condition mean min max ZT0-3 7.671887 7.671887 7.671887 ZT4-7 7.5693175 7.5693175 7.5693175 ZT8-11 6.715406 6.715406 6.715406 ZT12-15 7.889908500000001 7.889908500000001 7.889908500000001 ZT16-19 7.3421895 7.3421895 7.3421895 ZT20-23 8.184506 8.184506 8.184506