Sigma value, Z value, and the Cp value
01/04/2021
Understanding of normal distribution
Z conversion
Z＝
Process capability index
Cp＝
| Sigma value | Z value | Cp value | DMPO |
| 1σ | 1 | 0.33 | - |
| 2σ | 2 | 0.67 | 308.537 |
| 3σ | 3 | 1.00 | 66.807 |
| 4σ | 4 | 1.33 | 6.210 |
| 5σ | 5 | 1.67 | 233 |
| 6σ | 6 | 2.00 | 3.4 |
In the short term: 6σ
In the long term: 4.5σ
DMPO: Defects per million opportunities ＝Value of normal distribution－1.5（One side）
Methods for Productivity Improvement (Example)
Author: Phan Nguyen
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