condition mean min max ZT0-3 20.944742 20.944742 20.944742 ZT4-7 17.485636 17.485636 17.485636 ZT8-11 16.606355999999998 16.606355999999998 16.606355999999998 ZT12-15 16.493437999999998 16.493437999999998 16.493437999999998 ZT16-19 12.902325999999999 12.902325999999999 12.902325999999999 ZT20-23 12.8052685 12.8052685 12.8052685