The Difference Between an Experiment and an Observational Study Is

Multiple Choice

The difference between an experiment and an observational study is that

A) observational studies don't have explanatory and response variables.
B) experiments don't have placebos.
C) an experiment imposes treatments on subjects, while an observational study accepts existing treatments.
D) experiments are double-blind, while observational studies are only single-blind.
E) All of the above