Snowball sampling

In sociology and statistics research, snowball sampling (or chain sampling, chain-referral sampling, referral sampling) is a nonprobability sampling technique where existing study subjects recruit future subjects from among their acquaintances. Thus the sample group is said to grow like a rolling snowball. As the sample builds up, enough data are gathered to be useful for research. This sampling technique is often used in hidden populations, such as drug users or sex workers, which are difficult for researchers to access.As sample members are not selected from a sampling frame, snowball samples are subject to numerous biases. For example, people who have many friends are more likely to be recruited into the sample. When virtual social networks are used, then this technique is called virtual snowball sampling. In sociology and statistics research, snowball sampling (or chain sampling, chain-referral sampling, referral sampling) is a nonprobability sampling technique where existing study subjects recruit future subjects from among their acquaintances. Thus the sample group is said to grow like a rolling snowball. As the sample builds up, enough data are gathered to be useful for research. This sampling technique is often used in hidden populations, such as drug users or sex workers, which are difficult for researchers to access.As sample members are not selected from a sampling frame, snowball samples are subject to numerous biases. For example, people who have many friends are more likely to be recruited into the sample. When virtual social networks are used, then this technique is called virtual snowball sampling. It was widely believed that it was impossible to make unbiased estimates from snowball samples, but a variation of snowball sampling called respondent-driven samplinghas been shown to allow researchers to make asymptotically unbiased estimates from snowball samples under certain conditions. Snowball sampling and respondent-driven sampling also allows researchers to make estimates about the social network connecting the hidden population. Snowball sampling uses a small pool of initial informants to nominate, through their social networks, other participants who meet the eligibility criteria and could potentially contribute to a specific study. The term 'snowball sampling' reflects an analogy to a snowball increasing in size as it rolls downhill. The participants are likely to know others who share the characteristics that make them eligible for inclusion in the study. Snowball sampling is quite suitable to use when members of a population are hidden and difficult to locate (e.g. samples of the homeless or users of illegal drugs) and these members are closely connected (e.g. organized crime, sharing similar interests, involvement in the same groups that are relevant to the project at hand). 1. Social computing Snowball sampling can be perceived as an evaluation sampling in the social computing field. For example, in the interview phase, snowball sampling can be used to reach hard-to-reach populations. Participants or informants with whom contact has already been made can use their social networks to refer the researcher to other people who could potentially participate in or contribute to the study. 2. Conflict environment It has been observed that conducting research in conflict environment is challenging due to mistrust and suspicion. A conflict environment, where people or groups thinks their needs and goal are contradictory to the goals and or needs of other people or group. These conflicts among groups or people include the differences to claim the area of territory, resources, trade, civil and religious rights that cause considerable misunderstanding and heighten the disagreements that lead to an environment with lack of trust and suspicion. In conflict environment, the entire population is marginalized to some extent rather than a specific group of people and makes it very hard for investigators to reach the study subjects to conduct the research. For example, a threatening political environment under authoritarian regime creates obstacles for the investigators to conduct the research. Snowball sampling has demonstrated as a second best method in conducting research in conflict environments like, in the context of the Israel and Arab Conflict. Snowball sampling allows the investigators to approach the marginalized population at cognitive and emotional level and enroll them in study. Snowball sampling address the conditions of lack of trust that arises due to uncertainty about the future through trace-linking methodology.