condition mean min max ZT0-3 7.927695 7.927695 7.927695 ZT4-7 5.965165 5.965165 5.965165 ZT8-11 6.43679 6.43679 6.43679 ZT12-15 7.771855 7.771855 7.771855 ZT16-19 8.996469999999999 8.996469999999999 8.996469999999999 ZT20-23 7.696809999999999 7.696809999999999 7.696809999999999