condition mean min max ZT0-3 7.072405 4.05186 12.16565 ZT4-7 2.774905 2.774905 2.774905 ZT8-11 8.26375 8.26375 8.26375 ZT12-15 13.62242 10.21874 17.0261 ZT16-19 20.58635 20.58635 20.58635 ZT20-23 6.287765 6.287765 6.287765