condition mean min max ZT0-3 20.631848 20.631848 20.631848 ZT4-7 20.3744055 20.3744055 20.3744055 ZT8-11 21.7460465 21.7460465 21.7460465 ZT12-15 20.847559500000003 20.847559500000003 20.847559500000003 ZT16-19 21.2314375 21.2314375 21.2314375 ZT20-23 18.0861575 18.0861575 18.0861575