| Value | Category | Cases | |
|---|---|---|---|
| 1 | Not effective at all | 2 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             | 
                                                        
                    
| 2 | 5 | 
                                                                 
                                    
                                    2.3%
                                 
                                                             | 
                                                        
                    |
| 3 | 7 | 
                                                                 
                                    
                                    3.2%
                                 
                                                             | 
                                                        
                    |
| 4 | 3 | 
                                                                 
                                    
                                    1.4%
                                 
                                                             | 
                                                        
                    |
| 5 | 21 | 
                                                                 
                                    
                                    9.5%
                                 
                                                             | 
                                                        
                    |
| 6 | 27 | 
                                                                 
                                    
                                    12.3%
                                 
                                                             | 
                                                        
                    |
| 7 | 35 | 
                                                                 
                                    
                                    15.9%
                                 
                                                             | 
                                                        
                    |
| 8 | 39 | 
                                                                 
                                    
                                    17.7%
                                 
                                                             | 
                                                        
                    |
| 9 | 21 | 
                                                                 
                                    
                                    9.5%
                                 
                                                             | 
                                                        
                    |
| 10 | Very effective | 23 | 
                                                                 
                                    
                                    10.5%
                                 
                                                             | 
                                                        
                    
| 11 | Don't know | 37 | 
                                                                 
                                    
                                    16.8%
                                 
                                                             |