Back to Distinguish surveys, experiments, and observational studies — Problem 5 · Task Set 14

Exercises: Distinguish Surveys, Experiments, and Observational Studies

Work through each section in order. For classification problems, decide whether a study is a sample survey, an observational study, or a randomized experiment, and use two separate questions: "Was there random SELECTION?" (which governs whether results generalize to a population) and "Was there random ASSIGNMENT?" (which governs whether a difference can be read as causation). For explanation problems, write in complete sentences.

Grade 10·21 problems·~35 min·Common Core Math - HS Statistics and Probability·group·hss-ic-b-3

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Fluency Practice

Classify each study and identify the role of randomization.

A drug is tested on 200 volunteers (not a random sample of any population). The volunteers are randomly assigned to the drug or a placebo, and the drug group recovers faster. To whom can this causal result be generalized?

Only as far as the volunteers represent a broader group; random assignment earns causation within these subjects, but without random selection the result does not automatically generalize to everyone.

To the entire population, because the study was randomized.

To no one, because experiments never generalize.

To everyone who is similar in age only, regardless of how subjects were obtained.