When constructing a box and whisker, we need to know the minimum value of the set of data, the maximum value, the first quartile (the middle value of the lower half of the data), the median (the middle value of the set of data when arranged from lowest to highest), the third quartile (the middle value of the upper half of the data) and the maximum value. An example of a box and whisker is shown with these five values identified.  Notice the box drawn enclosing
the first quartile, the median and the third quartile.