\BeginKnitrBlock{exercise}\iffalse{-91-83-101-108-101-99-116-105-111-110-32-98-105-97-115-93-}\fi{}<div class="exercise"><span class="exercise" id="exr:unnamed-chunk-11"><strong>(\#exr:unnamed-chunk-11)  \iffalse (Selection bias) \fi{} </strong></span>What are some forms of selection bias you may encounter in your own research?</div>\EndKnitrBlock{exercise}