condition mean min max ZT0-3 9.430942 9.430942 9.430942 ZT4-7 9.540076 9.540076 9.540076 ZT8-11 8.3773295 8.3773295 8.3773295 ZT12-15 9.291890500000001 9.291890500000001 9.291890500000001 ZT16-19 10.597522 10.597522 10.597522 ZT20-23 13.466457 13.466457 13.466457