title: [Efforts to increase the response to mailed questionnaires].
abstract: BACKGROUND
  Great effort should be made to ensure that as many subjects as possible reply when using mailed questionnaires. It has been shown that including a monetary reward or sending a short form increases the number of replies. The purpose of the study was to determine whether this is true also in Scandinavia.
  
  
  METHODS
  Questionnaires were sent to 200 women and 200 men in each age decade of 20-29 years and older. Totally, 2,000 long and 800 short questionnaires were mailed - 200 letters included 50 NOK (Norwegian kroner), 500 letters included 10 NOK, and 1,000 letters included 1 NOK. At the time of mailing 5 NOK was worth approximately 1 USD. The remainder served as controls. Block randomization ensured an even distribution of the various rewards and long and short forms in each age decade and sex.
  
  
  RESULTS
  After 11 weeks 59% had returned the short form and 54% the long form (p = 0.03). Replies were received from 54% of the control subjects, from 53% of subjects who had received 1 NOK, from 58% of subjects who had received 10 NOK, and from 74% of subjects who had received 50 NOK (p < 0.001).
  
  
  CONCLUSIONS
  A short form is returned statistically significantly more often than a long form, but the difference is only moderate. A monetary reward increases the rate of reply considerably also in Scandinavia. The sum sent must be fairly high to have effect.
authors.affiliation: Ortopedisk avdeling, St. Olavs Hospital, 7006 Trondheim, Norge. vilh.finsen@ntnu.no
authors.forename: Vilhjalmur
authors.initials: V
authors.lastname: Finsen
mesh_terms: D000328:Adult; D003625:Data Collection / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D009042:Motivation; D009664:Norway; D011177:Postal Service; D012201:Reward; D011795:Surveys and Questionnaires / Q000191:economics; D055815:Young Adult