For each of the following statements, indicated whether the statistical association is likely a result of chance, bias or confounding and provide a brief explanation. (2 points each) 1. A case-control study found a positive association between self-reported secondhand smoke exposure during childhood and cardiovascular disease as an adult. Answer: Explanation: 2. A cohort study found no statistical association between smoking and pulmonary fibrosis. Answer: Explanation: 3. A hospital-based case-control study identified a strong association between estrogen therapy and heart attacks. Many doctors suspected the association and hospitalized some women who were on estrogen therapy for evaluation. Answer: Explanation: 4. A small prospective cohort study found that those who were exposed to per- and polyfluoroalkyl substances, also known as PFAS, from an environmental exposure did not have a significantly greater risk of developing cancer compared to those who were not exposed. The risk ratio was >1 but the confidence interval was very wide and included 1. (RR= 1.35; 95% confidence interval 0.14-55.01). Answer: Explanation: 5. A case-control study showed a strong association exists between physical inactivity and heart disease. Answer: Explanation: