Overview of survey characteristics
| DMC3-study | NetHIS | ||
| Period of research | September 1998–January 1999 | January–December 1998 | |
| Sample | Two phase sample from population register, persons of 25 years and older, stratified by age (10 years groups) and sex | Two phase sample from population register | |
| First contacts | Mail questionnaire with letter signed by hand | Advance letter and after a week visit of trained interviewer with structured questionnaire programmed in laptop computer | |
| Extra contacts | One reminder after three weeks (letter), second reminder after six weeks (response card, telephone or questionnaire) | A maximum of three home visits on different times, one reminder (letter) for the questionnaire | |
| Duration | 30–60 minutes for completion of questionnaire | Interview duration of 45 minutes on the average and 15 minutes for the questionnaire | |
| Data collection | Questionnaire of 28 pages with routing indicated by colours and free post return envelope | Interview and questionnaire of 12 pages (which was left behind and could be sent by free post return envelope) | |
| Contents | General characteristics (20%) | General characteristics (50%) | |
| Health characteristics (80%) | Health characteristics (50%) | ||