10.2 Sample Size Considerations Assuming a 3-year event rate of 4.2% based on recently published literature10;11;26;27 and alpha error rate of 5%, 2500 patients provides over 90% power to detect a hazard ratio of 1.5 for at least one risk factor in the Cox model. An additional 250 (2750 total) patients will be enrolled to compensate for a projected dropout rate of 2% per year.