The American Cancer Society is beginning a study to learn why some people never get cancer. To take part in the study, a person must be 30–65 years of age and never had cancer. The study requires that the participants fill out surveys about their health and habits and give blood samples and waist measurements. These surveys must be filled out every two years. The study is expected to last for the next 20 years?

Determine whether the study depicts an observational study or an experiment.