condition mean min max ZT0-3 6.041895 6.041895 6.041895 ZT4-7 2.22365 2.22365 2.22365 ZT8-11 4.504005 4.504005 4.504005 ZT12-15 6.93741 6.93741 6.93741 ZT16-19 7.706645 7.706645 7.706645 ZT20-23 9.09636 9.09636 9.09636