Table 3 Four functions applied to define the thresholds at each of the interim analyses

1

A uniform function: \(\tau ^{l}_{j} = \tau *^{11}_{j}\) for all l∈(1,11).

2

A linear function: \(\tau ^{l}_{j} = a \times l + b\),

3

A linear function with an exponential transformation: \(\tau ^{l}_{j} = a \times exp^{l} + b\),

4

A linear function with a logarithm transformation: \(\tau ^{l}_{j} = a \times log(l) + b\).