| Value | Category | Cases | |
|---|---|---|---|
| 1 | No difficulty | 684 |
98.4%
|
| 2 | Some difficulty | 7 |
1%
|
| 3 | A lot of difficulty | 1 |
0.1%
|
| 4 | Cannot see at all | 3 |
0.4%
|
| 9 | Missing | 0 |
0%
|
| Sysmiss | 428 |