Using qualitative methods to validate a stated preference survey for evaluating health services, CHERE Discussion Paper No 47

This study used a qualitative approach to assess parents? opinions of a self-completed stated preference discrete choice modelling (SPDCM) questionnaire for assessing the uptake of a new childhood vaccination against chickenpox. The aim was to assess the way parents understood and used the technical information provided, the factors they deemed important to decisions about childhood immunisation and the extent to which these were consistent with the models produced by analysis of the questionnaire data. Following completion of the SPDCM questionnaire, 34 respondents participated in a semi-structured interview by telephone. Interview transcripts were analysed using content analysis. Comparisons were then made with the SPDCM questionnaire results. The technical information used to describe the program attributes appeared to be used appropriately by respondents, although their explanations indicated that their understanding did not always come from the questionnaire information. Only one respondent appeared to misunderstand the stated preference task, and a small number thought that the complexity and length should be reduced. The group results for the questionnaire data were supported by the qualitative study, with the notable features of the model being reflected in the views commonly expressed about the immunisation decision. Generally, the study provides support for the potential usefulness of the SPDCM methodology for predicting the uptake of a new vaccination.