condition mean min max ZT0-3 5.7 5.7 5.7 ZT4-7 2.9 2.9 2.9 ZT8-11 3.5 3.5 3.5 ZT12-15 8.6 8.6 8.6 ZT16-19 7.449999999999999 7.449999999999999 7.449999999999999 ZT20-23 8.75 8.75 8.75