condition mean min max ZT0-3 7.671887 7.671887 7.671887 ZT4-7 8.0855175 8.0855175 8.0855175 ZT8-11 7.5615105 7.5615105 7.5615105 ZT12-15 7.5824565 7.5824565 7.5824565 ZT16-19 7.5514765 7.5514765 7.5514765 ZT20-23 7.9168985 7.9168985 7.9168985