condition mean min max ZT0-3 8.516425 8.516425 8.516425 ZT4-7 7.891655 7.891655 7.891655 ZT8-11 7.7025255 7.7025255 7.7025255 ZT12-15 7.5110715 7.5110715 7.5110715 ZT16-19 8.092751 8.092751 8.092751 ZT20-23 8.2671435 8.2671435 8.2671435