condition mean min max ZT0-3 7.671887 7.671887 7.671887 ZT4-7 8.1495145 8.1495145 8.1495145 ZT8-11 7.7031845 7.7031845 7.7031845 ZT12-15 7.512404500000001 7.512404500000001 7.512404500000001 ZT16-19 7.764263 7.764263 7.764263 ZT20-23 8.401816 8.401816 8.401816