condition mean min max ZT0-3 2.0807116666666667 1.676915 2.305045 ZT4-7 2.6972899999999997 2.6972899999999997 2.6972899999999997 ZT8-11 2.620485 2.620485 2.620485 ZT12-15 3.0232475 3.001965 3.04453 ZT16-19 3.1656750000000002 3.1656750000000002 3.1656750000000002 ZT20-23 2.29756 2.29756 2.29756