condition mean min max ZT0-3 7.556150000000001 6.9700050000000005 8.142295 ZT4-7 6.994835 6.994835 6.994835 ZT8-11 8.219085 8.219085 8.219085 ZT12-15 0 0 0 ZT16-19 8.896764999999998 8.896764999999998 8.896764999999998 ZT20-23 8.66678 8.66678 8.66678