The origins of Six Sigma can be traced back to Johann Carl Frederick Gauss, (1777—1855) a legendary German mathematician and physicist. In 1818, he started working on normal distribution, which forms the basis of Six Sigma philosophy. The person who first coined the term “Six Sigma” was Bill Cohen, an engineer with Motorola. Later, in 1986, Bill Smith, a senior scientist at Motorola, standardized the way defects are measured using Six Sigma. A Six Sigma process is one in which 99.9997% of the products manufactured are statistically expected to be free of defects (3.4 defects per million). Instead of measuring defects in thousands of opportunities, Six Sigma provided the ability to measure defects in millions of opportunities—thereby providing significant improvement in quality.
Since that time, several companies, including Motorola, Citibank, General Electric, and Allied Signal, have achieved dramatic success using Six Sigma methodology to improve quality and reduce costs. As the Six Sigma score improves, the variation in the processes reduces drastically, thereby increasing the reliability of the system, which reduces the need for rework. The reduction in amount of rework reduces cycle time and improves customer satisfaction. (For example, Motorola has documented $16 billion in savings due to its Six Sigma efforts.)
There are several factors that make Six Sigma a more effective quality tool when compared with other traditional quality techniques, namely: