condition mean min max ZT0-3 8.008998333333334 2.5460000000000003 11.246305 ZT4-7 2.783225 2.783225 2.783225 ZT8-11 2.51466 2.51466 2.51466 ZT12-15 3.8789149999999997 3.64741 4.1104199999999995 ZT16-19 5.5491399999999995 5.5491399999999995 5.5491399999999995 ZT20-23 10.048895 10.048895 10.048895