condition mean min max ZT0-3 18.485936 18.485936 18.485936 ZT4-7 20.2764765 20.2764765 20.2764765 ZT8-11 14.445962999999999 14.445962999999999 14.445962999999999 ZT12-15 14.423716500000001 14.423716500000001 14.423716500000001 ZT16-19 15.032044500000001 15.032044500000001 15.032044500000001 ZT20-23 15.648847 15.648847 15.648847