Question

which type of study assigns treatments to subjects to see what effect the treatments have on a response?
experiment
observational study
survey
comparative study

Explanation:

An experiment is a study where researchers assign treatments to subjects and observe the effect on a response. In an observational study, researchers only observe without assigning treatments. A survey is a method of collecting data through questions. A comparative study compares different groups or conditions but doesn't necessarily involve assigning treatments like an experiment does.

Answer:

Experiment