Which scenario is NOT a correlational study?

• A. A researcher measures hours of sleep and test scores without manipulating sleep
• B. A researcher manipulates lighting to observe mood changes
• C. A study examines relationship between exercise and heart rate in natural setting without intervention
• D. A study assesses the relationship between caffeine intake and productivity

Answer: (B)

In correlational designs, you look at two variables as they occur naturally and see if they vary together without manipulating anything. When a researcher deliberately changes a condition to see its effect on another variable, that’s an experiment, not a correlational study. Manipulating lighting to observe mood changes involves altering an independent variable and testing potential causal effects, which moves it out of correlational territory. The other scenarios describe simply observing relationships between variables—sleep and test scores, exercise and heart rate in a natural setting, caffeine intake and productivity—without any active manipulation. Therefore, the scenario with the manipulated lighting is not a correlational study.