When the population is hard to reach, the sampling strategy that relies on participants referring others is called

• A. Purposive sampling
• B. Convenience sampling
• C. Quota sampling
• D. Snowball sampling

Answer: (D)

Snowball sampling is used when the population is hard to reach. Start with a few initial participants who fit the criteria, then ask each one to refer others they know who also fit, and those new participants refer more people, creating a chain like a rolling snowball. This method relies on social networks to locate individuals who are difficult to find through other means, making it practical for hidden, stigmatized, or newly identified groups and for exploratory work.

Because the sample grows through referrals, it isn’t random and can overrepresent connected individuals or clusters within the network, which limits how well findings generalize to the broader population. This approach contrasts with purposive sampling (selecting cases for specific reasons without relying on referrals), convenience sampling (relying on who is easiest to reach), and quota sampling (ensuring predefined subgroups)—none of which use the chain-referral process.