What is a Venn diagram?
A Venn diagram shows the similarities and differences of two or more data sets by using overlapping circles. (In the context of Venn diagrams, a ‘set’ is simply a collection of objects.) The overlapping areas show the similarities and the non-overlapping areas show the differences. Venn diagrams are particularly useful for showing the logical relationship between data sets.
For example, you could compare electric cars and gasoline-powered cars - a circle for each one. The two circles would overlap in the middle showing the number of hybrid cars that can operate on both gasoline AND an electric charge.
Although Venn diagrams can have unlimited circles (each circle representing a data set), they usually have just two or three overlapping circles (any more than three circles/data sets becomes quite complex).
Venn diagrams may also be called primary diagrams, set diagrams, or logic diagrams. It’s worth noting that Venn diagrams are not always quantitative - sometimes they’re purely illustrative for showing intersections between groups.
What is an example of a Venn diagram?
Here’s a straightforward example of a Venn diagram. Suppose you want to see the relationship between books available in hardcopy and books available on Kindle. There are a total of 45 books - 18 available in hard copy, 15 available on Kindle, and 12 books available in both formats.
By drawing two circles that overlap, you can see the relationship between the two sets of data (hard copy books and Kindle books). The similarity (books available in both formats) is shown in the middle overlapping section.
Venn diagrams can become much more complex with more data sets (creating additional circles) and are often shaded to help better visualize the relationships between data sets.