What is the difference between random sampling and random assignment?

• A. Random sampling assigns participants to groups; random assignment selects sample.
• B. Random sampling selects participants from population; random assignment places those participants into conditions randomly.
• C. Random sampling is about groups; random assignment is about measurements.
• D. Random sampling and random assignment are identical.

Answer: (B)

The main idea is to understand two different processes in study design: how you choose participants from a population, and how you allocate those participants to different groups or conditions.

Random sampling is about who is included in the study. You use a random process to select participants from the larger population so your sample reflects that population, which helps you generalize findings beyond the study.

Random assignment is about where those selected participants end up in the study. After you have your sample, you randomly place participants into different experimental conditions (like treatment vs. control) to ensure any differences between groups are due to the manipulation rather than preexisting differences.

The best description is that random sampling selects participants from the population, and random assignment places those participants into conditions randomly. The other options mix up these roles or misstate their purpose, and they don’t capture the distinct goals of sampling versus assignment.