# Six Sigma

Operations · `Six Sigma` · verification: source checked

Six Sigma is a data-driven process improvement methodology aimed at eliminating defects in a process. Its target is a defect rate of 3.4 defects per million opportunities, a level corresponding to six standard deviations from the mean. Six Sigma projects follow the DMAIC sequence: Define, Measure, Analyze, Improve and Control.

## Specification

| Property | Value |
|---|---|
| Kind | methodology |
| Origin | Motorola, 1980s |

## Study notes

- Sigma is the standard deviation, a measure of variability in a process.
- The term Six Sigma refers to a process with a deviation of six standard deviations from the mean.
- The target defect rate is 3.4 defects per million opportunities (DPMO).
- A defect is defined as any process output that does not meet customer requirements.
- Certification levels listed are white belt, yellow belt, green belt, black belt and master black belt.
- Six Sigma projects use the DMAIC methodology: Define, Measure, Analyze, Improve and Control.
- The methodology uses data to identify root causes of defects and implements solutions that eliminate them.
- The name was first coined by Motorola in the 1980s to describe its quality control program.
- The document states certification does not necessarily indicate capability.
- The document states reliance on statistical analysis limits the number of people capable of effective practice, making training difficult to scale.
- Example project goal: reduce average customer service call wait time to no more than 2 minutes.

## Sources

1. [Six Sigma - A Resource Guide | Lean Enterprise Institute](https://www.lean.org/lexicon-terms/six-sigma/) (accessed 2026-10-25)

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