he causal effect *b*~*xy*~ is set to either 0, or some value such that *x* explains 00% of the variance in *y*. Values for *e*~*u*0~,*e*~*x*~, and *e*~*y*~ are sampled from normal distributions with mean 0 and variances that are scaled to satisfy the variances of all other parameters described for the model. 