condition mean min max ZT0-3 3.185585 2.806725 3.416545 ZT4-7 4.76568 4.76568 4.76568 ZT8-11 7.598955 7.598955 7.598955 ZT12-15 14.670425 13.125 16.21585 ZT16-19 11.76465 11.76465 11.76465 ZT20-23 6.831099999999999 6.831099999999999 6.831099999999999