condition mean min max ZT0-3 8.207992 8.207992 8.207992 ZT4-7 9.213692 9.213692 9.213692 ZT8-11 8.294507 8.294507 8.294507 ZT12-15 7.884043500000001 7.884043500000001 7.884043500000001 ZT16-19 8.1248865 8.1248865 8.1248865 ZT20-23 8.542624499999999 8.542624499999999 8.542624499999999