condition mean min max ZT0-3 20.709672 20.709672 20.709672 ZT4-7 18.8143575 18.8143575 18.8143575 ZT8-11 18.3624625 18.3624625 18.3624625 ZT12-15 17.8022235 17.8022235 17.8022235 ZT16-19 17.801233500000002 17.801233500000002 17.801233500000002 ZT20-23 19.462921 19.462921 19.462921