Grutters Janneke P C, Anteunis Lucien J C, Chenault Michelene N, Joore Manuela A
Department of Clinical Epidemiology and Medical Technology Assessment, University Hospital Maastricht, Maastricht, The Netherlands.
J Eval Clin Pract. 2009 Feb;15(1):91-6. doi: 10.1111/j.1365-2753.2008.00959.x.
RATIONALE & OBJECTIVES: Different question formats elicit different willingness-to-pay (WTP) results, but there is no consensus on which method elicits the most valid WTP. In spite of the methodological controversies, WTP is a potentially valuable tool in health economics to value health services. Our general objective was to provide additional evidence on the validity of two WTP elicitation formats: the open-ended question and the payment scale.
We elicited WTP for a hearing aid among hearing aid users (n = 108), using both a payment scale and an open-ended question. We compared the results from both formats. We tested criterion validity by comparing both formats with the actual out-of-pocket payment. Construct validity was tested by examining whether WTP was consistent with positive income elasticity.
The WTP results elicited with the payment scale and open-ended question were not statistically significantly different. Both formats showed good criterion validity, although the open-ended question showed a stronger association with the actual out-of-pocket payment. The open-ended format showed better construct validity, as it was influenced by family income.
The results of the present study showed that the open-ended question was more valid than the payment scale question. We, therefore, recommend that in future WTP studies on hearing aids the open-ended question is used to directly elicit WTP values. The same recommendation may apply to other studies where respondents are familiar with costs or payments for the intervention under evaluation.
不同的问题形式会得出不同的支付意愿（WTP）结果，但对于哪种方法能得出最有效的支付意愿，尚无共识。尽管存在方法上的争议，但支付意愿在卫生经济学中是评估卫生服务价值的一个潜在有价值的工具。我们的总体目标是为两种支付意愿诱导形式的有效性提供更多证据：开放式问题和支付量表。
我们使用支付量表和开放式问题，对助听器使用者（n = 108）的助听器支付意愿进行了诱导。我们比较了两种形式的结果。通过将两种形式与实际自付费用进行比较来测试标准效度。通过检查支付意愿是否与正收入弹性一致来测试结构效度。
支付量表和开放式问题得出的支付意愿结果在统计学上没有显著差异。两种形式都显示出良好的标准效度，尽管开放式问题与实际自付费用的关联更强。开放式形式显示出更好的结构效度，因为它受家庭收入的影响。
本研究结果表明，开放式问题比支付量表问题更有效。因此，我们建议在未来关于助听器的支付意愿研究中，使用开放式问题直接诱导支付意愿值。同样的建议可能适用于其他研究，即受访者熟悉所评估干预措施的成本或支付情况的研究。
