| Value | Category | Cases | |
|---|---|---|---|
| -99 | 2 | 
                                    
                                    1.5%
                                 | |
| 1 | Not effective at all | 4 | 
                                    
                                    3%
                                 | 
| 2 | 2 | 
                                    
                                    1.5%
                                 | |
| 3 | 5 | 
                                    
                                    3.7%
                                 | |
| 4 | 5 | 
                                    
                                    3.7%
                                 | |
| 5 | 13 | 
                                    
                                    9.7%
                                 | |
| 6 | 22 | 
                                    
                                    16.4%
                                 | |
| 7 | 24 | 
                                    
                                    17.9%
                                 | |
| 8 | 16 | 
                                    
                                    11.9%
                                 | |
| 9 | 4 | 
                                    
                                    3%
                                 | |
| 10 | Very effective | 9 | 
                                    
                                    6.7%
                                 | 
| 11 | Don't know | 28 | 
                                    
                                    20.9%
                                 |