condition mean min max ZT0-3 4.137735 3.780595 4.33845 ZT4-7 3.938945 3.938945 3.938945 ZT8-11 3.4590199999999998 3.4590199999999998 3.4590199999999998 ZT12-15 6.93727 6.921945 6.9525950000000005 ZT16-19 6.44139 6.44139 6.44139 ZT20-23 6.264055 6.264055 6.264055