analyze whether more smokers than nonsmokers got lung cancer. Is this an experiment or an observational study?

analyze whether more smokers than nonsmokers got lung cancer. Is this an experiment or an observational study?

You would like to investigate whether smokers are more likely than nonsmokers to get lung cancer. You take the students in your class, select half at random and tell them to smoke a pack of cigarettes each day, and you tell the other half not to ever smoke. Fifty years from now, you will analyze whether more smokers than nonsmokers got lung cancer. Is this an experiment or an observational study?