The growing interest in integrating causal inference and Design Theory

stephenrho:

In a randomized experiment it is not possible for X to cause treatment selection, which I would take from X → T in a conventional DAG.

I realize I never answered this point. The statement that this is a RCT DAG makes treatment assignment by randomization. This step in the graph is omitted as shorthand. X here is the disease agnostic gate, a threshold of nonspecific severity values. So X besides being a selection gate is actually also a covariate for each of the different diseases it selects.

There