condition mean min max ZT0-3 13.672326 13.672326 13.672326 ZT4-7 16.798924 16.798924 16.798924 ZT8-11 19.3238795 19.3238795 19.3238795 ZT12-15 21.113920999999998 21.113920999999998 21.113920999999998 ZT16-19 18.3125015 18.3125015 18.3125015 ZT20-23 20.292495 20.292495 20.292495