Statistical Process Control ยท Western Electric Rules ยท Cp/Cpk Capability ยท Autonomous Verdicts
| Metric | Cp | Cpk | Rating |
|---|---|---|---|
| Run evaluation first | |||
| Rule | Condition | Severity | Indicates |
|---|---|---|---|
| WE1 | 1 point beyond 3ฯ | Out of Control | Special cause โ outlier event |
| WE2 | 9 consecutive points same side of center | Out of Control | Process mean shift |
| WE3 | 6 consecutive points steadily increasing/decreasing | Warning | Progressive trend or drift |
| WE4 | 2 of 3 consecutive points beyond 2ฯ (same side) | Warning | Increased variability |
| WE5 | 14 consecutive points alternating up/down | Warning | Stratification / mixing |