condition mean min max ZT0-3 6.75 6.75 6.75 ZT4-7 2.4 2.4 2.4 ZT8-11 6.7 6.7 6.7 ZT12-15 4.0 4.0 4.0 ZT16-19 2.6 2.6 2.6 ZT20-23 5.4 5.4 5.4