condition mean min max ZT0-3 2.237425 2.237425 2.237425 ZT4-7 4.35988 4.35988 4.35988 ZT8-11 3.01816 3.01816 3.01816 ZT12-15 2.325695 2.325695 2.325695 ZT16-19 2.05092 2.05092 2.05092 ZT20-23 2.137755 2.137755 2.137755