Stratification and Effect Measure Modification (Chapter 13) A cohort study was undertaken to examine the association between high lipid level and coronary heart disease. Participants were classified as? 1) Group a ________. High lipid level and coronary heart disease 2) Group B: High lipid level and no coronary heart disease 3) Group C: Normal lipid level and coronary heart disease 4) Group D: Normal lipid level and no coronary heart disease