Can we draw a trend line in case of a nonlinear association?
See solution.
Practice makes perfect
We want to describe the difference between the scatter plot of a nonlinear association and that of a linear association. Before we do that, let's review all of the types of associations between two data sets that can be shown using scatter plots.
Remember that there can be no association between two data sets, which means that the two measures are not related. Now, let's focus on linear association. To do this we will take a look at the example scatter plot of a negative linear association.
In the case of a linear association, points lie close to a line and we are able to draw a line that shows the association between the data points. This line is called a trend line.
When a scatter plot presents a linear association, this means that the x-values and y-values change in an approximately proportional way. Additionally, if we have a linear association we are able to write an equation for this relationship. Now, let's move to the example of a nonlinear association.
We can see that points in a nonlinear association do not form a line, so we cannot draw a trend line. This suggests that the relationship between the x-values and the y-values is not proportional.
