condition mean min max ZT0-3 9.439174 9.439174 9.439174 ZT4-7 8.818106 8.818106 8.818106 ZT8-11 9.65313 9.65313 9.65313 ZT12-15 8.629024 8.629024 8.629024 ZT16-19 7.9743995000000005 7.9743995000000005 7.9743995000000005 ZT20-23 9.0465845 9.0465845 9.0465845