condition mean min max ZT0-3 14.540879 14.540879 14.540879 ZT4-7 12.9167495 12.9167495 12.9167495 ZT8-11 15.681107999999998 15.681107999999998 15.681107999999998 ZT12-15 13.038174 13.038174 13.038174 ZT16-19 16.493886 16.493886 16.493886 ZT20-23 15.620429 15.620429 15.620429