title: Unconditional and conditional incentives differentially improved general practitioners' participation in an online survey: randomized controlled trial.
abstract: OBJECTIVE
  To compare the impact of unconditional and conditional financial incentives on response rates among Australian general practitioners invited by mail to participate in an online survey about cancer care and to investigate possible differential response bias between incentive groups.
  
  
  METHODS
  Australian general practitioners were randomly allocated to unconditional incentive (book voucher mailed with letter of invitation), conditional incentive (book voucher mailed on completion of the online survey), or control (no incentive). Nonresponders were asked to complete a small subset of questions from the online survey.
  
  
  RESULTS
  Among 3,334 eligible general practitioners, significantly higher response rates were achieved in the unconditional group (167 of 1,101, 15%) compared with the conditional group (118 of 1,111, 11%) (P = 0.0014), and both were significantly higher than the control group (74 of 1,122, 7%; both P < 0.001). Although more positive opinions about cancer care were expressed by online responders compared with nonresponders, there was no evidence that the magnitude of difference varied by the incentive group. The incremental cost for each additional 1% increase above the control group response rate was substantially higher for the unconditional incentive group compared with the conditional incentive group.
  
  
  CONCLUSIONS
  Both unconditional and conditional financial incentives significantly increased response with no evidence of differential response bias. Although unconditional incentives had the largest effect, the conditional approach was more cost-effective.
authors.affiliation: Cancer Epidemiology and Services Research (CESR), Sydney School of Public Health, University of Sydney, Level 6 North, Lifehouse (C39Z), NSW 2006, Sydney, Australia. Electronic address: jane.young@sydney.edu.au.
authors.forename: Jane M
authors.initials: JM
authors.lastname: Young
authors.affiliation: Cancer Epidemiology and Services Research (CESR), Sydney School of Public Health, University of Sydney, Level 6 North, Lifehouse (C39Z), NSW 2006, Sydney, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: O'Halloran
authors.affiliation: Cancer Epidemiology and Services Research (CESR), Sydney School of Public Health, University of Sydney, Level 6 North, Lifehouse (C39Z), NSW 2006, Sydney, Australia.
authors.forename: Claire
authors.initials: C
authors.lastname: McAulay
authors.affiliation: Department of General Practice, University of Melbourne, 200 Berkeley St, Carlton, VIC 3053, Australia.
authors.forename: Marie
authors.initials: M
authors.lastname: Pirotta
authors.affiliation: Department of General Practice, University of Melbourne, 200 Berkeley St, Carlton, VIC 3053, Australia.
authors.forename: Kirsty
authors.initials: K
authors.lastname: Forsdike
authors.affiliation: Cancer Institute NSW, Australian Technology Park, Level 9, 8 Central Avenue, Everleigh, NSW 2015, Australia.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Stacey
authors.affiliation: Cancer Institute NSW, Australian Technology Park, Level 9, 8 Central Avenue, Everleigh, NSW 2015, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Currow
mesh_terms: D001315:Australia; D003256:Community Participation / Q000523:psychology* / Q000706:statistics & numerical data*; D055812:Community-Based Participatory Research / Q000379:methods* / Q000458:organization & administration / Q000706:statistics & numerical data; D005260:Female; D058005:General Practitioners / Q000706:statistics & numerical data*; D006306:Health Surveys / Q000379:methods* / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009042:Motivation / Q000145:classification*; D009862:Online Systems / Q000706:statistics & numerical data; D015397:Program Evaluation
keywords: General practice; Health professionals; Participation incentives; Randomized controlled trial; Response rates; Surveys