Snowball Sampling

Snowball sampling is the colorful name or technique of building up a list or a sample of a special population. Some recent authors have referred to snowball sampling as a chain referral sampling. It has achieved increased use in recent years in situations where respondents are difficult to identity and are best located by using in initial set of its members or informants through referral network approach (Kish, 1961). For example, consider the selection of beggars for which no frame is available. This can be best done by asking an initial group of beggars to supply the name of other beggars they come across. Selection of mosque Imams or the sex workers also can be made following this network approach, since members of this population may well know each other particularly in small areas.


Snowball sampling is a non-probability sampling in which persons initially chosen for the sample are used as informants to locate other persons having necessary characteristics making them eligible for the sample through referral network.

Although snowball sampling is generally considered non-probability sampling, strategies have been developed to draw snowball sampling through probabilistic approach, which allows compilations of sampling errors, and use statistical test of significance. If one wishes, the snowball sample to be probabilistic, one should sample randomly within each stage.

Snowball sampling, whether probabilistic or non-probabilistic, is conducted in stages. In the first, a few persons processing the requisite characteristic are identified and interviewed in the third stages and so on. The term snowball stems from the analogy of a snowball, which begins small but becomes bigger and bigger as it falls downhill.

Snowball sampling has been particularly used to study drug culture, heroin addiction, teenage gang activities, community relations and other issues where respondents may not be visible or are difficult to identify and contact.