Table 2.

α-error spending and power at each interim analysis for determination of non-inferiority

Interim analysis	Z-value upper bound	α-error spending	Power
1	3.47	0.00026	0.014
2	2.45	0.00697	0.241
3	2.00	0.01795	0.329
4	1.73	0.02482	0.216
Total		0.05	0.80