condition mean min max ZT0-3 2.2036716666666667 1.47373 2.721235 ZT4-7 1.392925 1.392925 1.392925 ZT8-11 1.7024750000000002 1.7024750000000002 1.7024750000000002 ZT12-15 2.2953025 2.1843 2.4063049999999997 ZT16-19 3.2416150000000004 3.2416150000000004 3.2416150000000004 ZT20-23 3.4874099999999997 3.4874099999999997 3.4874099999999997