# The (box) plot thickens…

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- The (box) plot thickens…

## The (box) plot thickens…

Recently the *CM Define It* app featured the term *box plot*. A box plot (also known as a *box-and-whisker plot*, *boxplot* or *box-plot*) is a graph which summarises data based on quartiles, thus splitting the data into fourths (Tu, 2016).

We thought we’d take a look at how popular this term has been over time using Google Books Ngram Viewer.

Figure 1. Frequency of use of the term box plot over time, as a percentage of words in books indexed by Google Books.

Why is there such a sharp increase in the appearance of the term box plot since the late 1970s? In 1970, John Tukey introduced the box-and-whisker plot as a tool in exploratory data analysis (Tukey, 1970). In 1977, he published a book titled *Exploratory Data Analysis*, which presented the box plot to the world and has been widely cited and used ever since. This could explain why such a steep increase occurred from the late 1970s.

In 1952, Spear established the basic graphic box plot form, including the range bars (Spear, 1952, as cited in Wickham & Stryjewski, 2011). Despite this, there is no increase in the frequency of the appearance of the term box plot in books at that time. The graph, however, shows a spike around 1810 and another from 1820 to 1830. We couldn’t find a clear explanation for this increase!

Interestingly, when we changed the word in the NGram Viewer to boxplot, the spike around the early 1800s disappeared!

Figure 2. Frequency of the word boxplot over time, as a percentage of words in books indexed by Google Books.

Can you explain why there are two spikes in the early 1800s when the term box plot is considered? Do you know why the spikes disappear when the word *boxplot* is input instead? If so, get in touch with us by commenting below or by emailing us.

Please sign up or continue to use the *CM Define It* app, which will help us gain insight into what makes powerful mathematical definitions and will inform the glossary in the Cambridge Mathematics Framework.

**References:**

Tu, R. (2016, November 29). *Box-and-whisker plot*. Website. https://www.britannica.com/science/box-and-whisker-plot

Tukey. J. W. (1970). *Exploratory data analysis* (preliminary edition). Addison–Wesley.

Tukey, J. W. (1977). *Exploratory data analysis*. Addison-Wesley.

Wickham, H. & Stryjewski, L. (2011). *40 years of boxplots*. https://vita.had.co.nz/papers/boxplots.pdf

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