condition mean min max ZT0-3 0.304566 0.304566 0.304566 ZT4-7 0.3784785 0.3784785 0.3784785 ZT8-11 0.20962999999999998 0.20962999999999998 0.20962999999999998 ZT12-15 0.2647115 0.2647115 0.2647115 ZT16-19 0.449752 0.449752 0.449752 ZT20-23 0.229826 0.229826 0.229826