condition mean min max ZT0-3 17.403697 17.403697 17.403697 ZT4-7 20.5757395 20.5757395 20.5757395 ZT8-11 29.74426 29.74426 29.74426 ZT12-15 25.593334499999997 25.593334499999997 25.593334499999997 ZT16-19 33.6007125 33.6007125 33.6007125 ZT20-23 31.224633500000003 31.224633500000003 31.224633500000003