Question

researchers call random radio listeners on the phone to rank five different popular songs. this research helps radio stations decide which songs to play more often. this method of gathering data is classified as
a census.
a sample survey.
an experiment.
an observational study.

Explanation:

1. A census involves collecting data from every member of a population. Here, researchers are only calling random radio listeners (not all), so it's not a census.
2. A sample survey is when data is collected from a subset (sample) of the population to make inferences about the whole. The researchers are calling random listeners (a sample) to gather data about song preferences, which fits a sample survey.
3. An experiment involves manipulating variables and observing the effect, but here there's no manipulation, just data collection from listeners.
4. An observational study involves observing without interfering, but this is a survey (asking for rankings) rather than just observing.

Answer:

B. a sample survey.