condition mean min max ZT0-3 7.457014 7.457014 7.457014 ZT4-7 7.033005 7.033005 7.033005 ZT8-11 6.7630615 6.7630615 6.7630615 ZT12-15 7.5596630000000005 7.5596630000000005 7.5596630000000005 ZT16-19 6.7065085 6.7065085 6.7065085 ZT20-23 7.7652425 7.7652425 7.7652425