| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 749 |
25.3%
|
| -7 | Does not apply (spontaneous) | 284 |
9.6%
|
| 1 | Very easy | 103 |
3.5%
|
| 2 | Easy | 928 |
31.4%
|
| 3 | Difficult | 570 |
19.3%
|
| 4 | Very difficult | 321 |
10.9%
|