condition mean min max ZT0-3 8.890904 8.890904 8.890904 ZT4-7 8.249487 8.249487 8.249487 ZT8-11 7.9688735 7.9688735 7.9688735 ZT12-15 8.1898315 8.1898315 8.1898315 ZT16-19 8.7223075 8.7223075 8.7223075 ZT20-23 7.8734135 7.8734135 7.8734135