="math inline">\(k\)</span>-fold
cross-validation, take note of the column names. While your
<code>data.frame</code> you pass in to <code>repkfold_ttest</code> can
have more than the four columns specified here, it <strong>must</strong>
contain at least these four with the exact corresponding names. The
function explicitly searches for them. They are:</p>
<ol style="list-style-type: decimal">
<li>
<code>"model"</code> — contains a label for each of the two models
to compare</li>
<li>
<code>"values"</code>