Box plot

In descriptive statistics, a box plot is a convenient way of graphically depicting the five-number summary, which consists of the smallest observation, lower quartile, median, upper quartile and largest observation.

The box plot may also identify outliers and possibly the mean.

A plain-text version might look like this:

                            +-----+-+
  *           o     --------|   + | |----
                            +-----+-+

+---+---+---+---+---+---+---+---+---+---+
0   1   2   3   4   5   6   7   8   9  10

For this data set (values are approximate, based on the figure):

• smallest observation (minimum) = .5
• lower quartile = 7
• median = 8.5
• upper quartile = 9
• largest observation (maximum) = 10
• mean = 8
• the value 3.5 is a "mild" outlier
• the value .5 is an "extreme" outlier
• the smallest value that is not an outlier is 5
• the data is skewed to the left (negatively skewed)