condition mean min max ZT0-3 2.2 2.2 2.2 ZT4-7 2.1 2.1 2.1 ZT8-11 2.3 2.3 2.3 ZT12-15 1.5499999999999998 1.5499999999999998 1.5499999999999998 ZT16-19 3.3499999999999996 3.3499999999999996 3.3499999999999996 ZT20-23 1.4 1.4 1.4