Skip main navigation

Scatter charts and correlation

In this article, Paula describes what a Scatter plot is and how to read one.
Scatter Charts And Correlation
© Paula Guilfoyle

What are Scatter Plots?

A Scatter plot is used to visualize relationships between two or more variables.

A relationship between two values is known as correlation. You can have a positive correlation. You can have a negative correlation. And you can have no correlation.

Testing for correlation is useful when you want to establish if there are possible connections between two variables.

A scatter plot can also be useful for identifying other patterns in data. We can divide data points into groups based on how closely sets of points cluster together.

Scatter plots can also show if there are any unexpected gaps in the data and if there are any outlier points.

How to read a Scatter Chart

Correlation can be charted as shown below. Where one variable is charted against a second in a scatter plot. A strong positive correlation will show a line or curve increasing as you move right across the chart. This can be seen in 1 below.

A strong negative correlation will show a line or curve decreasing as you move right across the chart. This can be seen in 4 below (bottom-right).

4 different scatter charts showing different types of correlation

For a better view of the above image, see the PDF attached.

When a scatter plot is used to look at a predictive or correlational relationship between variables, it is common to add a trend line. This trend line is the mathematical best fit for the data. This can provide an additional sign as to how strong the relationship between the two variables is. And it also shows if there are any unusual points affecting the computation of the trend line.

Example of an Excel scatter chart

© Paula Guilfoyle
This article is from the free online

Introduction to Excel Charts for Data Visualisation

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education