condition mean min max ZT0-3 2.191675 2.191675 2.191675 ZT4-7 2.5306949999999997 2.5306949999999997 2.5306949999999997 ZT8-11 1.6535 1.6535 1.6535 ZT12-15 1.52925 1.52925 1.52925 ZT16-19 2.591195 2.591195 2.591195 ZT20-23 1.982185 1.982185 1.982185