condition mean min max ZT0-3 30.799252 30.799252 30.799252 ZT4-7 29.068047 29.068047 29.068047 ZT8-11 29.1752825 29.1752825 29.1752825 ZT12-15 34.348687999999996 34.348687999999996 34.348687999999996 ZT16-19 28.226627999999998 28.226627999999998 28.226627999999998 ZT20-23 31.838615 31.838615 31.838615