Causal Graphs — Drawing What You Believe Causes What
Causal reasoning gets dramatically clearer when you draw it. A causal graph is a diagram of what causes what — nodes for variables, arrows for causal influence — and it turns fuzzy debates about confounding and adjustment into visual rules you can actually check. This post introduces causal graphs (DAGs) and the single most useful thing they do: tell you exactly which variables to control for, and which ones you must leave alone.
Causal reasoning gets clearer when you draw it. A causal graph (DAG) turns fuzzy debates about confounding and adjustment into visual rules: the three building blocks (chain/mediator, fork/confounder, collider) and why 'control for everything' is wrong — adjusting the wrong variable adds bias.