condition mean min max ZT0-3 6.811795 5.096385 8.527205 ZT4-7 4.0087399999999995 4.0087399999999995 4.0087399999999995 ZT8-11 8.287725 8.287725 8.287725 ZT12-15 0 0 0 ZT16-19 12.576699999999999 12.576699999999999 12.576699999999999 ZT20-23 5.097575 5.097575 5.097575