ACT Preparation / Unit 20 ACT 1919 short lesson, about 20 seconds
Observational Study Versus Experiment
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The idea
An observational study records what happens without assigning treatments; an experiment assigns them. Observational studies can show association but cannot by themselves show cause.
In practice
Surveying cyclists about helmet use is observational; assigning two helmet designs at random is an experiment.
Where people slip
A strong association in observational data still leaves confounding variables possible.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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