condition mean min max ZT0-3 8.242215 8.242215 8.242215 ZT4-7 7.994669999999999 7.994669999999999 7.994669999999999 ZT8-11 7.3423035 7.3423035 7.3423035 ZT12-15 7.319745 7.319745 7.319745 ZT16-19 7.619619 7.619619 7.619619 ZT20-23 7.646142 7.646142 7.646142