i value | Stone Size (mm) | n value |
0 | <2 | 1.0 |
1 | 2 ÷ 20 | 0.8 |
2 | 20 ÷ 50 | 0.6 |
3 | 50 ÷ 150 | 0.4 |
4 | 150 ÷ 400 | 0.2 |
5 | >400 | 0.0 |