condition mean min max ZT0-3 1.732655 1.732655 1.732655 ZT4-7 1.755915 1.755915 1.755915 ZT8-11 1.6666050000000001 1.6666050000000001 1.6666050000000001 ZT12-15 1.3761 1.3761 1.3761 ZT16-19 2.1804 2.1804 2.1804 ZT20-23 1.090274 1.090274 1.090274