condition mean min max ZT0-3 6.6 6.6 6.6 ZT4-7 5.8 5.8 5.8 ZT8-11 5.65 5.65 5.65 ZT12-15 3.8000000000000003 3.8000000000000003 3.8000000000000003 ZT16-19 18.049999999999997 18.049999999999997 18.049999999999997 ZT20-23 7.5 7.5 7.5