condition mean min max ZT0-3 4.054403333333333 1.283175 5.96502 ZT4-7 1.212873 1.212873 1.212873 ZT8-11 1.287395 1.287395 1.287395 ZT12-15 2.2582575 1.95452 2.561995 ZT16-19 2.4355599999999997 2.4355599999999997 2.4355599999999997 ZT20-23 3.98836 3.98836 3.98836