condition mean min max ZT0-3 2.8065433333333334 1.74484 3.8122750000000005 ZT4-7 2.137455 2.137455 2.137455 ZT8-11 2.714305 2.714305 2.714305 ZT12-15 3.7767325 3.6789199999999997 3.8745450000000003 ZT16-19 3.1502299999999996 3.1502299999999996 3.1502299999999996 ZT20-23 4.10777 4.10777 4.10777