condition mean min max ZT0-3 8.497060000000001 8.497060000000001 8.497060000000001 ZT4-7 5.8347750000000005 5.8347750000000005 5.8347750000000005 ZT8-11 4.471905 4.471905 4.471905 ZT12-15 6.52722 6.52722 6.52722 ZT16-19 8.13005 8.13005 8.13005 ZT20-23 8.905095 8.905095 8.905095