# What is Six sigma?

Posted by interview tipsMotorola developed a concept called Six Sigma. Six Sigma focuses on defect rates, as opposed to percent performed correctly.

“Sigma” is a statistical term meaning one standard deviation. Six Sigma means six standard deviations. At the Six Sigma statistical level, only 3.4 items per million are outside of the acceptable level. Thus, the Six Sigma quality level means that out of every **one million** items/opportunities **999,996.6** will be correct, and not more than **3.4** will be defective.

Sigma level Defects per million opportunities

Level 1 690,000

Level 2 308,537

Level 3 66,807

Level 4 6,210

Level 5 233

Level 6 3.4