| Value | Category | 
|---|---|
| -9 | Don't know (SPONTANEOUS) | 
| 1 | Possible to achieve without much effort | 
| 2 | Possible to achieve with some effort | 
| 3 | Possible to achieve with normal amount of effort | 
| 4 | Possible to achieve with more than normal effort | 
| 5 | Only possible to achieve with extraordinary effort | 
| Sysmiss |