In a within-subjects experimental design, which statement is true?

• A. Different groups measured
• B. The same subjects measured under multiple conditions
• C. Random assignment
• D. Control group for baseline

Answer: (B)

Within-subjects designs have the same participants tested under every level of the independent variable. This means each person experiences all conditions, so every comparison is made within the same individuals. That setup controls for individual differences, reducing random variability and often giving you more statistical power with fewer participants. It also introduces potential carryover or practice effects, which researchers mitigate with counterbalancing the order of conditions.

Measuring different groups would describe a between-subjects design, where separate groups participate in different conditions. Random assignment is a common experimental method but does not define the design type by itself. Having a control group for a baseline can occur in many designs and isn’t the defining feature of a within-subjects approach.