condition mean min max ZT0-3 2.875705 2.875705 2.875705 ZT4-7 2.6535450000000003 2.6535450000000003 2.6535450000000003 ZT8-11 3.5018599999999998 3.5018599999999998 3.5018599999999998 ZT12-15 3.70377 3.70377 3.70377 ZT16-19 4.416024999999999 4.416024999999999 4.416024999999999 ZT20-23 2.891775 2.891775 2.891775