<prompt> Of the different epidemiological study designs available to test the association between risk factor and disease, the best design is of-Case-control studyEcological studyCoho studyCross-sectional study  <response>: - Coho study gives the strongest evidence of association. - Strength of association in coho study is calculated by: Relative risk - Best indicator as it has lower biases as compared to other studies. Attributable risk. Population attributable risk. 