# difference between sigma and standard deviation

#### sihem

##### New Member
please, what is the difference between sigma and standard deviation in quality control

#### noetsi

##### No cake for spunky
Sigma is the greek letter used to represent standard deviation. For example Six sigma, used often in the quality literature, means six standard deviations from the mean. In other words there is no generic difference, although specific individuals in the quality movement (many of whoom use terms pretty losely or differently from their initial meaning) might use the terms differently.

http://sixsigmatutorial.com/six-sigma-tutorial/7/

The above notes this. One "difference" is that sigma in quality is usually used to denote reduction of errors (by so many standard deviations from the process mean).