~ drug</code> and check whether the effect size of <code>drug</code> on <code>mortality</code> is positive (harmful drug!) or negative (drug reduces mortality).</p>
<p>Our intention with <code>mortality ~ drug</code> is to probe the direct causal link between <code>drug</code> and <code>mortality</code>. But will we achieve our intention with the model <code>mortality ~ drug</code>? There is a difficulty in this example: the direct <code>drug</code><span class="math inline">\(\rightarrow\)</span><code>morta