condition mean min max ZT0-3 3.21217 3.21217 3.21217 ZT4-7 1.947485 1.947485 1.947485 ZT8-11 3.1741099999999998 3.1741099999999998 3.1741099999999998 ZT12-15 4.456335 4.456335 4.456335 ZT16-19 6.521459999999999 6.521459999999999 6.521459999999999 ZT20-23 4.700585 4.700585 4.700585