condition mean min max ZT0-3 4.031955 2.27127 4.94753 ZT4-7 1.871245 1.871245 1.871245 ZT8-11 2.6330999999999998 2.6330999999999998 2.6330999999999998 ZT12-15 2.659735 2.58194 2.73753 ZT16-19 2.62059 2.62059 2.62059 ZT20-23 2.9491899999999998 2.9491899999999998 2.9491899999999998