The difference between an observational study and an experiment is that
O in an observational study, only one group is studied, and in an experiment, two groups are studied.
O in an observational study, the researchers do not control treatment, and in an experiment, they do.
Oin an experiment, cause-and-effect is analyzed, and in an observational study, it is not.
in an experiment, one group is studied over a short period of time, and in an observational study, the group is
studied over a longer
period of time.