condition mean min max ZT0-3 2.496175 2.23459 2.770925 ZT4-7 3.2578500000000004 3.2578500000000004 3.2578500000000004 ZT8-11 2.726645 2.726645 2.726645 ZT12-15 3.5975925 3.49965 3.695535 ZT16-19 2.7544899999999997 2.7544899999999997 2.7544899999999997 ZT20-23 3.74737 3.74737 3.74737