condition mean min max ZT0-3 7.118615 7.118615 7.118615 ZT4-7 5.90081 5.90081 5.90081 ZT8-11 6.3178 6.3178 6.3178 ZT12-15 7.75381 7.75381 7.75381 ZT16-19 7.771725 7.771725 7.771725 ZT20-23 7.695385 7.695385 7.695385