Table 1

Overview of survey characteristics

DMC3-study NetHIS
Period of researchSeptember 1998–January 1999January–December 1998
SampleTwo phase sample from population register, persons of 25 years and older, stratified by age (10 years groups) and sexTwo phase sample from population register
First contactsMail questionnaire with letter signed by handAdvance letter and after a week visit of trained interviewer with structured questionnaire programmed in laptop computer
Extra contactsOne 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
Duration30–60 minutes for completion of questionnaireInterview duration of 45 minutes on the average and 15 minutes for the questionnaire
Data collectionQuestionnaire of 28 pages with routing indicated by colours and free post return envelopeInterview and questionnaire of 12 pages (which was left behind and could be sent by free post return envelope)
ContentsGeneral characteristics (20%)General characteristics (50%)
Health characteristics (80%)Health characteristics (50%)