Question

there are many types of studies that can be conducted to make observations about biological phenomena. observational studies and controlled experimental studies are two such types. sort each of the following descriptions according to whether it describes an observational study or a controlled experimental study.
makes observations without directly manipulating test subjects
can determine causation
can only determine correlation, not causation
deliberately changes one variable while holding others constant
observational study
controlled experimental study
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Explanation:

• Observational study: In an observational study, researchers observe and collect data without interfering or manipulating variables. So "makes observations without directly manipulating test subjects" and "can only determine correlation, not causation" fit here because there's no manipulation to establish cause - effect, only to see relationships.
• Controlled experimental study: In a controlled experiment, researchers manipulate one variable (the independent variable) while keeping others constant (control variables) to see the effect on another variable (dependent variable). This manipulation allows them to determine causation. So "can determine causation" and "deliberately changes one variable while holding others constant" fit here.

Answer:

• Observational study: makes observations without directly manipulating test subjects; can only determine correlation, not causation
• Controlled experimental study: can determine causation; deliberately changes one variable while holding others constant