condition mean min max ZT0-3 22.808937 22.808937 22.808937 ZT4-7 20.7974915 20.7974915 20.7974915 ZT8-11 20.2258705 20.2258705 20.2258705 ZT12-15 21.526034 21.526034 21.526034 ZT16-19 21.689329999999998 21.689329999999998 21.689329999999998 ZT20-23 19.036288 19.036288 19.036288