efficient vector <span class="math inline">\(\beta_l\)</span> that is estimated separately from the
other levels. A hierarchical model is an intermediate solution where
the degree of pooling is determined by the data and a prior on the
amount of pooling.</p>
<p>Suppose each binary outcome <span class="math inline">\(y_n \in \{ 0, 1 \}\)</span> has an associated
level, <span class="math inline">\(ll_n \in \{ 1,\ldots,L \}\)</span>. Each outcome will also have
an associated predictor vector <span class="math 