condition mean min max ZT0-3 3.876975 3.876975 3.876975 ZT4-7 2.753575 2.753575 2.753575 ZT8-11 3.747845 3.747845 3.747845 ZT12-15 4.59274 4.59274 4.59274 ZT16-19 5.571835 5.571835 5.571835 ZT20-23 4.098725 4.098725 4.098725