The History of Six Sigma

The second "pillar" of the Toyota Production System is jidoka, a system for detecting defects and abnormal conditions in production, automatically stopping a line so that quality issues can be quickly addressed.

In even the leanest manufacturing plants, some quality issues arise that are difficult to identify and correct. Six Sigma is especially effective at identifying the root cause of quality problems – and eliminating defects by reducing variation in manufacturing processes.

The quality tools and techniques that were named “Six Sigma” in 1986 by Motorola (actually by a Motorola engineer named Bill Smith) are not new. They were developed over the past 50 or more years, through the work of quality experts such as Deming, Juran and others.

Despite the use of the term today, Six Sigma is actually a numerical measurement of quality. To achieve Six Sigma, precisely 99.99966% of what you do must be without defects. From a manufacturing standpoint, that means just 3.4 defects per million products or parts made. Surprisingly, manufacturing 99% without defects means you’ll have 10,000 defects per million – and at 95% that number jumps to 50,000 defects.

See a timeline of the evolution of lean and Six Sigma.

Pareto Principle

Also known as the 80-20 Rule. First defined by J. M. Juran in 1950 and named after Italian economist Vilfredo Pareto, who observed that 80% of property in Italy was owned by 20% of the population. A Pareto chart is a graphical tool for ranking causes from the most significant to the least significant.