condition mean min max ZT0-3 6.0 6.0 6.0 ZT4-7 5.9 5.9 5.9 ZT8-11 3.5 3.5 3.5 ZT12-15 4.15 4.15 4.15 ZT16-19 7.4 7.4 7.4 ZT20-23 4.65 4.65 4.65