condition mean min max ZT0-3 21.365925 20.4356 22.29625 ZT4-7 11.7016 11.7016 11.7016 ZT8-11 15.76755 15.76755 15.76755 ZT12-15 0 0 0 ZT16-19 15.933349999999999 15.933349999999999 15.933349999999999 ZT20-23 23.39935 23.39935 23.39935