SAT Math: Distinguish observational studies from experiments
15+ practice questions in Praczo
The concept, explained
- 1
In an observational study, the researcher records data without intervening. In an experiment, the researcher actively assigns subjects to treatment and control groups.
- 2
Only well-designed experiments (with random assignment) can establish causation. Observational studies can only show association.
- 3
Random assignment to treatment is different from random sampling. Random sampling supports generalization; random assignment supports causal inference.
- 4
Look for the verb: if researchers "gave" or "assigned" a treatment, it's an experiment; if they "recorded" or "observed," it's observational.
- ✗ Confusing random sampling with random assignment. Both matter, but they support different conclusions.
- ✗ Assuming an observational study with a large sample can prove causation. It cannot.
SAT-style practice
A researcher divides 200 volunteers into two groups at random. One group takes a new vitamin daily; the other takes a placebo. After 8 weeks, the researcher compares reported energy levels. This study is best described as
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