Which statement best captures the difference between experimental and non-experimental designs?

• A. Experimental designs manipulate an independent variable and use random assignment to establish causality.
• B. Non-experimental designs manipulate variables and use random assignment to establish causality.
• C. Experimental designs rely on observational data without manipulation.
• D. Non-experimental designs use random assignment but cannot assess relationships.

Answer: (A)

The key idea here is how experimental designs differ from non-experimental ones in establishing causality. In an experimental design, the researcher actively changes the independent variable and uses random assignment to place participants into groups. This combination helps control for other factors that could influence the outcome, so observed differences in the dependent variable are more convincingly due to the manipulation, supporting causal inferences.

Non-experimental designs, on the other hand, observe variables as they occur without manipulating them. They may compare existing groups or examine relationships, but the lack of random assignment and controlled manipulation makes it harder to rule out alternative explanations, so causal claims are weaker.

So the statement that best captures the difference is that experimental designs manipulate an independent variable and use random assignment to establish causality.