When designing a psychological study, it is important to understand the differences and similarities between different types of research designs. Two useful comparisons are between between-subjects and within-subjects designs and small N and large N designs. Between-Subjects vs. Within-Subjects Designs: A between-subjects design involves using different groups of participants, with each group only experiencing one condition of the experiment. For example, one group might receive a treatment, while another group does not. In contrast, a within-subjects design uses the same participants in all conditions. This means every person gets to try each version of the treatment or task. Similarity: Both designs aim to test how a treatment or condition affects behavior and can show cause-and-effect relationships. Difference: Between-subjects designs avoid practice or fatigue effects but require more participants. Within-subjects designs use fewer participants and reduce individual differences by comparing each person to themselves (Cozby & Bates, 2024). A within-subjects design would be useful when you want to measure how something affects the same person over time, like testing memory before and after a study session. Small N vs. Large N Designs: A small N design focuses on just a few participants, often studying them in detail, such as in therapy or studies involving rare disorders. A large N design uses many participants to find general patterns in behavior