The Six Sigma scale shows how well a vital feature performs compared to its requirements. The higher the sigma score, the more efficient the feature is. This table shows the universal Six Sigma scale:

Sigma Level (Z) Defects per Million Opportunities (DPMO) Percent Defects (%) Percent Success (Yield %) Capability (CP)
1 691,462 69 31 0.33
2 308,538 31 69 0.67
3 66,807 6.7 93.3 1.00
4 6,210 0.62 99.38 1.33
5 233 0.023 99.977 1.67
6 3.4 0.00034 99.99966 2.00