7. Exercise 6 in Chapter 4 was “designed to explore further the nature of common causes, and what happens when non-common causes are included in a multiple regression. We will begin our analysis of these data here, and will return to them in Part 2 when we have the tools to explore them more completely.”

You now have the tools to explore them more completely. To review, there are two data files for this exercise, both including variables labeled X1 X2 X3 and Y1. In both files, the three X variables are intercorrelated, but variable X2 is not a common cause of variables Y1 and X3. For the data in the first file (common cause 1.sav), variable X2 has no effect on Y1. In the second file (common cause 2.sav), variable X2 has no effect on variable X3.