How to Make and Interpret a Boxplot
by Dean, Pooja, and Greg
First you have to survey a topic of your choice or given topic. In our study we got backpack weights and student weights. After you collect the data, you put them in order from least to greatest. For Example: Take these numbers
13, 8, 3, 14, 80, 5, 72, 30, 8, and
1.
This is what they look like in order from least to greatest:
1, 3, 5, 8, 8, 13, 14, 30, 72, and then 80.
Now it might be harder if you have TONS of data, like we did.
Next you must find the "Five Number Summary" which contains:
Minimum: The smallest number in the data set
Median: The middle of the entire list of numbers
Q1: The middle number in the first half of the data set (first quartile)
Q3: The middle number in the second half of the data set (third quartile)
Maximum: The biggest number in the data set
First:
find the Minimum and Maximum
After that: find the Median. If the median falls in between two numbers
it would be whatever the average of those numbers is. (Click
here for a lesson on how to find the median.)
Next: you need to find the Q1 and Q3. To do this you first need
to split the data in half. Then find the Q1 by finding the middle of the
first split section. (Click here for a lesson
on how to find the Q1 and Q3.)
Here is the Box Plot that results from this data:
The Q1 and Q3 mark the beginning and ending of the "box" that is drawn. (50% of the data lie within the box.)
The minimum and maximum values create the "whiskers" that you see on the boxplot.
The "median" will be shown somewhere inside the box.
The asterisks *** show "outliers" which represent numbers that lie way beyond the minimum and maximum. Click here for a lesson on "outliers."
