condition mean min max ZT0-3 12.564325 12.1768 12.95185 ZT4-7 7.818645 7.818645 7.818645 ZT8-11 9.4919 9.4919 9.4919 ZT12-15 0 0 0 ZT16-19 15.9581 15.9581 15.9581 ZT20-23 23.571399999999997 23.571399999999997 23.571399999999997