title: Does anonymity increase response rate in postal questionnaire surveys about sensitive subjects? A randomised trial.
abstract: OBJECTIVE
  The aim of the study was to determine whether complete anonymity improves the response rates to a postal questionnaire.
  
  
  METHODS
  The study derived from a series of postal surveys on AIDS knowledge conducted on six different dates in 1986 and 1987. The sample was randomly divided into two, each group being sent the same questionnaire. One group was informed that the replies were anonymous, the other that they were not. The latter were sent reminders.
  
  
  METHODS
  Recipients of the questionnaires were drawn from the Southampton electoral rolls.
  
  
  METHODS
  300 people in each survey (total 1800) were sent questionnaires, representing on each occasion a different 1:500 systematic sample.
  
  
  RESULTS
  Response rate was 49% for the anonymous questionnaires and 51% for the numbered questionnaires. Reminders boosted the response in the numbered group to 72%.
  
  
  CONCLUSIONS
  There is no evidence that anonymity improves response to postal questionnaires, but the use of reminders may do so.
authors.affiliation: University of Southampton, United Kingdom.
authors.forename: M J
authors.initials: MJ
authors.lastname: Campbell
authors.forename: W E
authors.initials: WE
authors.lastname: Waters
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000523:psychology*; D004739:England; D006801:Humans; D011177:Postal Service; D011897:Random Allocation; D011795:Surveys and Questionnaires