Fig. 1

Effect of the choice of the design parameters ε and δ in BARTA on the number of patients allocated to the experimental treatment and on the total number of treatment successes. Cumulative distribution functions of N₁(200) (top) and S(200) (bottom) are shown, based on 5000 simulated data sets, under \(\mathbb {Q}_{null}\) with true parameter values θ₀=θ₁=0.3 and \(\mathbb {Q}_{alt}\) with values θ₀=0.3,θ₁=0.5. Three combinations of the design parameters were used: (a) ε=0.1,δ=0.1, (b) ε=0.05,δ=0.1, (c) ε=0.2,δ=0.05. In addition, (d) represents a completely symmetric treatment allocation. For comparison we also plot the corresponding CDF under the alternative hypothesis obtained by using fractional Thompson’s rule with respective parameters κ=0.25,0.5,0.75 and 1