condition mean min max ZT0-3 6.045885 6.045885 6.045885 ZT4-7 7.487485 7.487485 7.487485 ZT8-11 6.309965 6.309965 6.309965 ZT12-15 5.230725 5.230725 5.230725 ZT16-19 7.7574749999999995 7.7574749999999995 7.7574749999999995 ZT20-23 8.257495 8.257495 8.257495