Table 5.

Empirical global type I error rates, empirical significance level for each endpoint and proportion of not terminating the trial early using O’Brien-Fleming boundaries and assuming unequal allocation of the type I error rate of 0.03 for PFS and 0.02 for OS; results based on 10,000 simulations

Type of Copula	τ	Empirical Global Type I	PFS			OS
		Error Rate	1st Interim	Final Analysis	Type I Error	1st Interim	Final Analysis	Type I Error
Type-I error rate		0.05	0.00042	0.02990	0.03	0.0014	0.01938	0.020
Independence	0	0.048	0.0004	0.0305	0.0307	0.0009	0.0176	0.0178
Normal	0.10	0.051	0.0008	0.0310	0.0318	0.0011	0.0199	0.0202
	0.30	0.049	0.0005	0.0294	0.0295	0.0016	0.0211	0.0220
	0.50	0.046	0.0003	0.0312	0.0315	0.0006	0.0194	0.0195
	0.70	0.039	0.0002	0.0302	0.0304	0.0001	0.0188	0.0192
Frank	0.10	0.045	0.0004	0.0254	0.0258	0.0013	0.0192	0.0196
	0.30	0.049	0.0006	0.0300	0.0306	0.0015	0.0188	0.0194
	0.50	0.045	0.0002	0.0302	0.0304	0.0016	0.0184	0.0191
	0.70	0.041	0.0001	0.0301	0.0302	0.0013	0.0176	0.0183
Gumbel	0.10	0.050	0.0005	0.0296	0.0301	0.0016	0.0192	0.0200
	0.30	0.047	0.0017	0.0317	0.0324	0.0013	0.0170	0.0173
	0.50	0.043	0.0005	0.0299	0.0304	0.0009	0.0178	0.0181
	0.70	0.042	0.0005	0.0316	0.0321	0.0011	0.0184	0.0190