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)