Answer
Cross-sectional study, case-control study, and cohort study are the types of observational study.
Work Step by Step
In a cross-sectional study, the data is collected at a particular point in time or over a short period of time. A case-control study is retrospective, which means individuals have to look back in time to collect the data. Cohort study first collects the data and then it is observed over a long period of time.
