In which design are the same participants used in all the conditions?

• A. Repeated measures (within subjects) design
• B. Independent samples design
• C. Cross-sectional design
• D. Observational design

Answer: (A)

This item tests the idea of a repeated measures (within-subjects) design, where the same participants experience every condition. Because each person acts as their own control, individual differences don’t add noise across conditions, giving you greater statistical power and often a smaller needed sample size. But this setup can bring order effects—what happens in one condition can influence performance in later ones due to practice, fatigue, or carryover. To reduce these issues, researchers counterbalance the order of conditions, randomize it, or use designs like Latin squares.

By contrast, an independent samples design uses different participants for each condition, so there’s no carryover but you need more participants and must account for between-subject variability. A cross-sectional design looks at different groups at a single point in time without manipulating conditions. An observational design involves watching behavior as it occurs naturally, without assigning people to different conditions.