condition mean min max ZT0-3 8.817977 8.817977 8.817977 ZT4-7 7.681938499999999 7.681938499999999 7.681938499999999 ZT8-11 7.9359595 7.9359595 7.9359595 ZT12-15 7.6216775 7.6216775 7.6216775 ZT16-19 7.5797345 7.5797345 7.5797345 ZT20-23 7.7208369999999995 7.7208369999999995 7.7208369999999995