| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per month | 6 |
16.2%
|
| 2 | 2. Per semester | 4 |
10.8%
|
| 3 | 3. Per year | 25 |
67.6%
|
| 5 | 5. Others | 2 |
5.4%
|
| 6 | 6. None | 0 |
0%
|
| 9 | 9. Missing | 0 |
0%
|
| Sysmiss | 195 |