condition mean min max ZT0-3 7.12588 7.12588 7.12588 ZT4-7 9.18602 9.18602 9.18602 ZT8-11 8.3190805 8.3190805 8.3190805 ZT12-15 8.0205525 8.0205525 8.0205525 ZT16-19 8.923388500000001 8.923388500000001 8.923388500000001 ZT20-23 8.4940925 8.4940925 8.4940925