n>
<span><span class="co"># apply cluster-robust inference methods (robust variance estimation)</span></span>
<span><span class="co"># note: use the improved methods from the clubSandwich package</span></span>
<span><span class="va">sav</span> <span class="op">&lt;-</span> <span class="fu"><a href="../reference/robust.html">robust</a></span><span class="op">(</span><span class="va">res</span>, cluster <span class="op">=</span> <span class="va">...</span>, clubSandwich <span class="op">=</span> <span class="