Six Sigma - Quality Improvement Approach

A popular way for managers to put quality management into effect

This is an approach to quality improvement based on the statistical work of Joseph Juran, one of two American pioneers of quality management in Japan. Sigma is a Greek letter used in mathematics to denote standard deviation, a statistical measure of the extent to which a series of numbers or readings deviates from its mean. One Sigma indicates a wide scattering of the readings. If the mean is the required quality standard of a particular process or product, then One Sigma quality is not very good. The higher the number, the closer the readings come to total perfection. At the Six Sigma level, there are only 3.4 defects per million.

This may sound complicated, but in practice it has proved a popular way for managers to put quality management into effect. One of its great advantages is that it eschews the idea of aiming for “zero defects”, or total perfection—a dauntingly inaccessible goal for most. It presents a system for improving quality gradually. Companies or operational groups move step-by-step up the Sigma ladder, the ultimate goal being to reach the Six Sigma state—still just short of perfection. Reasonably unsophisticated computer programs do the necessary calculations when fed with data on the goals (the specifications of the perfect product or process) and the organisation’s actual achievements.

Six Sigma sounds like some sort of secret coven. Its advocates insist that it is no such thing. But it has certain attributes of the exclusive society. Anyone in an organisation who goes on a basic training course for a Six Sigma programme (and training is essential to an understanding of what it is about) is called a Green Belt. Anyone who is given the full-time job of leading a team that is embarking on a Six Sigma exercise is given further training and is called a Black Belt. Beyond this there are a special few who are trained even more, and they are called Master Black Belts. Their role is to champion the exercise throughout the organisation and to watch over the Black Belts and ensure that they are consistently improving the quality of their team’s output.

In its annual report for the year 2000, chemicals giant DuPont reported:

Six Sigma implementation continues to gain momentum. At the end of the year, there were about 1,100 trained Black Belts and over 3,400 active projects. The potential pre-tax benefit from active projects was $700m.

Pioneered in the United States by Motorola in the 1980s (and registered by the company as its own trademark), Six Sigma became hugely popular in the 1990s after Jack Welch adopted it at General Electric. Mikel Harry and Richard Schroeder, the two men who introduced the method to Motorola, went on to set up the Six Sigma Academy, a consultancy which has worked with such companies as Allied Signal, GR and ABB.

To achieve Six Sigma quality at GE, a process must produce no more than 3.4 defects per million “opportunities”. An opportunity is defined as “a chance for non-conformance, or not meeting the required specifications”. The company says: “Six Sigma has changed the DNA of GE. It is now the way we work—in everything we do and in every product we design”.

However, Six Sigma has not been an unmitigated success for everybody. Robert Nardelli took it with him when he moved from GE to head up Home Depot. But in August 2007 the Wall Street Journal reported that he had angered employees greatly with his attempt to force it upon them. Nardelli went on to try to resuscitate General Motors.


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