This study was designed to seek evidence for the validity of Stated Preference, but deliberately chose to look outside the field of transport, at: (1) Conjoint research in general market research. Opportunities for validating SP work in transport are limited and we expected there should be more scope in general market research where the range of applications and pool of experience is much broader; and (2) Experimental economics and psychology. Our interest here derived from the conviction that SP is concerned with understanding and modelling how people make decisions and choices, and SP practice will not improve without better understanding of these processes. It was found that there is little more hard evidence concerning the predictive validity of conjoint than there is for SP, but an extensive review of practice showed there are important ideas which could profitably be adapted from conjoint to improve SP practice, including: (a) internal validity checks; (b) simpler and more informative methods of analysis; and (c) a new goodness of fit test.
Samenvatting