condition mean min max ZT0-3 3.3 3.3 3.3 ZT4-7 7.1 7.1 7.1 ZT8-11 5.65 5.65 5.65 ZT12-15 8.05 8.05 8.05 ZT16-19 11.5 11.5 11.5 ZT20-23 6.55 6.55 6.55