What is Six Sigma?

Six Sigma is a quality management program to achieve "six sigma" levels of quality. It was pioneered by Motorola in the mid-1980s and has spread to many other manufacturing companies. It continues to spread to service companies as well. In 2000, Fort Wayne, Indiana became the first city to implement the program in a city government.

Six Sigma aims to have the total number of failures in quality, or customer satisfaction, occur beyond the sixth sigma of likelihood in a normal distribution of customers. Here sigma stands for a step of one standard deviation; designing processes with tolerances of at least six standard deviations will, on reasonable assumptions, yield fewer than 3.4 defects in one million. (See below for those assumptions.)

Achievement of six-sigma quality is defined by Motorola in terms of the number of Defects Per Million Opportunities (DPMO).

That is, fewer than four in one million customers will have a legitimate issue with the company's products and service.

Many people believed that six-sigma quality was impossible, and settled for three to four sigmas. However market leaders have measurably reached six sigmas in numerous processes.