<span> r+5 </span><span>r^2+4r-21
</span><span>-------------- / --------------------
r^2+5r-14 </span><span>r-2
</span> r+5 r-2
= -------------- x --------------------
r^2+5r-14 r^2+4r-21
r+5 r-2
= -------------- x --------------------
(r+7)(r-2) (r+7)(r-3)
r+5
= -----------------
(r+7)^2 (r-3)
Answer: This does not represent an SRS because each group of patients chosen does not have an equally likely chance of being chosen.