Scatterplot Example
What is the relationship between students’ achievement motivation and GPA?
In this example, the relationship between students’ achievement motivation
and their GPA is being investigated.
The table on the left includes a small group of individuals for whom GPA and
scores on a motivation scale have been recorded. GPAs can range from 0 to 4
and motivation scores in this example range from 0 to 100. Individuals in
this table were ordered based on their GPA.
Simply looking at the table shows that, in general, as GPA increases,
motivation scores also increase.
However, with a real set of data, which may have hundreds or even
thousands of individuals, a pattern cannot be detected by simply looking at
the numbers. Therefore, a very useful strategy is to represent the two
variables graphically to illustrate the relationship between them.
A graphical representation of individual scores on two variables is called a
scatterplot.
The image on the right is an example of a scatterplot and displays the data
from the table on the left. GPA scores are displayed on the horizontal axis
and motivation scores are displayed on the vertical axis.
Each dot on the scatterplot represents one individual from the data set. The
location of each point on the graph depends on both the GPA and motivation
scores. Individuals with higher GPAs are located further to the right and
individuals with higher motivation scores are located higher up on the graph.
Sam, for example, has a GPA of 2 so his point is located at 2 on the right. He
also has a motivation score of 12, so his point is located at 12 going up.
Scatterplots are not meant to be used in great detail because there are
usually hundreds of individuals in a data set.