In a college where 25% of students live in campus housing and 75% off campus, a researcher randomly selects 25 housing students and 75 off-campus students to form 100. What technique is this?

• A. Systematic sampling
• B. Stratified sampling
• C. Cluster sampling
• D. Simple random sampling

Answer: (B)

The technique shown is stratified sampling. The population is divided into meaningful subgroups (housing vs. off-campus students), and then samples are drawn from each subgroup in a way that matches their share in the population. Choosing 25 housing students and 75 off-campus students mirrors the 25%–75% distribution of the whole college, which is proportional allocation within stratified sampling. This approach helps ensure that both subgroups are represented in the final sample, reducing bias that could occur if you sampled from the entire population without regard to subgroup membership. It’s not systematic sampling, which uses a fixed interval; not cluster sampling, which would select whole groups or locations; and not simple random sampling, which would treat all students equally without guaranteeing subgroup representation.