| Flap 1 | Flap 2 |
| standard deviation | square root of the variance |
| mean | arithmetic average |
| coefficient of variation | standard deviation divided by the mean |
| shift | six results on one side of mean |
| trend | six results in one direction |
| 1 2s rule | 1 control exceeds 2 SD (warning rule) |
| 1 3s rule | 1 control exceeds 3 SD (reject rule) |
| 2 2s rule | 2 control levels exceed 2 SD (reject rule) |
| R 4s rule | 2 control levels in same run exceed 4 SD in opposite directions (reject rule) |
| 4 1s rule | 4 control levels exceed 1 SD on same side of mean |
| 10 x rule | 10 control levels on the same side of the mean |
| warning rule | evaluate other rules if no other rule is violated, run is accepted |
| reject rule | reject run and troubleshoot to find problem |
