condition mean min max ZT0-3 5.036505 4.239155 5.833855 ZT4-7 4.52487 4.52487 4.52487 ZT8-11 8.6949 8.6949 8.6949 ZT12-15 0 0 0 ZT16-19 7.097225 7.097225 7.097225 ZT20-23 6.347799999999999 6.347799999999999 6.347799999999999