<prompt> Interventional study is used for:-Hypothesis FormulationHypothesis TestingHypothesis ConfirmationHypothesis Manipulation  <response>: CLASSIFICATION OF EPIDEMIOLOGICAL STUDIES: 1. OBSERVATIONAL STUDIES: - Descriptive studies - Hypothesis formation is done - Analytical studies - Hypothesis testing is done by coho study case-control cross-sectional Ecological studies. 2. EXPERIMENTAL INTERVENTIONAL STUDIES: - Hypothesis confirmation is done - Done by clinical trials RCTs Field trials Community trials. 