condition mean min max ZT0-3 6.1025925 5.7924299999999995 6.412755000000001 ZT4-7 6.92066 6.92066 6.92066 ZT8-11 7.4153649999999995 7.4153649999999995 7.4153649999999995 ZT12-15 0 0 0 ZT16-19 7.4120099999999995 7.4120099999999995 7.4120099999999995 ZT20-23 7.8052 7.8052 7.8052