The growing interest in integrating causal inference and Design Theory

Stephen maybe this will help explain the difference between HTE caused by covariate vector and the effect of RCT gate generated causal system mixing which I call “Synthetic Heterogeneity”.

This phenomenon is fundamentally:

• Not → Second Layer (Classic Fisher-Hill RCT) (Variation of treatment effect within a disease) → τᵢ(xᵢ)

• Instead → Third Layer (RCT with synthetic gate) The generation of (and variation in) the causal system mix (which diseases are present) → πᵢ(S=1)

This causes the “cause mixture paradox” (Below from the above reference) and the unsafe transport of RCT to clinical guidelines we have observed for decades in critical care where this third layer is generated. Is the difference clear?

This mis interpretation of Layer 3 for Layer 2 is what caused the RCT (meta-analysis) derived ventilator guideline disaster during the COVID pandemic. Those guidelines have been abandoned but the cause of the RCT failure was not investigated. Trialists now have to step their cognitive understanding of trial structure up to prevent similar patient harm in the future.