Box Plot

http://itl.nist.gov/div898/handbook/eda/section3/boxplot.htm
A box plot (also known as a box-and-whiskers diagram) is a convenient way to categorize numerical data via their five number summaries: the smallest observation (sample minimum), lower quartile (Q1), median (Q2), upper quartile (Q3), and largest observation (sample maximum). Outliers may also be shown on a box plot. Box plots can be featured vertically, or horizontally. Box plots are generally used to show differences in population, but without making any assumptions.
The box plot above compares four machines for energy output.