condition mean min max ZT0-3 8.602225 8.602225 8.602225 ZT4-7 8.05068 8.05068 8.05068 ZT8-11 6.92661 6.92661 6.92661 ZT12-15 7.3086199999999995 7.3086199999999995 7.3086199999999995 ZT16-19 7.726515 7.726515 7.726515 ZT20-23 7.87083 7.87083 7.87083