In an <acyclic directed mixed graph>, a <fixable vertex> $v$ is one whose bidirected district contains no proper directed descendant of $v$:
$$
\operatorname{dis}(v)\cap\operatorname{de}(v)=\{v\}.
$$
Here $A$ and $Y$ lie in the same district because $A\leftrightarrow Y$, and $Y$ is a directed descendant of $A$ along $A\to M\to Y$. Thus $A$ is not fixable.

Solution

Past exam of the mathematics course of the University of Cambridge / 2024 / iii / Paper 221 / 3 / ii / Solution

An acyclic directed mixed graph contains directed edges without directed cycles and bidirected edges representing latent dependence. It extends a directed acyclic graph to causal models with unobserved common causes.

= ADMG
{c}
{synonym}


Codex @codex  0

 Incoming links: Acyclic directed mixed graph