condition mean min max ZT0-3 1.920775 1.920775 1.920775 ZT4-7 1.265116 1.265116 1.265116 ZT8-11 1.1718680000000001 1.1718680000000001 1.1718680000000001 ZT12-15 2.10016 2.10016 2.10016 ZT16-19 2.773535 2.773535 2.773535 ZT20-23 2.033045 2.033045 2.033045