Question

researchers periodically survey a few thousand of the patients taking a certain medication in order to make connections between that medication and the subjects’ general health. this method of gathering data is classified as
○ a census.
○ a sample survey.
○ an experiment.
○ an observational study.

Explanation:

• A census surveys an entire population, but here only a few thousand patients (a sample) of all taking the medication are surveyed, so not a census.
• A sample survey involves collecting data from a subset (sample) of a population to make inferences. Here, researchers survey a few thousand (a sample) of all patients taking the medication, which fits a sample survey.
• An experiment involves manipulating variables, but here there's no manipulation—just surveying to find connections, so not an experiment.
• An observational study observes without intervention, but the key here is using a sample (few thousand) from the population of patients on the medication, which is a sample survey (focused on sampling) rather than just observing (observational study can be on a whole population or sample, but the sampling aspect is central here).

Answer:

B. a sample survey