condition mean min max ZT0-3 6.099985 6.099985 6.099985 ZT4-7 4.937585 4.937585 4.937585 ZT8-11 4.82593 4.82593 4.82593 ZT12-15 4.802595 4.802595 4.802595 ZT16-19 6.46612 6.46612 6.46612 ZT20-23 5.618525 5.618525 5.618525