A box and whisker plot is a graph that presents the distribution of a category of data.
Typically, box and whisker plots break the data into four or five points. Four point, or quartile boxplots, present the “box” as defined by the first and third quartile. The median value is also depicted in the box and the “whiskers” represent the minimum and maximum values in the data.
In a five point, or quintile boxplot, the points are the minimum. Presenting data in this way is useful for indicating whether a distribution is skewed and whether there are potential outliers in the data. Box and whisker plots are also useful for comparing two or more datasets and for representing a large number of observations.
Box and whisker plots can be displayed horizontally or vertically and displayed side-by-side for comparisons.
Clearly label median, lower and upper quartiles, lowest and highest observations.
Include a box centered on the median with left/bottom side ending at the lower quartile and right/top side at the upper quartile.
Include a horizontal line running through the center of the box beginning at the lowest observation and ending at the highest observation
Never use a box and whisker plot to represent dissimilar data.
Use bar charts when comparing large changes in data values.
Don’t remove outliers without making note of it.