Technique in which research participants identify other potential participants and particularly useful in identifying participants from a difficult to find population, such types of method of sampling is referred as:

Purposive sampling.

Snowball sampling.

Convenience sampling.

Quota sampling.

The answer is Snowball Sampling.

Reasons-

Snowball Sampling is used for a test or study where the research participants are recruited by other potential participants. The reason for this is that, a lot of times in our research for ethically complicated matters, the participant might not be comfortable to disclose their names. However, they would readily suggest another name for the same whose confidentiality is promised to be maintained.

The ethically complicated matters of research might include drug abuse, robbery, sexual intercourses, cheating in an exam, etc. which the participant is hesitant to speak under his/her own name as that would spill beans about their own selves.

It is called snowball sampling as once the ball has started rolling, it picks up, more snow along the way and starts to become bigger and bigger on its own.Snowball sampling is a non-probability sampling method where judgement of researchers are used to choose their participants. So, first a potential participant is identified, who is then asked to introduce us to another potential participant who can be researched.