condition mean min max ZT0-3 2.9 2.9 2.9 ZT4-7 3.0 3.0 3.0 ZT8-11 10.25 10.25 10.25 ZT12-15 13.100000000000001 13.100000000000001 13.100000000000001 ZT16-19 21.15 21.15 21.15 ZT20-23 12.75 12.75 12.75