. Author manuscript; available in PMC: 2014 Mar 15.

Published in final edited form as: Stat Med. 2012 Sep 4;32(6):899–913. doi: 10.1002/sim.5597

Table 2.

Cumulative type I error rates for Gray's test applied in a group sequential setting, with an O'Brien-Fleming type error spending function, n = 100 per group, and an additional 10% nonadministrative censoring.

(A,T)	p	(γ₁, γ₂)	Cumulative type I error by interim look
(A,T)	p	(γ₁, γ₂)	1	2	3	4
(1,1.61)	0.25	(1,1)	0.000	0.005	0.021	0.047
		(1,1.5)	0.000	0.005	0.021	0.050
		(1.5,1.5)	0.001	0.004	0.019	0.050

	0.5	(1,1)	0.001	0.006	0.020	0.047
		(1,1.5)	0.001	0.007	0.022	0.048
		(1.5,1.5)	0.000	0.006	0.021	0.049

	0.75	(1,1)	0.001	0.006	0.022	0.048
		(1,1.5)	0.001	0.007	0.024	0.051
		(1.5,1.5)	0.001	0.004	0.020	0.048

(2.3,2.5)	0.25	(1,1)	0.000	0.006	0.020	0.051
		(1,1.5)	0.000	0.006	0.021	0.048
		(1.5,1.5)	0.000	0.004	0.0205	0.047

	0.5	(1,1)	0.001	0.007	0.022	0.047
		(1,1.5)	0.001	0.006	0.021	0.047
		(1.5,1.5)	0.000	0.005	0.020	0.050

	0.75	(1,1)	0.001	0.005	0.022	0.048
		(1,1.5)	0.001	0.006	0.022	0.050
		(1.5,1.5)	0.001	0.006	0.020	0.049