condition mean min max ZT0-3 7.911415 7.911415 7.911415 ZT4-7 8.556778 8.556778 8.556778 ZT8-11 9.037912 9.037912 9.037912 ZT12-15 7.414682 7.414682 7.414682 ZT16-19 8.1404175 8.1404175 8.1404175 ZT20-23 7.867903 7.867903 7.867903