Chapter 4. Decision Theoretic Approaches to Experiment Design and External Validity

A modern, decision-theoretic framework can help clarify important practical questions of experimental design. Building on our recent work, this chapter begins by summarizing our framework for understanding the goals of experimenters and applying this to rerandomization. We then use this framework to shed light on questions related to experimental registries, preanalysis plans, and most importantly, external validity. Our framework implies that even when large samples can be collected, external decision-making remains inherently subjective. We embrace this conclusion and argue that in order to improve external validity, experimental research needs to create a space for structured speculation.