condition mean min max ZT0-3 7.61457 7.61457 7.61457 ZT4-7 8.637421 8.637421 8.637421 ZT8-11 8.5420965 8.5420965 8.5420965 ZT12-15 9.4388375 9.4388375 9.4388375 ZT16-19 10.7364525 10.7364525 10.7364525 ZT20-23 8.779859 8.779859 8.779859