><p>A vector indicating the columns containing the groups.</p></dd>

</dl></div>
    <div id="value">
    <h2>Value</h2>
    <p>df the degrees of freedom rectified according to Welch (1947).</p>
    </div>
    <div id="references">
    <h2>References</h2>
    <p>Welch BL (1947).
“The generalization of student's' problem when several different population variances are involved.”
<em>Biometrika</em>, <b>34</b>(1/2), 28–35.
<a href="https://doi.org/10.1093/biomet/34.1-2.28" class="external-link">doi:10.1