Nathan was an expert on developing decision trees for his company. After developing one tree, a colleague asked Nathan what the Rel Error represented in the data below. Nathan said $...$

Level CP Num Splits Rel Error X Error X Std Dev

$10\mathrm{.}5001\mathrm{.}001\mathrm{.}170\mathrm{.}050735$

$20\mathrm{.}4410\mathrm{.}500\mathrm{.}730\mathrm{.}061215$

$30\mathrm{.}0020\mathrm{.}060\mathrm{.}100\mathrm{.}030551$