Introduction to non-random sampling

Non-random sampling is used because certain groups - like housewives, doctors, or skateboarders - may not be evenly distributed in the general population, making random methods inefficient. As a result, sociologists choose non-random methods to build samples that directly address their research questions, though these can introduce biases if not managed carefully.

Key types of non-random sampling:

• Snowball sampling
• Purposive sampling
• Opportunity sampling
• Quota sampling
• Volunteer sampling

Snowball sampling

Snowball sampling is a technique where researchers start with a small number of participants and expand the sample through personal introductions and referrals. This method is effective for studying hidden or hard-to-access groups, such as deviant or criminal groups. A sociologist might begin with one contact who then introduces others, creating a "snowball" effect that grows the sample over time.

Method

The researcher identifies an initial participant, often from a deviant or criminal group, who provides referrals to similar individuals. For example, a study on drug users might start with one addict who introduces the researcher to others in their circle.

Limitations

Participants who agree to cooperate may not be typical of the group, as those willing to share information could differ from more secretive members. This can lead to bias, especially in highly private communities.

Purposive sampling

Researchers target individuals or groups that fit precise criteria, as it would make no sense to use other social groups. In his research on affluent workers, sociologist John Goldthorpe purposively selected workers from a car factory because he knew they earned high wages, making them ideal for exploring class and income dynamics.

Opportunity sampling

Researchers capitalise on timely events to recruit. For example, sociologists studying fan culture might attend a Star Trek convention to survey attendees, or interview voters exiting polling stations on election day. The sample may not be representative.

Quota sampling

Often used in public spaces like streets or shopping centres, researchers approach individuals matching specific traits until quotas are met. For example, market researchers might seek a set number of housewives or older people. This method is prone to researcher bias, as individuals may unconsciously select cooperative people while overlooking marginalised groups like the homeless or youth. This reduces the sample's objectivity and generalisability.

Volunteer sampling

Participants are recruited via advertisements, such as posters in a student union or newspaper ads. This is useful for sensitive topics where other methods fail, like studies on sexual behaviour among students. Volunteers may not be typical, leading to an unrepresentative sample.

Access and gatekeeping in sampling

Accessing exclusive or deviant groups - those that isolate themselves from mainstream society - presents significant challenges in sociological research. These groups, such as criminal networks, often require careful strategies to ensure ethical and safe entry.

Gatekeeping

Gatekeeping refers to the role of an intermediary who facilitates access by vouching for the researcher. This person, trusted by the group, acts as a "gatekeeper" to build credibility and reduce suspicion.

Strategies for gaining access:

• Using gatekeepers - A respected figure within the group can introduce the researcher and encourage cooperation. For example, sociologist Sudhir Venkatesh gained entry to a Chicago crack cocaine gang, the Black Kings, through the gang leader who instructed members to participate.
• Offering services - Researchers might provide value, such as legal advice, to earn trust and access.