putationally intensive and the resulting residuals are often unreliable due to small group sizes.</p>
</div>
<div id="na-action-and-data" class="section level3">
<h3 class="hasAnchor">
<a href="#na-action-and-data" class="anchor"></a>na.action and data</h3>
<p>The final parameter, <code>data</code>, is an argument that becomes required when <code>na.action = na.exclude</code> for an <code>lmerMod</code> model object. Model frames in <code>lme4</code> always use <code>na.omit</code>. Thus, a <code>data</code