Table 6.

Operating characteristics of the group sequential designs in the systemic sclerosis example. The average sample number and conjunctive power are computed for δ _A/σ = δ _B/σ = 0.4. The maximum sample size N is chosen such that the disjunctive power is 80% given δ _A/σ = 0.4, δ _B=0. The rejection and futility boundaries are optimized as in Section 4.

	Boundaries					Sample size				Power
Design	u 1	u 2	l 1	v 1	v 2	$\overline{\mathrm{ASN}}$	H 1	H 0	N	conj.	disj.
Sep.	2.64	2.30	0.94	2.09	2.30	265	295	235	390	0.70	0.91
Sim.	2.51	2.35	0.97	2.10	2.28	256	272	239	402	0.58	0.92
Imp.	2.52	2.35	0.97	1.99	2.07	256	272	239	402	0.64	0.92