Monte Carlo Power Analysis for Small-System A/B Trials

Michael D. Ekstrand, Daniel Kluver, Karl Higley, and Bart P. Knijnenburg. 2026. Monte Carlo Power Analysis for Small-System A/B Trials. To appear in Proceedings of the 20th ACM Conference on Recommender Systems (Research and Practice Notes), Sep 28–Oct 2, 2026. 2 pp. DOI 10.1145/3773078.3841270.

Diagram of experiment design.
Diagram of experiment design (Fig. 1).

Abstract

Good experimental practice and predicting the scientific usefulness of an experiment or experimental platform require power analysis: estimating, a priori, how likely the experiment is to detect the intended effect if indeed it exists. While simple experimental designs admit well-understood power analysis methods, more sophisticated experimental designs and settings often require bespoke techniques to avoid either over- or under-estimating experimental power. We present the Monte Carlo method we use to estimate the power of experiments intended to increase user engagement with personalized e-mail newsletters of recommended news articles.