Glossary

Sigma

Tags: Glossary

A Greek letter (Σ) commonly used to designate the standard deviation of a population. Sigma is a statistical term that measures how much a process varies from perfection, based on the number of defects per million units produced. In a process audit measurement, sigma would be the number of times the process failed for each million time the process was run. In either case the subject is generally referred to as an “opportunity.”