Analyze these data using an SEM program. For both data sets, the model you should estimate is illustrated in Figure 13.13. Compute and examine the correlations among the variables in both data sets. All correlations are statistically significant, correct?

Now analyze the model shown for both data sets. Notice that for data set 1 the effect of X2 on Y1 is essentially zero. For data set 2, what is the effect of X2 on X3? Is X2 a common cause of X3 and Y1 in either model? Now notice the effect of X3 on Y1 in each model. What should happen to this path when the variable X2 is removed from the model?