Different ways to attain the same average treatment effect

Fun draft paper by Andrew Gelman, looking at different patterns of causal effects holding the average treatment effect (ATE) at 0.1 – part-inspired by Anscombe’s (1973) correlation quartet. Each graph shows a correlation between a hypothetical covariate, such as baseline symptom severity, and treatment effect. All four patterns are compatible with the ATE of 0.1.