Practice and fatigue effects are both problems with A. cross-sectional designs B. independent measures C. within-participant designs D. between-group designs

The correct answer is C. within-participant designs.

Here's why:

A. Cross-sectional designs: These are not typically affected by practice or fatigue effects because different groups of participants are used at each level of the independent variable.

B. Independent measures: This design also avoids practice and fatigue effects because each participant is only tested once.

C. Within-participant designs: In this design, the same participants are used in all the conditions of an experiment. Therefore, they are susceptible to practice effects (improvement in performance with repeated testing) and fatigue effects (deterioration in performance with repeated testing).

D. Between-group designs