| Value | Category | Cases | |
|---|---|---|---|
| -99 | 1 | 
                                    
                                    0.7%
                                 | |
| 1 | Not effective at all | 3 | 
                                    
                                    2.2%
                                 | 
| 2 | 1 | 
                                    
                                    0.7%
                                 | |
| 3 | 6 | 
                                    
                                    4.5%
                                 | |
| 4 | 2 | 
                                    
                                    1.5%
                                 | |
| 5 | 21 | 
                                    
                                    15.7%
                                 | |
| 6 | 14 | 
                                    
                                    10.4%
                                 | |
| 7 | 18 | 
                                    
                                    13.4%
                                 | |
| 8 | 16 | 
                                    
                                    11.9%
                                 | |
| 9 | 9 | 
                                    
                                    6.7%
                                 | |
| 10 | Very effective | 5 | 
                                    
                                    3.7%
                                 | 
| 11 | Don't know | 38 | 
                                    
                                    28.4%
                                 |