condition mean min max ZT0-3 2.617113333333333 1.650055 3.33647 ZT4-7 2.1125495 2.1125495 2.1125495 ZT8-11 3.873055 3.873055 3.873055 ZT12-15 2.2082375 1.76312 2.6533550000000004 ZT16-19 3.02256 3.02256 3.02256 ZT20-23 3.12409 3.12409 3.12409