| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per month | 46 |
37.7%
|
| 2 | 2. Per semester | 30 |
24.6%
|
| 3 | 3. Per year | 20 |
16.4%
|
| 5 | 5. Others | 26 |
21.3%
|
| 6 | 6. None | 0 |
0%
|
| 9 | 9. Missing | 0 |
0%
|
| Sysmiss | 110 |