Which of the following is a type of sampling technique used to ensure representation across subgroups?

• A. Cluster
• B. Random
• C. Stratified
• D. Systematic

Answer: (C)

Stratified sampling ensures representation across subgroups by dividing the population into homogeneous subgroups (strata) that share a characteristic relevant to the study, and then sampling from each stratum. This guarantees that each subgroup is represented in the final sample, which improves precision for overall estimates and for subgroup-specific insights. For example, if evaluating property values across neighborhoods with different price levels, you’d create strata for each neighborhood or price tier and sample from each one, either proportionally to its size or by a fixed number of observations per stratum. The other methods don’t inherently ensure that all subgroups are represented: random sampling may miss small subgroups, cluster sampling focuses on whole clusters and can underrepresent some groups, and systematic sampling uses a fixed interval that might align with patterns in the list and fail to capture certain subgroups.