Models are simplifications and idealizations. As statistician George Box famously noted “all models are wrong, but some are useful” <span class="citation">(Box &amp; Draper, <a href="#ref-Box1987" role="doc-biblioref">1987</a>)</span>. What do we mean by this? Consider the famous London tube map (Figure <a href="intro.html#fig:london-tube-map">1.5</a>). This map is “wrong” because as any map, it is a simplification of reality. It does not provide a completely accurate representation of the world. Bu