An Experiment Is Usually Preferred to an Observational Study Because

Multiple Choice

An experiment is usually preferred to an observational study because

A) one can draw a cause and effect conclusion in an experiment but not in an observational study.
B) it is easier to collect data from an experiment than it is from an observational study.
C) it is cheaper to run an experiment than it is to do an observational study.
D) volunteers can be used for an experiment but not for an observational study.