condition mean min max ZT0-3 19.365388 19.365388 19.365388 ZT4-7 21.1348425 21.1348425 21.1348425 ZT8-11 20.2394295 20.2394295 20.2394295 ZT12-15 22.264067500000003 22.264067500000003 22.264067500000003 ZT16-19 20.880191500000002 20.880191500000002 20.880191500000002 ZT20-23 21.6089385 21.6089385 21.6089385