the difference between an observational study and an experiment is thatin an observational study only one group is studied, and in an experiment two groups are studied in an observational study, researchers do not control treatment, and in an experiment they doin 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

Answer: In an observational study, researchers do not control treatment, and in an experiment they do .Step-by-step 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."