How to Survey Hard-to-Reach Populations: A Practical Guide to App-Based Respondent-Driven Sampling

Abstract

Target populations that are hidden, elusive, and marginalized are usually hard-to-reach for (sur-vey)research. To overcome the difficulties in reaching such target groups, we propose an inno-vativedigital adaption of respondent-driven sampling (RDS). This paper introduces a novel fully app-basedRDS approach for collecting high-quality data on particularly hard-to-reach target groups. Based onspecific examples from our own research with rejected asylum seekers from West Africa living inGermany, we offer practical guidance along four steps of implementing an RDS smartphone app,from getting to know one’s target group, over the formative assessment, app development, and datacollection and analysis. Thereby, we reflect practical, technical, and ethical challenges that need tobe considered. Proposing feasible solutions for others to imple-ment this innovative approach, weadvance the methods for researching particularly hard-to-reach groups.

Keywords: Respondent-driven sampling, non-probability sampling, smartphone survey, hard-to-reach populations, irregular migrants