4. A cohort study W to examine the association between high lipid level and coronary heart disease. Participants were classied as having either a high lipid level (exposed) or a low or normal lipid level (unexposed). Because age is associated with both lipid level and risk of heart disease, age was considered a potential confounder, and the age of each subject was recorded. The following data describes the study participantsw Developed CED No CHIN EXPOSED (High lipid level); young El} 393!\" old 200 5301} +4 UNEXPUSED (Low or normal lipid level) young 13 6932 old 65 29359 a. Calculate AND interpret the appropriate crude ratio measure of association combining the data for young and old individuals. (6 points)+J +1 h. For the same cohort study, perform a stratied analysis and calculate the appropriate stratumspecic ratio measures of association. 1What are they? (6 points)\" c. Do the data provide evidence of effect measure modication? Justify your answer. (6 points)4J