condition mean min max ZT0-3 8.33491 8.33491 8.33491 ZT4-7 6.9999199999999995 6.9999199999999995 6.9999199999999995 ZT8-11 6.5789100000000005 6.5789100000000005 6.5789100000000005 ZT12-15 8.446795 8.446795 8.446795 ZT16-19 9.714604999999999 9.714604999999999 9.714604999999999 ZT20-23 9.941095 9.941095 9.941095