A review of quality issues associated with studying hard-to-survey populations

Some populations/groups are defined as hard to survey (H2S) in the research literature because of difficulty sampling the population, accessing the population, contacting members of the population, persuading them to participate, and interviewing group members (see Tourangeau, Chapter 1 in this volume). Reviewing the literature on populations referred to as "hard to survey" indicates the types of studies undertaken with these populations, the survey error challenges, and the methodological solutions used by researchers who study such populations. The H2S literature, however, does have limitations and research gaps exist.