condition mean min max ZT0-3 14.649999999999999 14.649999999999999 14.649999999999999 ZT4-7 3.9 3.9 3.9 ZT8-11 6.8 6.8 6.8 ZT12-15 4.449999999999999 4.449999999999999 4.449999999999999 ZT16-19 6.0 6.0 6.0 ZT20-23 12.15 12.15 12.15