Contents
- Index
Sigma Level
Measure of quality that directly relates to the defect rate. Six Sigma corresponds to 3.4 defects per million. Three sigma to 0.13% defective or 1300 defects per million.
For process tolerances, the sigma level is the worst-case Z-score + 1.5. When there is a +/-1.5 SD operating window for the average, the sigma level is the on-target Z-score.
For statistical tolerances, the sigma level is the Z-score + 1.5.