condition mean min max ZT0-3 4.2 4.2 4.2 ZT4-7 1.6 1.6 1.6 ZT8-11 5.85 5.85 5.85 ZT12-15 3.3 3.3 3.3 ZT16-19 2.4000000000000004 2.4000000000000004 2.4000000000000004 ZT20-23 3.1999999999999997 3.1999999999999997 3.1999999999999997