Fig. 1.

Diagram of the proposed moving-reference adaptive randomization for a three-arm trial. The top panels, from left to right, show that we first obtain posterior distributions of p₁, p₂, p₃ and p̄; then calculate R_k = pr(p_k > p̄|D) for k = 1, 2, 3; and assign the arm with the smallest value of R_k (i.e., arm 1) a randomization probability π₁. After spending π₁, we remove arm 1 from the comparison set and distribute the remaining randomization probability to the remaining arms (i.e, arms 1 and 2) in a similar manner, as demonstrated in the bottom panels.