| Value | Category | 
                                    
                    
                        | 0 | no | 
                                    
                    
                        | 1 | yes | 
                                    
                    
                        | 2 | No need, complete obs | 
                                    
                    
                        | 9999 | Not in the psy module or invalid obs | 
                                    
                    
                        | 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.