| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 |
0%
|
| 7 | 1 |
25%
|
|
| 15 | 2 |
50%
|
|
| 20 | 1 |
25%
|
|
| Sysmiss | 341 |