Statistical Process Control
3-sigma table
| n | A2 | D3 | D4 | d2=R/s |
| 2 | 1.88 | 0 | 3.268 | 1.128 |
| 3 | 1.023 | 0 | 2.574 | 1.693 |
| 4 | 0.729 | 0 | 2.282 | 2.059 |
| 5 | 0.577 | 0 | 2.114 | 2.326 |
| 6 | 0.483 | 0 | 2.004 | 2.534 |
| 7 | 0.419 | 0.076 | 1.924 | 2.704 |
| 8 | 0.373 | 0.136 | 1.864 | 2.847 |
| 9 | 0.337 | 0.184 | 1.816 | 2.97 |
| 10 | 0.308 | 0.223 | 1.777 | 3.078 |
| 11 | 0.285 | 0.256 | 1.744 | 3.173 |
| 12 | 0.266 | 0.284 | 1.717 | 3.258 |
| 13 | 0.249 | 0.308 | 1.692 | 3.336 |
| 14 | 0.235 | 0.329 | 1.671 | 3.407 |
| 15 | 0.223 | 0.348 | 1.652 | 3.472 |
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