or Ava’s results refute Cleo’s hypothesis that there is no connection between X and Y. But models, on their own, are powerless to show the direction of influence.</p>
<div class="page-columns page-full"><p>For more than a century, many statisticians did not carry the issue beyond the simple <span class="math inline">\(Y \leftrightarrow X\)</span> example. It became dogma that the only way to establish causation is to experiment, that is, for the researcher to intervene in the system to sever causal infl