What is the difference between between-subjects and within-subjects designs?

The distinction between between-subjects and within-subjects designs is fundamental in experimental research strategy. The correct answer emphasizes that between-subjects designs involve different participants assigned to each group or condition being tested. This means that each participant experiences only one condition, thus reducing the potential for carryover effects that can occur if the same participants were to partake in multiple conditions, which is the approach taken in within-subjects designs.

By using different participants for each group, researchers can isolate the effects of the independent variable without contamination from previous conditions experienced by the same subjects. This design is particularly useful when the effects of a treatment might affect participants in ways that could cloud the results of subsequent treatments.

While other options mention aspects of these designs, the focus on participant usage clarifies the key operational difference, illustrating how each design affects the interpretation of data and the conclusions that can be drawn from an experiment.