We are asked to describe how a trend line describes the strength of the association. To do this, let's take a look at the example scatter plot that shows a linear association. We will draw a trend line to better visualize this association.
Recall that the distance of the data points from the trend line tells us about the strength of the association. Here, points lie close to the trend line. This means that the association is strong. Next, let's take a look at the other example scatter plot.
This time points are farther from the trend line, so the association is weaker. Let's summarize what we found out.
Position of Points
Strength of Association
Points are close to the trend line.
Strong
Points are far away from the trend line.
Weak
Notice that we can draw a trend line only in case of linear relationships.
Extra
Types of Associations Between Data Sets
We can review different types of associations between two data sets that can be shown using scatter plots.
Notice that, apart from the linear associations, the association between two data sets can be nonlinear. Additionally, there can be no association between two data sets, and this means that two measures are not related with each other.
