| Value | Category | Cases | |
|---|---|---|---|
| -9 | do not know | 1 |
25%
|
| 0 | none' | 0 |
0%
|
| 15 | 1 |
25%
|
|
| 30 | 1 |
25%
|
|
| 31 | 1 |
25%
|
|
| Sysmiss | 144 |