condition mean min max ZT0-3 18.802994 18.802994 18.802994 ZT4-7 19.6441885 19.6441885 19.6441885 ZT8-11 21.9180315 21.9180315 21.9180315 ZT12-15 20.4847805 20.4847805 20.4847805 ZT16-19 22.470888000000002 22.470888000000002 22.470888000000002 ZT20-23 19.6950385 19.6950385 19.6950385