| Number of factors (K) | Limit |
|---|---|
| 9 ≤ K ≤ 13 | 6 interactions at most between 3-level factors with a common factor |
| 14 ≤ K ≤ 15 | 5 interactions at most between 3-level factors with a common factor |
| 16 ≤ K ≤ 17 | 4 interactions at most between 3-level factors with a common factor |
| 18 ≤ K ≤ 19 | 3 interactions at most between 3-level factors with a common factor |
| 20 ≤ K ≤ 21 | 2 interactions at most between 3-level factors with a common factor |
| 22 ≤ K ≤ 23 | 1 interaction at most between 3-level factors |
| K > 23 | No interactions between 3-level factors |