\BeginKnitrBlock{exercise}\iffalse{-91-85-110-100-101-114-115-116-97-110-100-105-110-103-32-121-111-117-114-32-100-97-116-97-93-}\fi{}<div class="exercise"><span class="exercise" id="exr:unnamed-chunk-108"><strong>(\#exr:unnamed-chunk-108)  \iffalse (Understanding your data) \fi{} </strong></span>Explain why it's easy to guess these things.</div>\EndKnitrBlock{exercise}