condition mean min max ZT0-3 6.699999999999999 6.699999999999999 6.699999999999999 ZT4-7 4.3 4.3 4.3 ZT8-11 14.8 14.8 14.8 ZT12-15 7.449999999999999 7.449999999999999 7.449999999999999 ZT16-19 12.5 12.5 12.5 ZT20-23 6.75 6.75 6.75