| Value | Category | 
                                    
                    
                        | 0 |  | 
                                    
                    
                        | 1 | Easy | 
                                    
                    
                        | 2 | Relatively easy | 
                                    
                    
                        | 3 | Somewhat difficult | 
                                    
                    
                        | 4 | Difficult | 
                                    
                    
                        | 5 | Can not | 
                                    
                    
                        | 6 | Do not do | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.