In which sampling method do existing participants help to recruit new participants?

The correct answer is snowball sampling, which is a unique method particularly useful in research where participants are hard to reach or belong to specific networks. In this approach, existing participants leverage their social connections to recruit new participants. As the name suggests, the sample size can increase like a snowball rolling down a hill; as each participant refers others, the sample expands.

This method is beneficial for accessing populations that may be hidden or difficult to engage through traditional sampling methods, such as certain marginalized groups. It capitalizes on the trust and relationships that individuals already have within their communities, creating an opportunity to gather data that might otherwise be inaccessible.

Other sampling methods, such as stratified sampling or cluster sampling, focus on random selection from divided groups or clusters and do not involve existing participants in the recruitment process. Systematic sampling follows a fixed, predetermined interval for selection and is also not reliant on participant referrals. In contrast, snowball sampling is characterized by its reliance on the existing study population to grow and diversify the sample, thus making it distinct and effective for certain types of research.