#polytree

Question 1: Single choice

mediumAI-checkedProbabilistic & Graphical Models

A DAG over $x_1, \ldots, x_6$ has the edges $x_1 \to x_3$ , $x_1 \to x_4$ , $x_2 \to x_4$ , $x_4 \to x_5$ and $x_4 \to x_6$ (a polytree: no loops, but $x_4$ has two parents). Compare its moral graph with its factor graph, which has one factor node per conditional $p(x_i \mid \mathrm{pa}_i)$ . Which statement is correct?

Both contain a loop through $x_1$ , $x_2$ and $x_4$ 1
Neither contains a loop, because the DAG is a polytree2
The moral graph contains a loop, while the factor graph is still a tree3
The factor graph has a loop, while the moral graph is a tree4

Timed test