| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1. Per month | 31 | 
                                                                 
                                    
                                    70.5%
                                 
                                                             | 
                                                        
                    
| 2 | 2. Per semester | 3 | 
                                                                 
                                    
                                    6.8%
                                 
                                                             | 
                                                        
                    
| 3 | 3. Per year | 10 | 
                                                                 
                                    
                                    22.7%
                                 
                                                             | 
                                                        
                    
| 5 | 5. Others | 0 | 
                                                                 
                                    
                                    0%
                                 
                                                             | 
                                                        
                    
| 6 | 6. None | 0 | 
                                                                 
                                    
                                    0%
                                 
                                                             | 
                                                        
                    
| 9 | 9. Missing | 0 | 
                                                                 
                                    
                                    0%
                                 
                                                             | 
                                                        
                    
| Sysmiss | 188 |