mates</h3>
<p>In addition to parameters, other unknown quantities may be estimated, such as the score of a football match or the effect of a medical treatment given to a subject. In these cases, square error is defined in the same way. If there are multiple exchangeable outcomes being estimated, <span class="math inline">\(z_1, \ldots, z_N,\)</span> then it is common to report <em>mean square error</em> (MSE), <span class="math display">\[
\textrm{mse}
= \frac{1}{N} \sum_{n = 1}^N \left( \hat{z}_n - z_n\rig