Opportunity (Convenience) Sampling: This involves selecting participants who are most easily available at the time of the study, such as people passing by in a public space.
Snowball Sampling: Used for hard-to-reach groups, where the researcher finds one participant who then refers them to others, creating a chain of contacts.
Quota Sampling: Similar to stratified sampling, researchers seek a specific number of people from various categories, but the selection within those categories is not random.
| Feature | Random Sampling | Non-Random Sampling |
|---|---|---|
| Selection Basis | Mathematical chance | Availability or researcher choice |
| Bias Risk | Low (objective) | High (subjective) |
| Generalizability | High (aims for representativeness) | Low (specific to the group) |
| Theoretical Link | Positivism (Quantitative) | Interpretivism (Qualitative) |
Identify the Frame: Always check if a 'sampling frame' (a list) is mentioned; if no list exists, the researcher must use non-random methods like snowball or opportunity sampling.
Proportionality Check: In stratified sampling questions, ensure the sample percentages match the population percentages to maintain representativeness.
Theoretical Alignment: Remember that Positivists favor random sampling for its scientific rigor, while Interpretivists value non-random sampling for gaining deep insight into specific social groups.
Common Error: Do not confuse 'Stratified' (random selection from groups) with 'Quota' (non-random selection from groups).
