title: A two-phase sampling survey for nonresponse and its paradata to correct nonresponse bias in a health surveillance survey.
abstract: BACKGROUND
  The decline in participation rates in surveys, including epidemiological surveillance surveys, has become a real concern since it may increase nonresponse bias. The aim of this study is to estimate the contribution of a complementary survey among a subsample of nonrespondents, and the additional contribution of paradata in correcting for nonresponse bias in an occupational health surveillance survey.
  
  
  METHODS
  In 2010, 10,000 workers were randomly selected and sent a postal questionnaire. Sociodemographic data were available for the whole sample. After data collection of the questionnaires, a complementary survey among a random subsample of 500 nonrespondents was performed using a questionnaire administered by an interviewer. Paradata were collected for the complete subsample of the complementary survey. Nonresponse bias in the initial sample and in the combined samples were assessed using variables from administrative databases available for the whole sample, not subject to differential measurement errors. Corrected prevalences by reweighting technique were estimated by first using the initial survey alone and then the initial and complementary surveys combined, under several assumptions regarding the missing data process. Results were compared by computing relative errors.
  
  
  RESULTS
  The response rates of the initial and complementary surveys were 23.6% and 62.6%, respectively. For the initial and the combined surveys, the relative errors decreased after correction for nonresponse on sociodemographic variables. For the combined surveys without paradata, relative errors decreased compared with the initial survey. The contribution of the paradata was weak.
  
  
  CONCLUSIONS
  When a complex descriptive survey has a low response rate, a short complementary survey among nonrespondents with a protocol which aims to maximize the response rates, is useful. The contribution of sociodemographic variables in correcting for nonresponse bias is important whereas the additional contribution of paradata in correcting for nonresponse bias is questionable.
authors.affiliation: Direction santé travail, Santé publique France, 94415 Saint-Maurice, France; UMS 011, Inserm-UVSQ, unité « Cohortes épidémiologiques en population », 94807 Villejuif cedex, France. Electronic address: gaelle.santin@inserm.fr.
authors.forename: G
authors.initials: G
authors.lastname: Santin
authors.affiliation: Direction santé travail, Santé publique France, 94415 Saint-Maurice, France.
authors.forename: L
authors.initials: L
authors.lastname: Bénézet
authors.affiliation: Direction santé travail, Santé publique France, 94415 Saint-Maurice, France.
authors.forename: B
authors.initials: B
authors.lastname: Geoffroy-Perez
authors.affiliation: Inserm, CESP centre de recherche en épidémiologie et santé des populations, équipe 4 : VIH/Pédiatrie, 94270 Le Kremlin-Bicêtre, France.
authors.forename: J
authors.initials: J
authors.lastname: Bouyer
authors.affiliation: UMS 011, Inserm-UVSQ, unité « Cohortes épidémiologiques en population », 94807 Villejuif cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Guéguen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015982:Bias; D003625:Data Collection / Q000379:methods*; D005602:France / Q000453:epidemiology; D019538:Health Care Surveys / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D016272:Occupational Health / Q000706:statistics & numerical data; D010865:Pilot Projects; D011159:Population Surveillance / Q000379:methods*; D011634:Public Health / Q000379:methods / Q000592:standards; D012494:Sampling Studies; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Biais de sélection; Enquête de santé publique; Enquête en deux phases pour non-réponse; Non-réponse totale; Paradata; Paradonnées; Public health survey; Selection bias; Two-phase sampling for nonresponse; Unit nonresponse