Final answer:
Between-subjects experiments involve different groups of participants and within-subjects experiments involve the same group of participants. The choice depends on the research question and the nature of the variables.
Step-by-step explanation:
Between-subjects experiments involve different groups of participants being exposed to different conditions or treatments. Each group represents a different level of the independent variable. For example, in a study on the effects of caffeine on alertness, one group may receive a caffeinated beverage, while another group receives a non-caffeinated beverage.
Within-subjects experiments involve the same group of participants being exposed to different conditions or treatments. Each participant serves as their own control. For example, in a study on the effects of caffeine on alertness, participants may receive both a caffeinated beverage and a non-caffeinated beverage on different days.
The choice between between-subjects and within-subjects experiments depends on the research question, the nature of the variables, and practical considerations. Between-subjects experiments are useful when there may be individual differences between participants and when the independent variable may have lasting effects. Within-subjects experiments are useful when it is important to control for individual differences and when the independent variable is expected to have temporary effects.