span><span class="op">(</span> <span class="va">N</span>, sd<span class="op">=</span><span class="va">sigma</span> <span class="op">)</span>  <span class="co"># abilities</span></span>
<span><span class="co"># item intercepts</span></span>
<span><span class="va">b</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/outer.html" class="external-link">outer</a></span><span class="op">(</span> <span class="fu"><a href="https://rdrr.io/r/base/seq.html" class="external-link">seq<