condition mean min max ZT0-3 5.545885 5.545885 5.545885 ZT4-7 3.83493 3.83493 3.83493 ZT8-11 6.19178 6.19178 6.19178 ZT12-15 6.43143 6.43143 6.43143 ZT16-19 7.389475 7.389475 7.389475 ZT20-23 5.25475 5.25475 5.25475