title: Growing cell-phone population and noncoverage bias in traditional random digit dial telephone health surveys.
abstract: OBJECTIVE
  Examine the effect of including cell-phone numbers in a traditional landline random digit dial (RDD) telephone survey.
  
  
  METHODS
  The 2007 California Health Interview Survey (CHIS).
  
  
  METHODS
  CHIS 2007 is an RDD telephone survey supplementing a landline sample in California with a sample of cell-only (CO) adults.
  
  
  METHODS
  We examined the degree of bias due to exclusion of CO populations and compared a series of demographic and health-related characteristics by telephone usage.
  
  
  RESULTS
  When adjusted for noncoverage in the landline sample through weighting, the potential noncoverage bias due to excluding CO adults in landline telephone surveys is diminished. Both CO adults and adults who have both landline and cell phones but mostly use cell phones appear different from other telephone usage groups. Controlling for demographic differences did not attenuate the significant distinctiveness of cell-mostly adults.
  
  
  CONCLUSIONS
  While careful weighting can mitigate noncoverage bias in landline telephone surveys, the rapid growth of cell-phone population and their distinctive characteristics suggest it is important to include a cell-phone sample. Moreover, the threat of noncoverage bias in telephone health survey estimates could mislead policy makers with possibly serious consequences for their ability to address important health policy issues.
authors.affiliation: Institute for Social Research, University of Michigan, 426 Thompson St., Ann Arbor, MI 48104, USA. sungheel@isr.umich.edu
authors.forename: Sunghee
authors.initials: S
authors.lastname: Lee
authors.forename: J Michael
authors.initials: JM
authors.lastname: Brick
authors.forename: E Richard
authors.initials: ER
authors.lastname: Brown
authors.forename: David
authors.initials: D
authors.lastname: Grant
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002140:California; D040421:Cell Phone / Q000706:statistics & numerical data*; D003710:Demography; D004812:Epidemiologic Methods; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D007407:Interviews as Topic / Q000379:methods; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D015983:Selection Bias; D055815:Young Adult