Answer
This observational study on cancer is a cohort study. Cohort studies are carried on for a very long period of time, and at the end of it the changes in the response variable are observed. The participants filled out a questionnaire in 1982 and they are under observation since then.
Work Step by Step
Cohort studies are prospective and forward looking, where participants are observed over long periods of time. Case-control studies are retrospective, and cross-sectional studies are carried out for a very short interval. Hence, this study can only be a cohort study.
