ropriate DAG.</p>
<p>If our data include only X and Y, the situation is hopeless. A non-zero coefficient for the <code>Y ~ X</code> model might be the result of a causal path from X to Y, or a causal path from Y to X, or even a correlating pathway between X and Y mediated by some other variable C (or multiple other variables, C, D, E, etc.). Similarly, a zero coefficient for the <code>Y ~ X</code> model is no guarantee that there is no causal connection between them.</p>
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