Giddy up! Can We Reduce Dropouts in a Discrete-Choice Experiment by Including an Encouraging Message? A Randomised Trial

Background: Discrete-choice experiments (DCEs) are valuable in establishing health preferences. However, their repetitive nature may cause dropouts. Aim: Does an encouraging ‘giddy-up’ message improve completion rates, data quality and respondent experience? Design: Two online DCEs in Australia: 1) breast cancer screening (women aged 40–75 y) and 2) arm therapy (stroke survivors aged >18 y). We randomised participants to see 10 to 12 choice sets continuously or with a social exchange theory–based giddy-up message halfway. Conditional binomial statistics compared dropout rates as our primary outcome. Secondary outcomes included completion time, difficulty and preference consistency. Results: From 867 screening and 333 stroke respondents, the dropout rates were 7% and 28%, respectively. Among those who completed >50% of the choice sets, there was no significant difference in dropout rates between arms (screening: 1.5% control, 0.75% giddy-up, P = 0.35; stroke: 1.7% control, 4.1% giddy-up, P = 0.30). There were no significant differences in secondary outcomes, except in the screening survey, in which the giddy-up reduced difficulty (5% vs 2%, P = 0.03) and improved understanding (18% vs 12%, P = 0.01). Conclusions: A DCE giddy-up message appears to have little impact on completion, although it may make the survey feel easier to complete. Implications: A giddy-up message is unlikely to be useful in online, adult DCEs.