condition mean min max ZT0-3 18.885550000000002 18.885550000000002 18.885550000000002 ZT4-7 16.4649 16.4649 16.4649 ZT8-11 17.3192 17.3192 17.3192 ZT12-15 20.921458333333334 20.921458333333334 20.921458333333334 ZT16-19 21.618275 21.618275 21.618275 ZT20-23 21.901825 21.901825 21.901825