23.3 Non-Probability Sampling

These methods do not give all elements a known probability of selection. They are used in exploratory research but are not suitable for making formal statistical inferences.

23.3.1 Convenience Sampling

Selecting individuals who are easiest to reach (e.g., mall surveys).

Pros: Quick and inexpensive
Cons: High risk of bias, not generalizable

23.3.2 Quota Sampling

Similar to stratified sampling but non-random.

Pros: Ensures subgroup representation
Cons: Subject to selection bias

23.3.3 Snowball Sampling

Used for hard-to-reach populations (e.g., networking through referrals).

Pros: Useful when the population is unknown
Cons: High bias, dependency on initial subjects