| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per month | 35 |
47.9%
|
| 2 | 2. Per semester | 7 |
9.6%
|
| 3 | 3. Per year | 29 |
39.7%
|
| 5 | 5. Others | 2 |
2.7%
|
| 6 | 6. None | 0 |
0%
|
| 9 | 9. Missing | 0 |
0%
|
| Sysmiss | 159 |