Does Mode Matter? Impact of Survey Administration Mode on Health-Related Contingent Valuation: Face-to-Face and Telephone Interviews

OBJECTIVES: Although face-to-face interviews were the most common contingent valuation (CV) data collection mode, there has been a shift toward electronic surveys (telephone or online surveys). This study aimed to investigate whether the choice of CV administration mode (face-to-face vs. telephone) results in measurement effects in terms of quantifying the willingness to pay for one additional quality adjusted life year (WTP/Q).

METHODS: The data was drawn from the population survey of WTP/Q. Propensity score matching was used to make the samples comparable. The share of zero, protest zero, irrational values and mean WTP/Q of two modes were first compared via Chi-squared tests and parametric t-test. We then composed a three-part model (multinomial logit, probit and generalized linear model) to further determine the difference between response patterns including variables related to demographic, health states, and hypothetical scenarios.

RESULTS: After propensity score matching, the final sample sizes for the face-to-face and telephone interviews were 241 and 854, respectively. Chi-squared tests and parametric t-tests found that face-to-face interviews were associated with a greater prevalence of zero responses and lower WTP/Q. In addition, analysis via a multinomial logit model revealed that the survey mode did not significantly affect the proportion of protest zeros and irrational values, P = 0.401. In contrast, probit modeling indicated that face-to-face surveys were significantly associated with an increased frequency of zero responses (P = 0.004). In addition, the generalized linear model showed a statistically significantly higher WTP/Q for the telephone survey (mean = 121,000 RMB) compared to the face-to-face interviews (mean = 92,900 RMB), P = 0.001.

CONCLUSIONS: The research elucidates that the mode of survey administration exerts a significant influence on the outcomes of health-related contingent valuation, particularly concerning zero responses and WTP/Q. It is imperative for future studies to consider the substantial impact of survey methodology on their findings.