Speaker: Dr Stephane Hess (Institute for Transport Studies, University of Leeds)

Topic: Linking response quality to survey engagement: a combined random scale and latent variable approach

Abstract:
Surveys aimed at conducting choice modelling analyses routinely include questions about perceptions and attitudes. While researchers have occasionally included responses to such questions in their models in a deterministic fashion, it is well known that this can have a biasing influence on parameter estimates. This has led to a growing popularity for latent variable approaches that jointly model the response to stated choice tasks and attitudinal questions. Such hybrid frameworks have proved a fruitful approach for explaining differences across individual respondents in sensitivities. At the same time, a separate stream of research has started to openly question the nature of the taste heterogeneity retrieved in Mixed Logit analyses, showing that at least part of the heterogeneity retrieved in such models is in fact scale heterogeneity, i.e. variation in absolute rather than relative sensitivities. In the present paper, we combine these two approaches. Specifically, we hypothesise that differences across respondents in survey engagement, understanding or attention result in differences in response quality, expressed as scale heterogeneity. We model this through a random scale approach that interacts with a latent variable model. Here, we find clear evidence that respondents who indicate a higher level of understanding and engagement with the survey are more likely to have higher scale. Furthermore, allowing for this additional model complexity leads to noticeable differences in the retrieved heterogeneity patterns.

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