| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Only once | 17 |
73.9%
|
| 2 | 2. Every year | 2 |
8.7%
|
| 3 | 3. Once in 3 months | 2 |
8.7%
|
| 4 | 4. Every month | 2 |
8.7%
|
| 5 | 5. Others | 0 |
0%
|
| 9 | 9. Missing | 0 |
0%
|
| Sysmiss | 323 |