condition mean min max ZT0-3 8.9 8.9 8.9 ZT4-7 2.6 2.6 2.6 ZT8-11 4.25 4.25 4.25 ZT12-15 2.05 2.05 2.05 ZT16-19 17.700000000000003 17.700000000000003 17.700000000000003 ZT20-23 21.5 21.5 21.5