Answer: In an observational study, researchers do not control treatment, and in an experiment they do .
Explanation:
Observational study is the study where the researcher observes the subjects and measures variables, but does not influence the population where as in an experiment the experimenter has control on the independent variable to see the effect on the dependent variable.
So the correct difference between an observational study and an experiment is that "in an observational study, researchers do not control treatment, and in an experiment they do."