pan class="arithmatex">\(\textbf{y}\)</span>, and we have an additional <span class="arithmatex">\(p-q\)</span> predictors in the matrix <span class="arithmatex">\(\textbf{X}_2\)</span>. Denote the current residual by <span class="arithmatex">\(\textbf{r}\)</span>. We wish to establish which one of these additional variables will reduce the residual sum-of-squares the most when included with those in <span class="arithmatex">\(\textbf{X}_1\)</span>. Describe an efficient procedure for doing this.</p>
</deta