What is snow ball sampling ? Please differentiate different methods and techniques of sampling.

Snowball sampling is the sampling method in which research participants recruit other participants for a test or study. It is used where potential participants are hard to find. The name “snowball sampling” has been given because (in theory) once you have the ball rolling, it picks up more “snow” along the way and becomes larger and larger. Snowball sampling is a non-probability sampling method. It doesn’t have the probability involved, with say, simple random sampling (where the odds are the same for any particular participant being chosen). Rather, the researchers used their own judgment to choose participants. This sampling method involves primary data sources nominating another potential primary data sources to be used in the research. In other words, snowball sampling method is based on referrals from initial subjects to generate additional subjects. Therefore, when applying this sampling method members of the sample group are recruited via chain referral.

Snowball sampling consists of two steps:

1. Identify potential subjects in the population. Often, only one or two subjects can be found initially.
2. Ask those subjects to recruit other people (and then ask those people to recruit. Participants should be made aware that they do not have to provide any other names.

The other methods of sampling have been discussed thoroughly in the webinar presentation.