Researching interaction between variables – scatterplots

What if we are interested not in a single variable but in how different variables depend on each other? Well in this case we have scatterplots – good for looking at interaction between two variables.

Look at the sample scatterplot above: we have one numerical value on the X and another numerical value on the Y axis. The dots are one data point. This plot has certain shortcomings as well: The dots overlap and thus if there are a lot of dots you don’t really see where they are. This could be solved by adding transparency or by selecting a specific range to show. Nevertheless one trend becomes clear: Above a certain life expectancy, health care costs suddenly increase dramatically. Also notice the three single dots on the lower left? Interesting outliers – we’ll look at them in a later module.