Observational study
SAT glossary · Math
Definition
Researchers measure without intervening and subjects self-select into groups; the design licenses association only, always. An option asserting causation from one is wrong regardless of how plausible the causal story is.
Observational study in plain English
An observational study is one where researchers just WATCH and measure what's happening, without actively controlling who gets what — the people being studied basically choose their own groups (self-select) rather than being randomly assigned. Because nothing was controlled, this kind of study can only ever show you an ASSOCIATION between two things — it can never prove that one thing CAUSES the other, no matter how convincing or obvious the story sounds. So any answer choice claiming a cause-and-effect relationship from an observational study is automatically wrong, purely because of the study's design — not because the claim itself seems unreasonable.
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