Compare simple random sampling and stratified sampling in terms of representativeness and when stratification is useful.

Compare simple random sampling and stratified sampling in terms of representativeness and when stratification is useful.

• A. Simple random sampling guarantees representativeness across all subgroups; stratified sampling is only for large populations.
• B. Simple random sampling stratifies by subgroup after collection.
• C. Stratified sampling reduces representativeness but increases variance.
• D. Simple random gives each unit equal chance; stratified ensures representation of subgroups to improve precision and subgroup analyses.

Answer: (D)