><span class="op">(</span><span class="va">formula</span>, <span class="va">data</span><span class="op">)</span></span>
<span><span class="op">}</span></span></code></pre></div>
<div class="section level3">
<h3 id="setting-up-specifications">Setting up specifications<a class="anchor" aria-label="anchor" href="#setting-up-specifications"></a>
</h3>
<p>We can now use these function to estimate these models. In this
example, we investigate the influence of different nesting structures on
the fixed effect betwe