| Value | Category | Cases | |
|---|---|---|---|
| 0 | not difficult at all | 1246 | 
                                    
                                    8.3%
                                 | 
| 1 | 543 | 
                                    
                                    3.6%
                                 | |
| 2 | 1090 | 
                                    
                                    7.3%
                                 | |
| 3 | 764 | 
                                    
                                    5.1%
                                 | |
| 4 | 480 | 
                                    
                                    3.2%
                                 | |
| 5 | 673 | 
                                    
                                    4.5%
                                 | |
| 6 | 465 | 
                                    
                                    3.1%
                                 | |
| 7 | 417 | 
                                    
                                    2.8%
                                 | |
| 8 | 299 | 
                                    
                                    2%
                                 | |
| 9 | 78 | 
                                    
                                    0.5%
                                 | |
| 10 | extremely difficult | 69 | 
                                    
                                    0.5%
                                 | 
| -8 | other error | 0 | 
                                    
                                    0%
                                 | 
| -7 | filter error | 0 | 
                                    
                                    0%
                                 | 
| -3 | inapplicable | 8826 | 
                                    
                                    59%
                                 | 
| -2 | no answer | 8 | 
                                    
                                    0.1%
                                 | 
| -1 | does not know | 3 | 
                                    
                                    0%
                                 |