condition mean min max ZT0-3 2.031955 2.031955 2.031955 ZT4-7 3.610035 3.610035 3.610035 ZT8-11 2.034475 2.034475 2.034475 ZT12-15 1.6666699999999999 1.6666699999999999 1.6666699999999999 ZT16-19 1.683015 1.683015 1.683015 ZT20-23 1.75375 1.75375 1.75375