1. Suppose a new study is planned, with 200 patients randomly assigned to each of a 400 IU per day vitamin E group and a 3 IU per day vitamin E group, and we record the exact survival time so that we do not have tied events. Assume that the survival rates in both groups are assumed the same as in Table 1, respectively. Also we assume that the relative hazard for the 400 IU/day group vs. the 3 IU/day group = 1.5. Then, how much power would a new study have if the maximum duration of follow-up is 4 years?
2. Suppose the same assumptions in (c). In addition, we assume that the censoring experience of both groups are assumed the same as for the 3 IU per day group in Table 1. How many subjects needto be enrolled in each group (assume equal sample size in each group) to achieve 80% power if a two-sided test is used with = .05?