condition mean min max ZT0-3 3.147865 3.147865 3.147865 ZT4-7 3.0166899999999996 3.0166899999999996 3.0166899999999996 ZT8-11 2.989805 2.989805 2.989805 ZT12-15 2.36581 2.36581 2.36581 ZT16-19 2.535525 2.535525 2.535525 ZT20-23 2.452385 2.452385 2.452385