Book Image

Data Analysis with STATA

Book Image

Data Analysis with STATA

Overview of this book

Table of Contents (16 chapters)
Data Analysis with Stata
About the Author
About the Reviewers

Box plots

Another way to look at data is box plots; they are also called box and whiskers plots.

In box plots, a box ranges from a quartile in the lower range, which is also 25th percentile of data, to a quartile in the upper range, which is the 75th percentile. It also contains a line in the median value, which is the 50th percentile.

Then, you have whiskers plots. Whiskers generally range from the quartile with a low value and a low adjacent value to the quartile in the upper range and upper adjacent value.

Lower Adjacent Value = lower quartile – 3/ 2 IQR

Upper Adjacent Value = upper quartile + 3/2 IQR

Observations after the lower and upper adjacent value are plotted in terms of points; for example, take a look at the following:

graph box scores

The output of this command is shown in the following figure:

You can divide these graphs by categorical variables; for example, take a look at the following:

 –graph box scores, over(sex)