Which sampling technique relies on inviting people to participate through advertising?

Volunteer sampling is characterized by individuals self-selecting to participate in a study, often in response to advertisements or public requests for participants. This method depends on the willingness of individuals to come forward and contribute to the research, which can be effective in gathering a diverse array of participants, depending on the appeal of the advertisement and the demographic targeted. Since the sample is composed of those who choose to engage, it can reflect certain biases based on who saw the advertisement and decided to volunteer, yet it is a practical technique when access to a broader population is limited.

In contrast, random sampling involves selecting participants from the larger population entirely by chance, ensuring every individual has an equal opportunity of being chosen, and does not rely on voluntary participation. Systematic sampling follows a structured method of selection based on a fixed interval; it does not involve advertising for participants. Stratified sampling divides the population into subgroups to ensure representation across specific characteristics but also does not involve a voluntary response mechanism. Thus, volunteer sampling is the only option that directly involves inviting individuals to participate through advertisements.