condition mean min max ZT0-3 15.341971 15.341971 15.341971 ZT4-7 15.868708999999999 15.868708999999999 15.868708999999999 ZT8-11 15.1920645 15.1920645 15.1920645 ZT12-15 14.407810000000001 14.407810000000001 14.407810000000001 ZT16-19 15.242663499999999 15.242663499999999 15.242663499999999 ZT20-23 16.4363785 16.4363785 16.4363785