title: A randomised controlled trial to determine the effect on response of including a lottery incentive in health surveys [ISRCTN32203485].
abstract: BACKGROUND
  Postal questionnaires are an economical and simple method of data collection for research purposes but are subject to non-response bias. Several studies have explored the effect of monetary and non-monetary incentives on response. Recent meta-analyses conclude that financial incentives are an effective way of increasing response rates. However, large surveys rarely have the resources to reward individual participants. Three previous papers report on the effectiveness of lottery incentives with contradictory results. This study aimed to determine the effect of including a lottery-style incentive on response rates to a postal health survey.
  
  
  METHODS
  Randomised controlled trial.
  
  
  METHODS
  North and West Birmingham. 8,645 patients aged 18 or over randomly selected from registers of eight general practices (family physician practices).
  
  
  METHODS
  Inclusion of a flyer and letter with a health questionnaire informing patients that returned questionnaires would be entered into a lottery-style draw for pound 100 of gift vouchers.
  
  
  METHODS
  Health questionnaire accompanied only by standard letter of explanation.
  
  
  METHODS
  Response rate and completion rate to questionnaire.
  
  
  RESULTS
  5,209 individuals responded with identical rates in both groups (62.1%). Practice, patient age, sex and Townsend score (a postcode based deprivation measure) were identified as predictive of response, with higher response related to older age, being female and living in an area with a lower Townsend score (less deprived).
  
  
  CONCLUSIONS
  This RCT, using a large community based sample, found that the offer of entry into a lottery style draw for pound 100 of High Street vouchers has no effect on response rates to a postal health questionnaire.
authors.affiliation: Dept. Primary Care and General Practice, Division of Primary Care, Public and Occupational Health, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. l.m.roberts@bham.ac.uk <l.m.roberts@bham.ac.uk>
authors.forename: L M
authors.initials: LM
authors.lastname: Roberts
authors.forename: S
authors.initials: S
authors.lastname: Wilson
authors.forename: A
authors.initials: A
authors.lastname: Roalfe
authors.forename: P
authors.initials: P
authors.lastname: Bridge
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015709:Correspondence as Topic; D004739:England; D005194:Family Practice; D005260:Female; D005715:Gambling; D006306:Health Surveys; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009042:Motivation; D018579:Patient Selection; D011177:Postal Service / Q000706:statistics & numerical data*; D011204:Poverty Areas; D015995:Prevalence; D012201:Reward; D011795:Surveys and Questionnaires / Q000191:economics / Q000706:statistics & numerical data*