An exploratory analysis of the effect of numbers of choice sets in designed choice experiments: An airline choice application

Stated choice (SC) experiments are increasingly adopted as the empirical source of information on how individuals respond to current and potential travel contexts. The accumulated experience with SC data has been heavily conditioned on analyst prejudices about the acceptable complexity of the data collection instrument, especially the number of profiles (or treatments) given to each sampled individual (and the number of attributes and alternatives to be processed). It is not uncommon for analysts to impose very stringent limitations on the complexity of an SC experiment. A review of the literature suggests that very little is known about the basis for rejecting complex designs or accepting simple designs. In this paper, we develop a complex design as the basis for an SC study, producing a fractional factorial of 32 rows. However, we then truncate the fraction by administering 4, 8, 16, 24 and 32 profiles to a sample of individuals in Australia and New Zealand faced with the decision to fly (or not to fly) between Australia and New Zealand by alternative airlines and fare regimes. Statistical comparisons of elasticities (an appropriate behavioural basis for comparisons) suggest that the empirical gains within the context of a linear specification of the utility expression associated with each alternative in a discrete choice model may be quite marginal.