In a study to support drug discovery for patients with lung cancer, patients were divided into3

groups based on the severity of the disease. Smoking and alcohol consumption habits were recorded for all3

groups. Is this an example of an observational study or experimental study?

If it is experiment. The controlled factor is the smoking and alcohol consumption habits.

Also if it is experiment is the controlled factor the severity of the disease.

Is the study is an observational study.

And if it is experiment is the controlled factor iswhether or not the person has lung cancer