condition mean min max ZT0-3 4.356865 4.356865 4.356865 ZT4-7 3.1816950000000004 3.1816950000000004 3.1816950000000004 ZT8-11 3.67341 3.67341 3.67341 ZT12-15 4.232559999999999 4.232559999999999 4.232559999999999 ZT16-19 4.2853200000000005 4.2853200000000005 4.2853200000000005 ZT20-23 4.292425 4.292425 4.292425