condition mean min max ZT0-3 1.7 1.7 1.7 ZT4-7 6.8 6.8 6.8 ZT8-11 45.15 45.15 45.15 ZT12-15 4.8500000000000005 4.8500000000000005 4.8500000000000005 ZT16-19 18.75 18.75 18.75 ZT20-23 22.1 22.1 22.1