condition mean min max ZT0-3 15.6 15.6 15.6 ZT4-7 2.9 2.9 2.9 ZT8-11 3.8 3.8 3.8 ZT12-15 2.55 2.55 2.55 ZT16-19 4.6 4.6 4.6 ZT20-23 6.75 6.75 6.75