Dr. Jackson is a personality psychologist who is interested in studying the characteristics of people who report being abducted by UFOs. She finds several people in a support group to research and asks them if they can provide the names and contact information of other people who have also been abducted. Upon contacting these new participants, she asks them to refer her to even more people they may know who have been abducted. This is an example of what kind of sampling?
1. Self-selection sampling2. Snowball sampling3. Purposive sampling4. Convenience sampling

Snowball sampling: The snowball sampling refers to the sampling method in which research participants recommends a few other participants for the purpose of study or research. The snowball sampling method is being used when the potential participants for a study or research are hard to find.

Example: In various interview procedures, the snowball technique can be used to find or discover the hard-to-reach population.

Advantage: Cost-efficient, simple, and cheap process.

In the question above, Dr. Jackson is using snowball sampling.