Snowball sampling is a process of selecting a sample using
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Snowball sampling is a recruitment technique in which research participants are asked to assist researchers in identifying other potential subjects. The use of currently enrolled research participants to recruit additional research participants (sometimes referred to as “the snowball sampling”) may be approved by the IRB under some circumstances. However, the protocol must include justification of the use of this method in the context of the study and target population. The method that minimizes risk would be the preferred choice. For example, a researcher seeking to study patterns of informal leadership in a community may ask individuals to name others who are influential in a community.1 If the topic of the research is not sensitive or personal, it may be acceptable for subjects to provide researchers with names and contact information for people who might be interested in participation. If the topic is sensitive or personal, snowball sampling may be justified, but care should be taken to ensure that the potential subjects' privacy is not violated. For example, studies of networks of drug users or studies tracking sex partners require extreme caution with information gathered from one subject about another. The steps taken to minimize the risk of violating an individual’s privacy should be articulated in the recruitment section of the protocol. Current participants cannot receive incentives or compensation for referrals. Acceptable alternatives that reach the same potential subjects include: • The study team member may provide information to subjects and encourage them to pass it on to others who may be interested or eligible. The information provided to enrolled subjects (fliers, letters of explanation, etc.) must be approved by the IRB. Interested prospective participants could then contact the project for more info and possible inclusion. • The study team member may ask subjects to obtain permission from others prior to disclosing their contact information. In this scenario, the researcher would not directly contact the referred/potential subject without permission from the potential subject and would not have access to any information about a potential subject without permission from that individual. Snowball sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find. It’s called snowball sampling 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. Snowball sampling consists of two steps:
These steps are repeated until the needed sample size is found. Ethically, the study participants should not be asked to identify other potential participants. Rather, they should be asked to encourage others to come forward. When individuals are named, it’s sometimes called “cold-calling”, as you are calling out of the blue. Cold-calling is usually reserved for snowball sampling where there’s no risk of potential embarrassment or other ethical dilemmas. For example, it would be easier to cold-call participants in a study for families who regularly dine at fast-food restaurants than it would be to cold-call people who are having extra-marital affairs. Snowball sampling can be a tricky ethical path to navigate. Therefore, you’ll probably be in contact with an institutional review board (like this one) or another department similarly involved in ethics. Why is Snowball Sampling Used?Some people may not want to be found. For example, if a study was investigating cheating on exams, shoplifting, drug use, prostitution, or any other “unacceptable” societal behavior, potential participants would be wary of coming forward because of possible ramifications. However, other study participants would likely know other people in the same situation as themselves and could inform others about the benefits of the study and reassure them of confidentiality. Advantages and Disadvantages of Snowball SamplingAdvantages:
Disadvantages:
Snowball sampling is also known as cold-calling, chain sampling, chain-referral sampling, and referral sampling. ReferencesEveritt, B. S.; Skrondal, A. (2010), The Cambridge Dictionary of Statistics, Cambridge University Press. CITE THIS AS: Need help with a homework or test question? With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. Your first 30 minutes with a Chegg tutor is free! |
