Table 2. Operating characteristics.

Scenario 1: Arm B vs. A: 40% versus 20%		Arm B
	Probability	fail in stage 1	fail in stage 2	pass stage 2
Arm A	fail in stage 1	0.03	0.03	0.5
	fail in stage 2	0.02	0.02	0.32
	pass stage 2	0	0	0.09
Both arms passing the 2nd stage: 9%. Among them, Arm B claims 4.09% as winner. Overall power of Arm B= 86%.

Scenario 2: Arm B vs. A: 35% versus 20%		Arm B
	Probability	fail in stage 1	fail in stage 2	pass stage 2
Arm A	fail in stage 1	0.06	0.07	0.42
	fail in stage 2	0.04	0.05	0.27
	pass stage 2	0.01	0.01	0.07
Both arms passing the 2nd stage: 7%. Among them, Arm B claims 2.12% as winner. Overall power of Arm B= 71%.

Scenario 3: Arm B vs. A: 40% versus 25%		Arm B
	Probability	fail in stage 1	fail in stage 2	pass stage 2
Arm A	fail in stage 1	0.02	0.02	0.32
	fail in stage 2	0.02	0.02	0.33
	pass stage 2	0.01	0.01	0.26
Both arms passing the 2nd stage: 26%. Among them, Arm B claims 10.79% as winner. Overall power of Arm B= 75%.

Scenario 4: Arm B vs. A: 20% versus 20%		Arm B
	Probability	fail in stage 1	fail in stage 2	pass stage 2
Arm A	fail in stage 1	0.3	0.2	0.05
	fail in stage 2	0.19	0.13	0.03
	pass stage 2	0.05	0.03	0.01
Both arms passing the 2nd stage: 1%. Among them, Arm B claims 0.01% as winner. Type I error= 8.73%.