A venue-based method for sampling hard-to-reach populations

Constructing scientifically sound samples of hard-to-reach populations, als o known as hidden populations, is a challenge for many research projects. T raditional sample survey methods, such as random sampling from telephone or mailing lists, can yield low numbers of eligible respondents while non-pro bability sampling introduces unknown biases. The authors describe a venue-based application of time-space sampling (TSS) that addresses the challenges of accessing hard-to-reach populations. The method entails identifying days and times when the target population gather s at specific venues, constructing a sampling frame of venue, day-time unit s (VDTs), randomly selecting and visiting VDTs (the primary sampling units) , and systematically intercepting and collecting information from consentin g members of the target population. This allows researchers to construct a sample with known properties, make statistical inference to the larger popu lation of venue visitors, and theorize about the introduction of biases tha t may limit generalization of results to the target population. The authors describe their use of TSS in the ongoing Community Intervention Trial for Youth (CITY) project to generate a systematic sample of young me n who have sex with men, The project is an ongoing community level HIV prev ention intervention trial funded by the Centers for Disease Control and Pre vention. The TSS method is reproducible and can be adapted to hard-to-reach populati ons in other situations, environments, and cultures.