condition mean min max ZT0-3 2.6 2.6 2.6 ZT4-7 3.7 3.7 3.7 ZT8-11 4.35 4.35 4.35 ZT12-15 3.8000000000000003 3.8000000000000003 3.8000000000000003 ZT16-19 3.8 3.8 3.8 ZT20-23 3.1 3.1 3.1