condition mean min max ZT0-3 2.5 2.5 2.5 ZT4-7 3.3 3.3 3.3 ZT8-11 18.450000000000003 18.450000000000003 18.450000000000003 ZT12-15 3.1999999999999997 3.1999999999999997 3.1999999999999997 ZT16-19 5.5 5.5 5.5 ZT20-23 15.4 15.4 15.4