title: Willingness to pay for arthritis symptom alleviation. Comparison of closed-ended questions with and without follow-up.
abstract: OBJECTIVE
  To compare two methods of measuring willingness to pay (WTP): closed-ended questions with and without follow-up.
  
  
  METHODS
  A measurement experiment based on dichotomous choice contingent valuation survey data is reported. Marginal WTP estimates for alleviation of rheumatoid arthritis symptoms resulting from treatment with a novel anti-rheumatic agent, cA2 (TNF-alpha blockade), were calculated. Monte Carlo simulations were undertaken to evaluate the methods with respect to their statistical power.
  
  
  RESULTS
  The estimated marginal WTP values using closed-ended questions with and without follow-up were DKK 637 (US $91) and DKK 1,268 (US $181), respectively. A Wilcoxon's signed-rank test showed that the difference of DKK 631 was significant. Moreover, including a follow-up question increases the precision of the result. Monte Carlo simulations showed that trade-offs between power (i.e., the probability of a correct rejection of a false null hypothesis), efficiency, and size may exist in the two models.
  
  
  CONCLUSIONS
  There was a significant difference between the WTP estimates when using closed-ended questions with and without follow-up. When choosing between the models, however, power, efficiency, and size could be used as selection criteria.
authors.affiliation: University of Southern Denmark.
authors.forename: U
authors.initials: U
authors.lastname: Slothuus
authors.forename: M L
authors.initials: ML
authors.lastname: Larsen
authors.forename: P
authors.initials: P
authors.lastname: Junker
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018501:Antirheumatic Agents / Q000191:economics / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy* / Q000503:physiopathology; D003718:Denmark; D005260:Female; D005382:Financing, Personal; D006291:Health Policy; D006801:Humans; D008297:Male; D008875:Middle Aged; D010342:Patient Acceptance of Health Care; D011795:Surveys and Questionnaires
chemical_list: D018501:Antirheumatic Agents