A Two-Part Machine Learning Approach to Characterizing Network Interference in A/B Testing

The reliability of controlled experiments, or "A/B tests," can often be compromised due to the phenomenon of network interference, wherein the outcome for one unit is influenced by other units. To tackle this challenge, we propose a machine learning-based method to identify and characterize heterogeneous network interference. Our approach accounts for latent complex network structures and automates the task of "exposure mapping'' determination, which addresses the two major limitations in the existing literature. We introduce "causal network motifs'' and employ transparent machine learning models to establish the most suitable exposure mapping that reflects underlying network interference patterns. Our method's efficacy has been validated through simulations on two synthetic experiments and a real-world, large-scale test involving 1-2 million Instagram users, outperforming conventional methods such as design-based cluster randomization and analysis-based neighborhood exposure mapping. Overall, our approach not only offers a comprehensive, automated solution for managing network interference and improving the precision of A/B testing results, but it also sheds light on users' mutual influence and aids in the refinement of marketing strategies.