Working with Box Plots

About Box Plots

A box plot represents the distribution of data values by using rectangular box and lines called whiskers.

Parts of a Box Plot

Parts of a Box Plot shows a diagram of a box plot. The bottom and top edges of the box indicate the interquartile range (IQR). That is, the range of values that are between the first and third quartiles (the 25th and 75th percentiles). The marker inside the box indicates the mean value. The line inside the box indicates the median value.

Then the whiskers (lines protruding from the box) indicate the range of values that are outside of the interquartile range but are close enough not to be considered outliers.

Note: If you disable the Show Outliers property, then the whiskers extend to the maximum and minimum values in the plot.

Outliers are data points whose distance from the interquartile range is greater than 1.5 times the size of the interquartile range.

If there are a large number of outlier points, then the range of outlier values is represented by a bar. The data tip for the bar displays additional information about the outlier points. To explore the outlier values, double-click the outlier bar to view the values as a new histogram visualization.

Specify Properties for a Box Plot

On the Properties tab, you can specify the following options:

Name

specifies the name of the visualization.

Title

specifies the title that appears above the graph.

Note: The Title option is disabled if you select Generate graph titles.

Generate graph titles

specifies that the graph title is generated automatically based on the data items in the visualization.

Show grid lines

displays grid lines for each tick on the response axis.

Box direction

specifies whether the boxes are vertical or horizontal.

Overview

specifies whether the chart overview is enabled.

Measure layout

specifies whether the measures share a single response axis (Shared axis) or have separate response axes for each measure (Separate axes).

Note: The Measure layout option is disabled if your visualization contains exactly one measure.

Show averages

displays the mean value as a marker inside the box.

Show outliers

shows outlier points outside of the whiskers. Outliers are data points whose distance from the interquartile range is greater than 1.5 times the size of the interquartile range.

Rotate axis labels

displays the category labels at an angle.

Note: The Rotate axis labels option has no effect if the box plot contains no categories.

Data Roles for a Box Plot

The basic data roles for a box plot are categories and measures. You can assign one category only, and the values of the category are plotted on the category axis. You can assign many measures, and the measure values are plotted on the response axis. At least one measure is required.

In addition to the basic data roles, you can assign these roles:

Lattice columns

creates a lattice of charts, with a column for each value of the category data item that you assign.

Lattice rows

creates a lattice of charts, with a row for each value of the category data item that you assign.