Statistical analysis With an estimated distribution of 60% / 40% between aspirin alone and aspirin + clopidogrel groups and assuming an alpha risk of 0.05 and a beta risk of 0.20 and a mean amount of postoperative bleeding after CABG in the aspirin-alone group of 400 +/- 200 mL, we calculate that at least 136 patients at all (85 in aspirin alone and 51 in aspirin + clopidogrel) are required to demonstrate that the amount of bleeding in the aspirin+clopidogrel was not more than 25% increased compared to the bleeding in aspirin alone group (non inferiority study).