Hypothetical bias in stated choice experiments: Part II. Conceptualisation of external validity, sources and explanations of bias and effectiveness of mitigation methods

Applications of discrete choice experiments in COVID-19 research: Disparity in survey qualities between health and transport fields

“…Transport researchers have essentially developed and adopted this method as a mean of creating contextual familiarity for survey respondents and thereby reducing hypothetical bias. A previous study also noted the unique popularity of this technique in transport, compared to all other areas of applied economics ( Haghani et al, 2021c ). The said observation was also reflected in the current study in pandemic-related choice experiments where three out of ten transport surveys adopted this technique, whereas, similar to a broader trend, this method was absent in health.…”

“…The potential presence of hypothetical bias and its effect on findings and predictions of discrete choice experiments have been documented in previous work ( Haghani et al, 2021b ). In Haghani et al (2021c) , ten major factors were discussed that could potentially engender such bias in choice experiments. Their role varies across contexts and applications of choice experiments.…”

“…In other words, this observation could be flagging a potential broader issue, and if further future studies confirm that this is the case (i.e., that this is not specific to pandemic-related studies per se), then it will be recommendable that transport researchers need to adopt existing guidelines that are common in health or that they develop specific guidelines tailored to specific choice problems typically studied in transport. In a recent study looking at effectiveness of hypothetical bias mitigation methods, it was observed that health economics significantly pay more attention to the issue of hypothetical bias mitigation compared transport researchers ( Haghani et al, 2021c ). Therefore, we cannot rule out the possibility that the observations of the current study are also reflective of a broader difference in experimental design culture across these two sectors, a problem that warrants attention.…”

“…After screening, a total of N = 43 articles met the inclusion criteria. Consistent with Haghani et al (2021b) and Haghani et al (2021c) , the articles were further classified to the subdomains of health, transport, environmental and marketing/consumer studies. This determination was made based on the nature and topic of the choice experiment reported in the paper.…”

Open vs closed-ended questions in attitudinal surveys – Comparing, combining, and interpreting using natural language processing

“…Although there has been debate on the prevalence and importance of analyzing hypothetical bias, it is an area that still requires considerable attention, particularly in transportation studies that involve large public investments (Haghani et al, 2021a). Haghani et al (2021b) discuss the different methods researchers use to mitigate hypothetical bias. We believe this might be more relevant for online surveys, particularly voice-based surveys.…”