condition mean min max ZT0-3 1.6459996666666667 1.220334 2.037605 ZT4-7 1.54682 1.54682 1.54682 ZT8-11 2.6799150000000003 2.6799150000000003 2.6799150000000003 ZT12-15 6.6197625 6.513525 6.726 ZT16-19 5.7836 5.7836 5.7836 ZT20-23 4.55731 4.55731 4.55731