condition mean min max ZT0-3 5.264616666666667 3.8657399999999997 6.260625 ZT4-7 3.9159949999999997 3.9159949999999997 3.9159949999999997 ZT8-11 3.9577799999999996 3.9577799999999996 3.9577799999999996 ZT12-15 7.54021 7.021509999999999 8.058910000000001 ZT16-19 8.32795 8.32795 8.32795 ZT20-23 9.25182 9.25182 9.25182