condition mean min max ZT0-3 5.652016666666667 3.3785100000000003 6.985245000000001 ZT4-7 4.292705 4.292705 4.292705 ZT8-11 6.13702 6.13702 6.13702 ZT12-15 7.3613 7.049495 7.673105 ZT16-19 7.541255 7.541255 7.541255 ZT20-23 8.653555 8.653555 8.653555