\BeginKnitrBlock{exercise}\iffalse{-91-84-121-112-101-115-32-111-102-32-98-105-97-115-93-}\fi{}<div class="exercise"><span class="exercise" id="exr:unnamed-chunk-10"><strong>(\#exr:unnamed-chunk-10)  \iffalse (Types of bias) \fi{} </strong></span>Some specific forms of selection bias are _survivorship bias_, _self--selection bias_, _non--response bias_. Can you imagine what these terms mean? </div>\EndKnitrBlock{exercise}