condition mean min max ZT0-3 18.112676 18.112676 18.112676 ZT4-7 15.1318995 15.1318995 15.1318995 ZT8-11 16.791683499999998 16.791683499999998 16.791683499999998 ZT12-15 17.405956500000002 17.405956500000002 17.405956500000002 ZT16-19 17.3011925 17.3011925 17.3011925 ZT20-23 16.3937065 16.3937065 16.3937065