der-section-number">1.9</span> Hierarchical Logistic Regression</h2>
<p>The simplest multilevel model is a hierarchical model in which the
data are grouped into <span class="math inline">\(L\)</span> distinct categories (or levels). An extreme
approach would be to completely pool all the data and estimate a
common vector of regression coefficients <span class="math inline">\(\beta\)</span>. At the other
extreme, an approach with no pooling assigns each level <span class="math inline">\(l\)</span> its own
co