A good experiment has a few moving parts, and each one has a job. The researcher changes one thing, the independent variable. The researcher measures another, the dependent variable. A control group and random assignment make sure the treatment is the only real difference between the groups. Tap any labeled part to see its job. Then run the study yourself and see what goes wrong when a part is missing.
A randomized experiment
Run the study
How are people put into groups?
What does the control group get?
Who knows who got caffeine?
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Does caffeine improve memory?tap a labeled part to see its job