Background
Declining response proportions in health surveys have been observed internationally over the last decades [The medium of video has many documented advantages for public health promotion compared to paper materials or spoken instructions. Video has been shown to be more effective in improving long-term knowledge retention [The aim of this study was to examine the potential of animation videos to improve response proportions and sample composition in an embedded randomized controlled trial in the Danish National Health Survey 2021 (DNHS-2021). The overall research question was whether digital invitation letters including an animation video could produce higher response proportions compared to digital letters without an animation video. The proposition was that the inclusion of animation videos in the invitation letters should increase the willingness of sample members to participate by means of increased motivation and reduced complexity, and that this would be reflected in higher response proportions. In addition, the study also examines the effect of different versions of the animation videos (targeted animations videos and a general non-targeted animation video) on response proportions across sample subgroups.