Question

define representative sample

Answer 1

A representative sample is a subset of a population whose characteristics (on the variables that matter for the study) closely match those of the entire population, so findings from the sample can be generalized to the population with minimal bias.

Key points
- It reflects the same distribution of important characteristics (e.g., age, sex, income, ethnicity, behavior) as the population.
- Representativeness is about composition, not just size: a large sample can be unrepresentative; a smaller, well-chosen sample can be representative.
- A representative sample reduces sampling bias and increases the validity of inferences about the whole population.

Common ways to obtain a representative sample
- Simple random sampling
- Stratified sampling (ensures proportional representation of key subgroups)
- Cluster sampling (when populations are naturally grouped)
- Systematic sampling (when a properly randomized list exists)
- Post-survey weighting (to adjust for known differences between sample and population)

Pitfalls
- Convenience sampling, volunteer/self-selection, and poor sampling frames often produce unrepresentative samples.
- Nonresponse bias can make an otherwise good design unrepresentative.
- Misidentifying which characteristics are important can lead to misleading “representativeness.”

Example
If a city is 60% renters and 40% homeowners, a representative sample for a housing study would have roughly the same 60/40 split (or be weighted to reflect it) so conclusions apply to the whole city.