title: Does length of questionnaire matter? A randomised trial of response rates to a mailed questionnaire.
abstract: OBJECTIVE
  To assess whether length of questionnaire affects response rates.
  
  
  METHODS
  A quasi-randomised trial of women aged 70 years and over in a general practice in England. Three questionnaires of different lengths: a clinical questionnaire (four pages); the same questionnaire plus the EuroQol (five pages); the same questionnaire plus the SF-12 (seven pages). The impact of length on the proportion of returned questionnaires and item completion rates was assessed.
  
  
  RESULTS
  In total, 847 questionnaires were mailed; response rates were 49%, 49% and 40% to the short, medium and long questionnaires, respectively. This difference was statistically significant when the short questionnaire was compared against the longest instrument (9% difference; 95% confidence interval (CI) of difference = 0.3% to 16.6%). Item completion rates for the clinical questionnaire did not differ. Respondents did not differ in age or self-reported health status between the three groups.
  
  
  CONCLUSIONS
  Increasing the length of a questionnaire from five to seven pages reduces response rates from women aged 70 years and over. However, lengthening a questionnaire does not seem to affect the quality of responses to questions near the front of the questionnaire.
authors.affiliation: Department of Health Studies, University of York, UK.
authors.forename: C
authors.initials: C
authors.lastname: Iglesias
authors.forename: D
authors.initials: D
authors.lastname: Torgerson
mesh_terms: D000368:Aged; D004739:England / Q000453:epidemiology; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D010024:Osteoporosis / Q000150:complications; D010358:Patient Participation; D011897:Random Allocation; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires / Q000592:standards*