title: [Validity of epidemiological surveys with low participation rates].
abstract: BACKGROUND
  The purpose of the present study was to compare the characteristics of epidemiological survey non-respondents with the characteristics of respondents who participated by mail and phone.
  
  
  METHODS
  The study was based on data from questionnaires and registered data on socio-demographics. The Child Behavior Checklist for Ages 1-5 (CBCL/1-5) and "Experiences when answering a questionnaire" was mailed to 300 parents of children aged 18 months to five years. Parents who did not respond after a mail reminder were contacted by telephone.
  
  
  RESULTS
  A total of 138 families replied to the mail contact, 99 replied after telephone contact, and we received no response from 63 families. No statistical differences in socio-demographic characteristics were found between the three groups. No statistical differences were found concerning the total problem behaviour score of the CBCL/1-5 between mail and phone responders. Parents who participated by phone thought more frequently than mail responders that questions on the CBCL/1-5 were ethically offensive, and that their own knowledge about child well-being and behaviour was unsatisfactory, p < 0,01.
  
  
  CONCLUSIONS
  Non-participation is associated with parental attitudes towards ethical issues related to CBCL/1-5 and to poor parental knowledge about child well-being and behaviour. In spite of this, and although there was a low initial participation rate, it seems reasonable to assume that the results of child psychiatric epidemiological questionnaire surveys can be generalised.
authors.affiliation: Forskningsenheden, Det Børne- og Ungdomspsykiatriske Hus, Universitetsafdeling, DK-5000 Odense C. solvejg.kristenstensen@ouh.regionsydddanmark.dk
authors.forename: Solvejg
authors.initials: S
authors.lastname: Kristensen
authors.forename: Charlotte Maria
authors.initials: CM
authors.lastname: Jensen
authors.forename: Trine Nøhr
authors.initials: TN
authors.lastname: Winding
authors.forename: Niels
authors.initials: N
authors.lastname: Bilenberg
mesh_terms: D000328:Adult; D002648:Child; D002653:Child Behavior Disorders / Q000453:epidemiology*; D002675:Child, Preschool; D003256:Community Participation; D032984:Ethics, Research; D006801:Humans; D007223:Infant; D010290:Parents / Q000523:psychology; D011795:Surveys and Questionnaires / Q000592:standards*; D013689:Telephone