Sampling and Observational Studies

1. The population is all of the vehicles that pass through the lane with the camera; the sample is the group of every tenth vehicle that passes through the lane.

2. The population is all adult patrons of the library; the sample is the $150$ patrons selected.

3. The population is the parents of the pediatrician's patients; the sample is the $10$ parents of patients selected.

4. The population is everyone listed in the city phone directory; the sample is the $75$ people selected.