condition mean min max ZT0-3 17.161555 17.161555 17.161555 ZT4-7 11.534225 11.534225 11.534225 ZT8-11 9.648596 9.648596 9.648596 ZT12-15 9.886985 9.886985 9.886985 ZT16-19 9.391812999999999 9.391812999999999 9.391812999999999 ZT20-23 9.6078715 9.6078715 9.6078715