Which type of study manipulates variables to observe outcomes?

• A. Descriptive Study
• B. Observational Study
• C. Experimental Study
• D. Longitudinal Study

Answer: (C)

Manipulating variables to observe outcomes is what defines an experimental study. In this type of research, the investigator introduces a deliberate change to an independent variable and then measures its effect on a dependent variable, often using random assignment and a control group to isolate the influence of the manipulation. This setup is designed to reveal cause-and-effect relationships rather than merely describe or observe associations.

Descriptive studies, by contrast, summarize characteristics of a group without changing any conditions. Observational studies watch what happens in real life without interference from the researcher. Longitudinal studies follow the same participants over time to track changes, which can be descriptive or correlational but do not inherently involve purposeful manipulation of variables.