| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per day | 4 |
0.3%
|
| 2 | 2. Per month | 8 |
0.6%
|
| 3 | 3. Per semester | 10 |
0.8%
|
| 4 | 4 Per academic year | 511 |
39.5%
|
| 5 | 5.Per one school period | 753 |
58.1%
|
| 9 | 9 |
0.7%
|
|
| Sysmiss | 5286 |