condition mean min max ZT0-3 8.84364 8.84364 8.84364 ZT4-7 8.6589365 8.6589365 8.6589365 ZT8-11 8.721359499999998 8.721359499999998 8.721359499999998 ZT12-15 8.5915875 8.5915875 8.5915875 ZT16-19 7.698216 7.698216 7.698216 ZT20-23 7.866303 7.866303 7.866303