A box plot is a type of plot that displays the five number summary of a dataset, which includes:
- The minimum value
- The first quartile (the 25th percentile)
- The median value
- The third quartile (the 75th percentile)
- The maximum value
To make a box plot, we first draw a box from the first to the third quartile.
Then we draw a vertical line at the median.
Lastly, we draw “whiskers” from the quartiles to the minimum and maximum value.
To find the median of a box plot, we simply need to identify the value located at the vertical line inside of the box.
The following examples show how to find the median of a box plot in practice.
Example 1: Exam Scores
The following box plot shows the distribution of scores on a certain college exam.
What is the median of the exam scores?
To find the median, we need to identify the vertical line inside the box.
We can then find what value lines up with this vertical line on the number line:
The median of the exam scores is about 76.
Example 2: Points Scored
The following box plot shows the distribution of points scored by basketball players in a certain league.
What is the median of the distribution?
To find the median, we need to identify the vertical line inside the box.
We can then find what value lines up with this vertical line on the number line:
The median of the distribution is about 21.
Example 3: Comparing Plant Heights
The following box plots show the distribution of heights for two different plant species: Red and Blue.
Which distribution has a higher median value?
The median of the red box plot is about 28.
The median of the blue box plot is about 21.
Thus, the red plant species has a higher median value.
Additional Resources
The following tutorials provide additional information about box plots:
Box Plot Generator
How to Compare Box Plots
How to Identify Skewness in Box Plots
How to Find the Interquartile Range of a Box Plot