control
  • DMADV which is used for projects aimed at creating new product or process designs.  Define – Measure – Analyze – Design – Verify.

Within each phase of a Six Sigma project, the seven TQM tools are used along with other tools such as:

  • Cost – Benefit Analysis
  • Quality Function Deployment (QFD)
  • Root cause analysis
  • 5 Whys
  • Value stream mapping.

Six Sigma is very similar to TQM – some would say it’s the same. However, it differs in the way that it was used by people other than just volunteer production staff. Organisations engaged professional Six Sigma practitioners, and a hierarchy was established with people being ‘qualified’ at different levels: Master Black Belt, Black Belt, Green Belt.

There is now a proliferation of training courses in Six Sigma to ensure people use the correct methodologies.

Six Sigma tends to focus on individual projects within an organisation with the aim of saving money through stabilising processes and reducing defects and rework.

ISO has produced a number of publications which cover both Lean and Six Sigma:

  1. ISO 13053 series which describes the methodology, tools and techniques, and recommended best practice
  2.  ISO 18404 which defines the competencies for individuals: Black Belt, Green Belt and lean practitioners.

In summary

These tools are all similar, but like all tools, it’s about selecting the right one for the job. Which should you use? Well, it depends what you want it to do. And there is nothing wrong with using all these tools at once – they don’t conflict.

ISO 9001
This is great if you want a set of requirements to control your business using a systematic approach, and to demonstrate to others that your organisation has achieved this through being certified.
If you want your organisation to reduce costs, reduce waste and operate quicker, this is the one for you. It is great for identifying what means value for your customer.
Relatively simple and easy to understand, TQM is well suited for individual projects. It is a very good group of tools for problem-solving after things have gone wrong.
Six Sigma
This is best for high volume activities where stability is required. The tools are similar to TQM but more structured.



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