condition mean min max ZT0-3 3.1 3.1 3.1 ZT4-7 5.5 5.5 5.5 ZT8-11 18.0 18.0 18.0 ZT12-15 11.6 11.6 11.6 ZT16-19 3.5999999999999996 3.5999999999999996 3.5999999999999996 ZT20-23 6.449999999999999 6.449999999999999 6.449999999999999