condition mean min max ZT0-3 21.1 21.1 21.1 ZT4-7 3.3 3.3 3.3 ZT8-11 6.8 6.8 6.8 ZT12-15 7.550000000000001 7.550000000000001 7.550000000000001 ZT16-19 6.6 6.6 6.6 ZT20-23 6.95 6.95 6.95