What is a Box and Whisker Plot?

Answer 1

The box and whiskers plot is a means to illustrate data. This is a chart where the horizontal axis represents the possible values that a variable can take. The vertical axis is irrelevant.

5 key statistics are extracted from the data set: the minimum value, the lower quartile, the median, the upper quartile and the maximum value.

The plot consists of a box or rectangle whose left side is the lower quartile and whose right is the upper quartile. The height of the rectangle is an arbitrary value. The median appears as a vertical line in this rectangle.

From the middle of the left side, a horizontal line stretches out to the minimum value. Similarly, a line to the maximum value goes from the right end of the rectangle. These are the whiskers.

That is the basic box and whiskers plot.

One refinement is to exclude outliers, determine the whisker-ends without them and then mark them separately as "X" along where the whiskers would have extended to.

Answer 2

A Box and Whisker Plot are always uniform in their use of a box. It is simply a way of graphically depicting groups of numerical data. There can be several forms of this and different shapes.