condition mean min max ZT0-3 7.432545 7.432545 7.432545 ZT4-7 7.9608585000000005 7.9608585000000005 7.9608585000000005 ZT8-11 8.011232 8.011232 8.011232 ZT12-15 7.5059535 7.5059535 7.5059535 ZT16-19 7.4206395 7.4206395 7.4206395 ZT20-23 8.384803 8.384803 8.384803