The box plot (sometimes called a box and whisker plot or box chart) is a graphical
representation of key values from summary statistics. Typically, the values
represented are the minimum, 25th percentile, median, 75th
percentile, and the maximum. Sometimes these values are called the five-number
Figure 1: Values represented in Origin's default Box Plot
Additional values are represented in Origin's default box chart. These include
the 1st and 5th percentiles, mean, and 95th
and 99th percentiles.
Box and Whiskers Plot Examples
Example plots from our Graph
[click on the image to see original graph]
Figure 2: Box chart using the 'diamond
box' option with data and normal curve overlay
Figure 3: Box chart employing an incrementing
custom color list for the box fill option
Box plots are helpful in Quality Analysis for interpreting
the distribution of data since it can easily show whether the data is
skewed and if there are unusual observations (outliers) in the dataset.
Box plots are also very useful when large numbers of observations are
involved and when two or more datasets are being compared.
Box and Whisker Plot Options
Box Display Type : Display for the Box chart can include the box and/or the actual data in a column scatter plot. Display options are as follows:
- Box + Data (overlapped, data on right/left)
When the data is included, its bin values (bin size, begin, end) can be altered. Display of the data can be snapped into bins. Also, a distribution curve can be superimposed on the data.
When the data is displayed as a column scatter, the data can be plotted using its specific Y values. Alternatively, the data can be organized into bins.
Box Options: Although the default box chart is generated
using the upper and lower quartiles, it can easily be changed to one of
the following and saved to the box chart template for future use:
- standard deviation
- standard error
- 25th/75th percentiles (default)
- 10th/25th/75th/90th percentiles
- a constant value
- notched box (notches on the box represent the confidence interval
about the median value)
Whisker Range Options: Although the range represented by
the whiskers in Origin's default box and whisker diagram is between the
5th and 95th percentiles, it can be changed to any of the following and
saved as the default in the box chart template:
- 5-95 (default)
- standard deviation
- standard error
- min/max (extremes)
Several of the options enable the use of a Coefficient field.
If you select Outlier and accept the default coefficient value (1.5),
the whisker length defines what are commonly referred to as the upper
inner and lower inner fence values (a coefficient
= 3 would define what are commonly referred to as the upper outer
and lower outer fences).
Upper Inner Fence = 75th Percentile + (1.5 * Interquartile
Lower Inner Fence = 25th Percentile - (1.5 * Interquartile
Data points that lie outside of the fence values are considered to be
outliers. An Outliers check box is provided to allow you
to display these outliers as individual data points.
- A Diamond Box option is provided.
- Labels can be associated with Box and Whisker Range values.
- Formatting for the Minimum, Maximum, 1%, 99%, and Mean value symbols/data points can be updated.
Basic Data Plot Properties
The following basic data plot properties can be edited in a Box
and Whisker diagram depending on the Box and/or Whisker range settings:
- Symbol Properties: shape, interior, size, and color (more...*)
- Line Properties: style, width, and color (more...*)
- Fill Properties: color, pattern (more...*)
- Pattern Properties: border style, width, and color; pattern
width and color (details are the same as those for Line Properties)
All can be updated quickly and easily through Plot Details, an intuitive
to view the details of a specific graph type.