condition mean min max ZT0-3 21.887275 21.2185 22.55605 ZT4-7 16.68535 16.68535 16.68535 ZT8-11 17.8243 17.8243 17.8243 ZT12-15 0 0 0 ZT16-19 21.23005 21.23005 21.23005 ZT20-23 21.1418 21.1418 21.1418