condition mean min max ZT0-3 21.420825 19.87245 22.9692 ZT4-7 16.67905 16.67905 16.67905 ZT8-11 15.3666 15.3666 15.3666 ZT12-15 0 0 0 ZT16-19 18.887900000000002 18.887900000000002 18.887900000000002 ZT20-23 18.74555 18.74555 18.74555