offer-westort_coppock_green_2021

Adaptive Experimental Design: Prospects and Applications in Political Science

Offer-Westort, Molly, Alexander Coppock, and Donald P. Green. 2021. American Journal of Political Science 65(4): 826–844. doi:10.1111/ajps.12597

Experimental researchers in political science frequently face the problem of inferring which of several treatment arms is most effective. They may also seek to estimate mean outcomes under that arm, construct confidence intervals, and test hypotheses. Ordinarily, multi-arm trials conducted using static designs assign participants to each arm with fixed probabilities. However, a growing statistical literature suggests that adaptive experimental designs that dynamically allocate larger assignment probabilities to more promising treatments are better equipped to discover the best-performing arm. Using simulations and empirical applications, we explore the conditions under which such designs hasten the discovery of superior treatments and improve the precision with which their effects are estimated. Recognizing that many scholars seek to assess performance relative to a control condition, we also develop and implement a novel adaptive algorithm that seeks to maximize the precision with which the largest treatment effect is estimated.

offer-westort_coppock_green_2021
FIGURE 3 from paper: Study 1, Over Time Posterior Probabilities Posterior probability of being the best arm Minimum wage Right−to−work 1.00 Proposal 4 (BM) Proposal 3 (N) 0.75 Proposal 4 (Y) Proposal 4 (CA) Proposal 5 (Y) 0.50 Proposal 3 (Y) Proposal 2 (BM)