condition mean min max ZT0-3 15.439848 15.439848 15.439848 ZT4-7 17.121779 17.121779 17.121779 ZT8-11 14.5528885 14.5528885 14.5528885 ZT12-15 16.107670499999998 16.107670499999998 16.107670499999998 ZT16-19 18.877110000000002 18.877110000000002 18.877110000000002 ZT20-23 14.7537205 14.7537205 14.7537205