condition mean min max ZT0-3 3.622165 3.622165 3.622165 ZT4-7 3.23233 3.23233 3.23233 ZT8-11 3.6996149999999997 3.6996149999999997 3.6996149999999997 ZT12-15 4.282555 4.282555 4.282555 ZT16-19 3.9994250000000005 3.9994250000000005 3.9994250000000005 ZT20-23 3.726325 3.726325 3.726325