Type of Copula      τ Global Power                            PFS                             OS
      1st Interim Final Analysis Power 1st Interim Final Analysis Power
Independence 0 0.979 0.206 0.647 0.853 0.221 0.855 0.856
Normal 0.10 0.969 0.205 0.645 0.851 0.211 0.849 0.849
  0.30 0.955 0.202 0.646 0.848 0.217 0.852 0.853
  0.50 0.934 0.209 0.639 0.849 0.216 0.860 0.860
  0.70 0.912 0.203 0.644 0.847 0.209 0.855 0.856
Frank 0.10 0.974 0.203 0.646 0.850 0.206 0.856 0.857
  0.30 0.957 0.207 0.645 0.852 0.215 0.856 0.857
  0.50 0.938 0.203 0.647 0.850 0.218 0.852 0.853
  0.70 0.912 0.204 0.640 0.844 0.215 0.854 0.855
Gumbel 0.10 0.969 0.209 0.638 0.846 0.221 0.853 0.854
  0.30 0.947 0.208 0.638 0.846 0.217 0.854 0.854
  0.50 0.929 0.208 0.639 0.847 0.210 0.857 0.857
  0.70 0.909 0.212 0.638 0.850 0.216 0.854 0.855
Table 2: Empirical global power, power for each endpoint and proportion of terminating the trial early assuming equal allocation of type I error rate of 0.025 for each endpoint and using O'Brien-Fleming boundaries; results based on 10,000 simulations.