in the slope coefficients, and do not
have a predictor and a response, rather we have two response variables.
So we want to avoid regression to the mean and should look at this as a
multivariate problem, and use principal components analysis (or related
methods) and generalisations designed to compare slopes of several such
axes.</p>
</div>
<div class="section level2">
<h2 id="code-box-13-1-linear-models-of-the-brain-size-body-size-data">Code Box 13.1: Linear models of the brain size-body size data<a class=