Which research design involves systematic manipulation and comparison of groups?

• A. Observational
• B. Experimental
• C. Descriptive
• D. Qualitative

Answer: (B)

Experimental design involves systematically manipulating an independent variable and comparing outcomes across groups. Researchers assign participants to different conditions, including a control group, and measure the impact on a dependent variable. Random assignment helps ensure the groups are comparable, so observed differences can be attributed to the manipulation rather than other factors. This approach is especially powerful for testing causal relationships because it controls for confounding variables through design rather than merely observing natural variation.

Observational studies, by contrast, watch what happens without assigning or altering conditions. Descriptive studies summarize characteristics of a sample or phenomenon, without testing hypotheses about causes. Qualitative studies focus on exploring meanings, experiences, and processes, often using non-numeric data, and do not primarily aim to compare controlled groups to infer causality.