Between-groups manipulation vs within-groups manipulation, which statement is true?

Between-groups manipulation vs within-groups manipulation, which statement is true?

• A. Between-groups involves different participants receiving different levels of the IV, while within-groups has each participant receiving all levels of the IV.
• B. Between-groups involves the same participants receiving all levels of the IV.
• C. Within-groups uses different participants for each level.
• D. Both designs use identical participants across levels.

Answer: (A)

The key idea is how participants are assigned to the levels of the independent variable. In a between-groups design, different participants are assigned to each level, so each person experiences only one level of the IV. In a within-subjects (or within-groups) design, the same participants experience all levels of the IV, allowing for direct within-person comparisons. The statement that captures this correctly says that between-groups uses different participants for each level, while within-groups has each participant receiving all levels of the IV. That aligns with the usual definitions. Thinking about the other options helps see why this is the best choice: saying the same participants receive all levels describes within-subjects, not between-groups; saying within-groups uses different participants for each level is the opposite of what happens; and saying both designs use identical participants across levels is true only for within-subjects, not for between-groups.

The key idea is how participants are assigned to the levels of the independent variable. In a between-groups design, different participants are assigned to each level, so each person experiences only one level of the IV. In a within-subjects (or within-groups) design, the same participants experience all levels of the IV, allowing for direct within-person comparisons.

The statement that captures this correctly says that between-groups uses different participants for each level, while within-groups has each participant receiving all levels of the IV. That aligns with the usual definitions.

Thinking about the other options helps see why this is the best choice: saying the same participants receive all levels describes within-subjects, not between-groups; saying within-groups uses different participants for each level is the opposite of what happens; and saying both designs use identical participants across levels is true only for within-subjects, not for between-groups.