ht)^2.
\]</span> To put the error back on the scale of the original value, the square root may be applied, resulting in what is known prosaically as <em>root mean square error</em> (RMSE), <span class="math display">\[
\textrm{rmse} = \sqrt{\textrm{mean-sq-err}}.
\]</span></p>
</section>
<section id="predictive-estimates-in-stan" class="level3 unnumbered">
<h3 class="unnumbered anchored" data-anchor-id="predictive-estimates-in-stan">Predictive estimates in Stan</h3>
<p>Consider a simple linear regression mo