| Value | Category | Cases | |
|---|---|---|---|
| 1 | No difficulty | 8426 |
85.8%
|
| 2 | Some difficulty | 1181 |
12%
|
| 3 | A lot of difficulty | 202 |
2.1%
|
| 4 | Cannot see at all | 11 |
0.1%
|
| Sysmiss | 3679 |