condition mean min max ZT0-3 16.812725 16.4346 17.19085 ZT4-7 13.35885 13.35885 13.35885 ZT8-11 12.10145 12.10145 12.10145 ZT12-15 0 0 0 ZT16-19 16.23525 16.23525 16.23525 ZT20-23 16.25505 16.25505 16.25505