condition mean min max ZT0-3 17.904675 17.89835 17.911 ZT4-7 6.504485 6.504485 6.504485 ZT8-11 3.814895 3.814895 3.814895 ZT12-15 0 0 0 ZT16-19 20.863500000000002 20.863500000000002 20.863500000000002 ZT20-23 29.98235 29.98235 29.98235