This more complex scatterplot nicely illustrates the difference in the correlation between height and weight for males and females. Let’s move on to a more complicated example.
Overlay Scatterplots
Another kind of scatterplot that might be useful is one that displays the association between different independent variables with the same dependant variable. Above, we compared the same correlation for different groups. This time, we want to compare different correlations. Let’s use the course evaluation example from the text . It looks like expected grade is more strongly related to ratings of fairness of the exam than ratings of instructor knowledge is related to the exam. I’d like to plot both correlations. I can reasonably plot them on the same graph since all of the questions were rated on the same scale.
Open courseevaluation.sav. You do not need to save HeightWeight.sav since you did not change it. So click No.
Edit the graph to suit your style as you learned in Chapter 3 (e.g., add a title, change the axes titles and legend).