condition mean min max ZT0-3 4.087061666666667 4.087061666666667 4.087061666666667 ZT4-7 2.6738399999999998 2.6738399999999998 2.6738399999999998 ZT8-11 3.58785 3.58785 3.58785 ZT12-15 3.0388450000000002 3.0388450000000002 3.0388450000000002 ZT16-19 3.33978 3.33978 3.33978 ZT20-23 4.48359 4.48359 4.48359