Snowball sampling, also known as chain referral sampling or network sampling, is a non-probability sampling technique used in qualitative research It involves recruiting study participants through referrals from initially sampled participants. Snowball sampling is useful for reaching populations that are difficult for researchers to access otherwise
How Does Snowball Sampling Work?
Snowball sampling starts with identifying people who meet the eligibility criteria and can participate in the study These first participants are called “seeds” You then ask the seeds to recommend other people they know who also qualify for your study, Those people are recruited and then asked to provide further recommendations, This cycle continues until the target sample size is reached,
The sample builds through waves of recruitment like a snowball growing in size as it rolls down a hill. That’s how this method gets its name.
Three Types of Snowball Sampling
There are a few variations on snowball sampling to suit different research needs:
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Linear snowball sampling: Each participant recruits one additional participant. This is best for studies with minimal eligibility criteria.
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Exponential non-discriminative snowball sampling: Each participant provides multiple referrals, all of whom are recruited. This allows you to reach a larger sample quickly.
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Exponential discriminative snowball sampling: Each participant provides multiple referrals, but the researcher screens and selects only some to recruit based on the study criteria. This allows for more control over the sampling.
When Is Snowball Sampling Used in Research?
Snowball sampling is commonly used in the following research scenarios:
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Studying rare or stigmatized populations: People may be hesitant to participate in research on sensitive topics. Snowball sampling leverages referrals among trusted social networks to access hidden or hard-to-reach groups.
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Exploring social networks and relationships: Snowball sampling is useful for studying how people are interconnected and the characteristics of their relationships.
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Recruiting dispersed or isolated populations: Referral-based recruitment can help access people who are geographically spread out.
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Pilot studies: Snowball sampling offers a quick, low-cost way to recruit an initial sample to pre-test research protocols and measures.
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Qualitative research: Snowball samples are prone to bias, so this method is better suited to qualitative research focused on analyzing themes rather than generalizing statistically.
The Advantages and Disadvantages of Snowball Sampling
Snowball sampling provides some benefits as well as limitations to consider:
Advantages
- Provides access to hidden or hard-to-reach populations
- Saves time and money in recruitment
- Allows study of social networks and relationships
- Flexible, referral-driven recruitment approach
Disadvantages
- Prone to sampling bias
- Little control over sample composition
- Sample likely not representative of population
- Difficult to calculate sampling error
- Referral process could break down
How to Conduct Snowball Sampling
If you determine snowball sampling aligns with your research goals, here are some tips for implementation:
- Carefully define the eligibility criteria for your sample
- Identify multiple seeds to initiate referrals
- Interact personally with participants to explain the study and gain trust
- Maintain confidentiality of participants at all stages
- Continue recruitment until reaching the target sample size
- Use snowball sampling alongside other methods to minimize limitations
Examples of Snowball Sampling in Research
Snowball sampling has been used successfully across diverse research areas, including:
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A study exploring the experiences of undocumented immigrants in the U.S. used snowball sampling to recruit this hidden population.
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Researchers investigating social networks of heroin users in the Netherlands utilized snowball sampling to map connections.
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A pilot study on improving screening for domestic violence recruited an initial sample of patients through snowball sampling.
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An exploratory study on stress among graduate students seeded recruitment with personal and professional contacts.
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Public health researchers studied tobacco use within LGBTIQ communities using snowball sampling.
Snowball sampling leverages social networks to recruit hard-to-reach or hidden populations in a flexible, organic way. It works well for qualitative research focused on social relationships and exploratory studies with stigmatized groups. However, snowball samples are prone to bias and unlikely to represent the broader population. Careful planning is needed to maximize the benefits of this sampling technique while minimizing the limitations.
Types of Snowball Sampling
- Linear Snowball Sampling: The formation of a sample group starts with one individual subject providing information about just one other subject and then the chain continues with only one referral from one subject. This pattern is continued until enough number of subjects are available for the sample.
- Exponential Non-Discriminative Snowball Sampling: In this type, the first subject is recruited and then he/she provides multiple referrals. Each new referral then provides with more data for referral and so on, until there is enough number of subjects for the sample.
- Exponential Discriminative Snowball Sampling: In this technique, each subject gives multiple referrals, however, only one subject is recruited from each referral. The choice of a new subject depends on the nature of the research study.
Learn more: How to Determine Sample Size for your Next Survey
Advantages of Snowball Sampling
- It’s quicker to find samples: Referrals make it easy and quick to find subjects as they come from reliable sources. An additional task is saved for a researcher, this time can be used in conducting the study.
- Cost effective: This method is cost effective as the referrals are obtained from a primary data source. It’s is convenient and not so expensive as compared to other methods.
- Sample hesitant subjects: Some people do not want to come forward and participate in research studies, because they don’t want their identity to be exposed. Snowball sampling helps for this situation as they ask for a reference from people known to each other. There are some sections of the target population which are hard to contact. For example, if a researcher intends to understand the difficulties faced by HIV patients, other sampling methods will not be able to provide these sensitive samples. In snowball sampling, researchers can closely examine and filter members of a population infected by HIV and conduct a research by talking to them, making them understand the research objective, and eventually, analyzing the received feedback.
Snowball Sampling – Cin, Joanne & Aiko
What is an example of snowball sampling?
The most obvious example of this would be a simple random sample. There are some advantages to using snowball sampling, including: Researchers can reach subjects in a particular population that would otherwise be difficult or impossible to reach. Snowball sampling is low-cost and easy to implement.
What is exponential discriminative snowball sampling?
Exponential discriminative snowball sampling is most used when screening participants according to specific criteria is vital to your research goals. In researching the motivations of tiny house owners, you decide you only want to focus on those who bought one in the past three years.
What is snowball sampling in sociology?
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.
When is snowball sampling used in qualitative research?
Snowball sampling is often used in qualitative research when the population is hard-to-reach or hidden. It’s particularly useful when studying sensitive topics or when the members of a population are difficult to locate. The process starts with a small group of initial respondents (seeds).
