How to find an interquartile range on a boxplot

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Finding an interquartile range on a boxplot is easy! (If you only have numbers, see How to  find an interquartile range from a set of numbers). This how-to will show you how to find an interquartile range in a couple of easy steps.

Let’s find the interquartile range for the above graph.

• Step 1: Find Q1.Q1 is represented on a boxplot by the left hand edge of the “box”.

In the above graph, Q1 is approximately 2.5. (If you are interested, a better explanation of what Q1 is can be found in this article on finding the five number summary.)

• Step 2: Find Q3.
Q3 is represented on a boxplot by the right hand edge of the “box”.

Q3 is approximately 12 in this graph.
• Step 3: Subtract the number you found in step 1 from the number you found in step 3.
This will give you the interquartile range. 12 – 2.5 = 9.5.

11 thoughts on “How to find an interquartile range on a boxplot”

1. Christine Mao

This article was simple to comphrehend. The diagram and the steps explain everything you would need to know. I was able to understand more of the interquartile range on a boxplot. The book helped, but the article was more helpful.

2. Lisa Barcomb

I understood this article it was easy because of the diagram, its nice when you have the diagrams to look at and see what you are doing. But the interquartile range is alittle difficult by plotting it on the boxplot.

3. Vanessa DuBarry

Very easy to learn this. Thanks for this blog!, its just way easier than the book explains it.

4. crystal lydick

Our book does not seem to explain innterequartile range as easily to me as our practically cheating book has. I do not understand our book as I do the practically cheating book.