condition mean min max ZT0-3 6.8 6.8 6.8 ZT4-7 4.2 4.2 4.2 ZT8-11 8.55 8.55 8.55 ZT12-15 16.9 16.9 16.9 ZT16-19 6.800000000000001 6.800000000000001 6.800000000000001 ZT20-23 3.5 3.5 3.5