condition mean min max ZT0-3 21.120532 21.120532 21.120532 ZT4-7 17.333801 17.333801 17.333801 ZT8-11 18.087421499999998 18.087421499999998 18.087421499999998 ZT12-15 16.930268499999997 16.930268499999997 16.930268499999997 ZT16-19 17.8577955 17.8577955 17.8577955 ZT20-23 18.5148425 18.5148425 18.5148425