| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per month | 139 |
82.7%
|
| 2 | 2. Per semester | 8 |
4.8%
|
| 3 | 3. Per year | 19 |
11.3%
|
| 5 | 5. Others | 2 |
1.2%
|
| 6 | 6. None | 0 |
0%
|
| 9 | 9. Missing | 0 |
0%
|
| Sysmiss | 171 |