condition mean min max ZT0-3 7.920182 7.920182 7.920182 ZT4-7 7.426733 7.426733 7.426733 ZT8-11 7.691235 7.691235 7.691235 ZT12-15 8.151752 8.151752 8.151752 ZT16-19 7.718226 7.718226 7.718226 ZT20-23 7.0714675 7.0714675 7.0714675