Definition
A Scatter Plot is a diagram that uses pairs of coordinates to show corresponding values from a dataset plotted against a horizontal and vertical axis. Scatter plots are ideal for identifying relationships or trends in sets of data that might not be obvious if they were viewed in just tabular form.
Scatter plots are sometimes also referred to as scatter graphs, scatter charts, or scatter diagrams.
Example of a Scatter Plot
The example below shows measurements of annual global temperature over the last 130 years. Notice that the points are not joined in a scatter plot.
This example shows temperatures generally increasing over time. In terms of the data shown on this scatter plot this is a positive correlation.
Positive Correlations show an upward trend moving from left to right on the horizontal axis/
Observed Average Annual Global Temperatures (NASA data)
Outliers
Scatter plots are good at identifying data that does not fit with the general pattern or relationship. Such data could arise for a number of reasons; it might be the result of an error, or it might be the result of a certain combination of circumstances. Look at the example below where some of the outliers have been identified.
Another Example of a Scatter Plot
The above scatter plot shows the percentage of people who click on links to the HelpingWithMath.com website in the Google search results against the position the link is in the results page (position 1 is the top of the search results). As you might expect, the percentage of people who click drops as the links drop lower on the search result page.
Looking again at the highlighted outliers, this scatter plot could help HelpingWithMath.com to identify where changes to the wording and description of links could be made to get closer to the expected percentage of people to click on them.
Positive or Negative Correlation?
The first scatter plot example showing global temperature change over time showed a positive correlation. The second HelpingWithMath.com website example shows a negative correlation of the coordinate pairs. The value on the vertical axis drops as the value along the horizontal axis decreases.
