condition mean min max ZT0-3 20.607582 20.607582 20.607582 ZT4-7 20.190533 20.190533 20.190533 ZT8-11 16.6689055 16.6689055 16.6689055 ZT12-15 15.5973435 15.5973435 15.5973435 ZT16-19 15.971650499999999 15.971650499999999 15.971650499999999 ZT20-23 16.177092 16.177092 16.177092